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OMAP3: SDRC: Add comments on Errata i520 for Global SW reset

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This patch adds comments on precaution to be taken if Global Warm reset is
used as the means to trigger system reset.

Signed-off-by: Vishwanath BS <vishwanath.bs@ti.com>
[paul@pwsan.com: fixed typos, one mentioned by Sanjeev]
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Sanjeev Premi <premi@ti.com>
This commit is contained in:
Vishwanath BS 2010-10-05 19:35:34 +05:30 committed by Paul Walmsley
parent 60a0e5d972
commit 9bf8391846
1 changed files with 28 additions and 0 deletions
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28
arch/arm/mach-omap2/prcm.c
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@ -74,6 +74,34 @@ void omap_prcm_arch_reset(char mode, const char *cmd)
WARN_ON(1);
}
/*
* As per Errata i520, in some cases, user will not be able to
* access DDR memory after warm-reset.
* This situation occurs while the warm-reset happens during a read
* access to DDR memory. In that particular condition, DDR memory
* does not respond to a corrupted read command due to the warm
* reset occurrence but SDRC is waiting for read completion.
* SDRC is not sensitive to the warm reset, but the interconnect is
* reset on the fly, thus causing a misalignment between SDRC logic,
* interconnect logic and DDR memory state.
* WORKAROUND:
* Steps to perform before a Warm reset is trigged:
* 1. enable self-refresh on idle request
* 2. put SDRC in idle
* 3. wait until SDRC goes to idle
* 4. generate SW reset (Global SW reset)
*
* Steps to be performed after warm reset occurs (in bootloader):
* if HW warm reset is the source, apply below steps before any
* accesses to SDRAM:
* 1. Reset SMS and SDRC and wait till reset is complete
* 2. Re-initialize SMS, SDRC and memory
*
* NOTE: Above work around is required only if arch reset is implemented
* using Global SW reset(GLOBAL_SW_RST). DPLL3 reset does not need
* the WA since it resets SDRC as well as part of cold reset.
*/
/* XXX should be moved to some OMAP2/3 specific code */
omap2_prm_set_mod_reg_bits(OMAP_RST_DPLL3_MASK, prcm_offs,
OMAP2_RM_RSTCTRL);