461 lines
14 KiB
ReStructuredText
461 lines
14 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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=========
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SAS Layer
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=========
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The SAS Layer is a management infrastructure which manages
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SAS LLDDs. It sits between SCSI Core and SAS LLDDs. The
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layout is as follows: while SCSI Core is concerned with
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SAM/SPC issues, and a SAS LLDD+sequencer is concerned with
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phy/OOB/link management, the SAS layer is concerned with:
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* SAS Phy/Port/HA event management (LLDD generates,
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SAS Layer processes),
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* SAS Port management (creation/destruction),
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* SAS Domain discovery and revalidation,
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* SAS Domain device management,
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* SCSI Host registration/unregistration,
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* Device registration with SCSI Core (SAS) or libata
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(SATA), and
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* Expander management and exporting expander control
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to user space.
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A SAS LLDD is a PCI device driver. It is concerned with
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phy/OOB management, and vendor specific tasks and generates
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events to the SAS layer.
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The SAS Layer does most SAS tasks as outlined in the SAS 1.1
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spec.
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The sas_ha_struct describes the SAS LLDD to the SAS layer.
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Most of it is used by the SAS Layer but a few fields need to
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be initialized by the LLDDs.
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After initializing your hardware, from the probe() function
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you call sas_register_ha(). It will register your LLDD with
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the SCSI subsystem, creating a SCSI host and it will
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register your SAS driver with the sysfs SAS tree it creates.
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It will then return. Then you enable your phys to actually
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start OOB (at which point your driver will start calling the
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notify_* event callbacks).
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Structure descriptions
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======================
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``struct sas_phy``
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------------------
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Normally this is statically embedded to your driver's
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phy structure::
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struct my_phy {
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blah;
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struct sas_phy sas_phy;
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bleh;
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};
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And then all the phys are an array of my_phy in your HA
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struct (shown below).
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Then as you go along and initialize your phys you also
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initialize the sas_phy struct, along with your own
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phy structure.
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In general, the phys are managed by the LLDD and the ports
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are managed by the SAS layer. So the phys are initialized
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and updated by the LLDD and the ports are initialized and
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updated by the SAS layer.
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There is a scheme where the LLDD can RW certain fields,
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and the SAS layer can only read such ones, and vice versa.
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The idea is to avoid unnecessary locking.
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enabled
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- must be set (0/1)
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id
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- must be set [0,MAX_PHYS)]
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class, proto, type, role, oob_mode, linkrate
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- must be set
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oob_mode
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- you set this when OOB has finished and then notify
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the SAS Layer.
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sas_addr
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- this normally points to an array holding the sas
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address of the phy, possibly somewhere in your my_phy
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struct.
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attached_sas_addr
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- set this when you (LLDD) receive an
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IDENTIFY frame or a FIS frame, _before_ notifying the SAS
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layer. The idea is that sometimes the LLDD may want to fake
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or provide a different SAS address on that phy/port and this
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allows it to do this. At best you should copy the sas
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address from the IDENTIFY frame or maybe generate a SAS
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address for SATA directly attached devices. The Discover
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process may later change this.
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frame_rcvd
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- this is where you copy the IDENTIFY/FIS frame
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when you get it; you lock, copy, set frame_rcvd_size and
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unlock the lock, and then call the event. It is a pointer
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since there's no way to know your hw frame size _exactly_,
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so you define the actual array in your phy struct and let
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this pointer point to it. You copy the frame from your
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DMAable memory to that area holding the lock.
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sas_prim
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- this is where primitives go when they're
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received. See sas.h. Grab the lock, set the primitive,
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release the lock, notify.
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port
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- this points to the sas_port if the phy belongs
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to a port -- the LLDD only reads this. It points to the
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sas_port this phy is part of. Set by the SAS Layer.
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ha
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- may be set; the SAS layer sets it anyway.
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lldd_phy
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- you should set this to point to your phy so you
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can find your way around faster when the SAS layer calls one
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of your callbacks and passes you a phy. If the sas_phy is
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embedded you can also use container_of -- whatever you
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prefer.
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``struct sas_port``
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-------------------
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The LLDD doesn't set any fields of this struct -- it only
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reads them. They should be self explanatory.
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phy_mask is 32 bit, this should be enough for now, as I
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haven't heard of a HA having more than 8 phys.
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lldd_port
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- I haven't found use for that -- maybe other
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LLDD who wish to have internal port representation can make
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use of this.
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``struct sas_ha_struct``
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------------------------
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It normally is statically declared in your own LLDD
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structure describing your adapter::
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struct my_sas_ha {
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blah;
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struct sas_ha_struct sas_ha;
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struct my_phy phys[MAX_PHYS];
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struct sas_port sas_ports[MAX_PHYS]; /* (1) */
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bleh;
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};
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(1) If your LLDD doesn't have its own port representation.
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What needs to be initialized (sample function given below).
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pcidev
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^^^^^^
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sas_addr
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- since the SAS layer doesn't want to mess with
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memory allocation, etc, this points to statically
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allocated array somewhere (say in your host adapter
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structure) and holds the SAS address of the host
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adapter as given by you or the manufacturer, etc.
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sas_port
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^^^^^^^^
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sas_phy
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- an array of pointers to structures. (see
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note above on sas_addr).
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These must be set. See more notes below.
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num_phys
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- the number of phys present in the sas_phy array,
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and the number of ports present in the sas_port
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array. There can be a maximum num_phys ports (one per
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port) so we drop the num_ports, and only use
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num_phys.
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The event interface::
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/* LLDD calls these to notify the class of an event. */
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void sas_notify_port_event(struct sas_phy *, enum port_event, gfp_t);
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void sas_notify_phy_event(struct sas_phy *, enum phy_event, gfp_t);
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The port notification::
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/* The class calls these to notify the LLDD of an event. */
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void (*lldd_port_formed)(struct sas_phy *);
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void (*lldd_port_deformed)(struct sas_phy *);
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If the LLDD wants notification when a port has been formed
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or deformed it sets those to a function satisfying the type.
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A SAS LLDD should also implement at least one of the Task
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Management Functions (TMFs) described in SAM::
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/* Task Management Functions. Must be called from process context. */
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int (*lldd_abort_task)(struct sas_task *);
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int (*lldd_abort_task_set)(struct domain_device *, u8 *lun);
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int (*lldd_clear_aca)(struct domain_device *, u8 *lun);
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int (*lldd_clear_task_set)(struct domain_device *, u8 *lun);
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int (*lldd_I_T_nexus_reset)(struct domain_device *);
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int (*lldd_lu_reset)(struct domain_device *, u8 *lun);
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int (*lldd_query_task)(struct sas_task *);
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For more information please read SAM from T10.org.
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Port and Adapter management::
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/* Port and Adapter management */
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int (*lldd_clear_nexus_port)(struct sas_port *);
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int (*lldd_clear_nexus_ha)(struct sas_ha_struct *);
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A SAS LLDD should implement at least one of those.
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Phy management::
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/* Phy management */
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int (*lldd_control_phy)(struct sas_phy *, enum phy_func);
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lldd_ha
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- set this to point to your HA struct. You can also
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use container_of if you embedded it as shown above.
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A sample initialization and registration function
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can look like this (called last thing from probe())
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*but* before you enable the phys to do OOB::
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static int register_sas_ha(struct my_sas_ha *my_ha)
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{
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int i;
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static struct sas_phy *sas_phys[MAX_PHYS];
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static struct sas_port *sas_ports[MAX_PHYS];
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my_ha->sas_ha.sas_addr = &my_ha->sas_addr[0];
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for (i = 0; i < MAX_PHYS; i++) {
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sas_phys[i] = &my_ha->phys[i].sas_phy;
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sas_ports[i] = &my_ha->sas_ports[i];
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}
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my_ha->sas_ha.sas_phy = sas_phys;
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my_ha->sas_ha.sas_port = sas_ports;
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my_ha->sas_ha.num_phys = MAX_PHYS;
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my_ha->sas_ha.lldd_port_formed = my_port_formed;
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my_ha->sas_ha.lldd_dev_found = my_dev_found;
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my_ha->sas_ha.lldd_dev_gone = my_dev_gone;
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my_ha->sas_ha.lldd_execute_task = my_execute_task;
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my_ha->sas_ha.lldd_abort_task = my_abort_task;
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my_ha->sas_ha.lldd_abort_task_set = my_abort_task_set;
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my_ha->sas_ha.lldd_clear_aca = my_clear_aca;
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my_ha->sas_ha.lldd_clear_task_set = my_clear_task_set;
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my_ha->sas_ha.lldd_I_T_nexus_reset= NULL; (2)
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my_ha->sas_ha.lldd_lu_reset = my_lu_reset;
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my_ha->sas_ha.lldd_query_task = my_query_task;
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my_ha->sas_ha.lldd_clear_nexus_port = my_clear_nexus_port;
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my_ha->sas_ha.lldd_clear_nexus_ha = my_clear_nexus_ha;
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my_ha->sas_ha.lldd_control_phy = my_control_phy;
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return sas_register_ha(&my_ha->sas_ha);
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}
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(2) SAS 1.1 does not define I_T Nexus Reset TMF.
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Events
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======
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Events are **the only way** a SAS LLDD notifies the SAS layer
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of anything. There is no other method or way a LLDD to tell
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the SAS layer of anything happening internally or in the SAS
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domain.
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Phy events::
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PHYE_LOSS_OF_SIGNAL, (C)
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PHYE_OOB_DONE,
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PHYE_OOB_ERROR, (C)
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PHYE_SPINUP_HOLD.
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Port events, passed on a _phy_::
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PORTE_BYTES_DMAED, (M)
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PORTE_BROADCAST_RCVD, (E)
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PORTE_LINK_RESET_ERR, (C)
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PORTE_TIMER_EVENT, (C)
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PORTE_HARD_RESET.
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Host Adapter event:
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HAE_RESET
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A SAS LLDD should be able to generate
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- at least one event from group C (choice),
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- events marked M (mandatory) are mandatory (only one),
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- events marked E (expander) if it wants the SAS layer
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to handle domain revalidation (only one such).
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- Unmarked events are optional.
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Meaning:
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HAE_RESET
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- when your HA got internal error and was reset.
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PORTE_BYTES_DMAED
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- on receiving an IDENTIFY/FIS frame
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PORTE_BROADCAST_RCVD
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- on receiving a primitive
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PORTE_LINK_RESET_ERR
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- timer expired, loss of signal, loss of DWS, etc. [1]_
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PORTE_TIMER_EVENT
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- DWS reset timeout timer expired [1]_
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PORTE_HARD_RESET
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- Hard Reset primitive received.
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PHYE_LOSS_OF_SIGNAL
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- the device is gone [1]_
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PHYE_OOB_DONE
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- OOB went fine and oob_mode is valid
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PHYE_OOB_ERROR
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- Error while doing OOB, the device probably
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got disconnected. [1]_
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PHYE_SPINUP_HOLD
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- SATA is present, COMWAKE not sent.
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.. [1] should set/clear the appropriate fields in the phy,
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or alternatively call the inlined sas_phy_disconnected()
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which is just a helper, from their tasklet.
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The Execute Command SCSI RPC::
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int (*lldd_execute_task)(struct sas_task *, gfp_t gfp_flags);
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Used to queue a task to the SAS LLDD. @task is the task to be executed.
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@gfp_mask is the gfp_mask defining the context of the caller.
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This function should implement the Execute Command SCSI RPC,
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That is, when lldd_execute_task() is called, the command
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go out on the transport *immediately*. There is *no*
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queuing of any sort and at any level in a SAS LLDD.
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Returns:
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* -SAS_QUEUE_FULL, -ENOMEM, nothing was queued;
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* 0, the task(s) were queued.
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::
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struct sas_task {
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dev -- the device this task is destined to
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task_proto -- _one_ of enum sas_proto
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scatter -- pointer to scatter gather list array
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num_scatter -- number of elements in scatter
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total_xfer_len -- total number of bytes expected to be transferred
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data_dir -- PCI_DMA_...
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task_done -- callback when the task has finished execution
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};
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Discovery
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=========
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The sysfs tree has the following purposes:
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a) It shows you the physical layout of the SAS domain at
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the current time, i.e. how the domain looks in the
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physical world right now.
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b) Shows some device parameters _at_discovery_time_.
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This is a link to the tree(1) program, very useful in
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viewing the SAS domain:
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ftp://mama.indstate.edu/linux/tree/
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I expect user space applications to actually create a
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graphical interface of this.
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That is, the sysfs domain tree doesn't show or keep state if
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you e.g., change the meaning of the READY LED MEANING
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setting, but it does show you the current connection status
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of the domain device.
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Keeping internal device state changes is responsibility of
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upper layers (Command set drivers) and user space.
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When a device or devices are unplugged from the domain, this
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is reflected in the sysfs tree immediately, and the device(s)
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removed from the system.
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The structure domain_device describes any device in the SAS
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domain. It is completely managed by the SAS layer. A task
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points to a domain device, this is how the SAS LLDD knows
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where to send the task(s) to. A SAS LLDD only reads the
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contents of the domain_device structure, but it never creates
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or destroys one.
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Expander management from User Space
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===================================
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In each expander directory in sysfs, there is a file called
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"smp_portal". It is a binary sysfs attribute file, which
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implements an SMP portal (Note: this is *NOT* an SMP port),
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to which user space applications can send SMP requests and
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receive SMP responses.
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Functionality is deceptively simple:
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1. Build the SMP frame you want to send. The format and layout
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is described in the SAS spec. Leave the CRC field equal 0.
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open(2)
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2. Open the expander's SMP portal sysfs file in RW mode.
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write(2)
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3. Write the frame you built in 1.
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read(2)
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4. Read the amount of data you expect to receive for the frame you built.
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If you receive different amount of data you expected to receive,
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then there was some kind of error.
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close(2)
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All this process is shown in detail in the function do_smp_func()
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and its callers, in the file "expander_conf.c".
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The kernel functionality is implemented in the file
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"sas_expander.c".
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The program "expander_conf.c" implements this. It takes one
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argument, the sysfs file name of the SMP portal to the
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expander, and gives expander information, including routing
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tables.
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The SMP portal gives you complete control of the expander,
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so please be careful.
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