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drm/i915: Generate 2MHz clock for display port aux channel I/O. Retry I/O.

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The display port aux channel clock is taken from the hrawclk value, which is
provided to the chip as the FSB frequency (as far as I can determine). The
strapping values for that are available in the CLKCFG register, now used to
select an appropriate divider to generate a 2MHz clock.

In addition, the DisplayPort spec requires that each aux channel I/O be
retried 'at least 3 times' in case the sink is idle when the first request
comes in.

Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Keith Packard 2009-06-11 22:31:31 -07:00
parent a5b3da543d
commit fb0f8fbf97
1 changed files with 70 additions and 32 deletions
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52
drivers/gpu/drm/i915/intel_dp.c
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@ -154,6 +154,36 @@ unpack_aux(uint32_t src, uint8_t *dst, int dst_bytes)
dst[i] = src >> ((3-i) * 8);
}
/* hrawclock is 1/4 the FSB frequency */
static int
intel_hrawclk(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
uint32_t clkcfg;
clkcfg = I915_READ(CLKCFG);
switch (clkcfg & CLKCFG_FSB_MASK) {
case CLKCFG_FSB_400:
return 100;
case CLKCFG_FSB_533:
return 133;
case CLKCFG_FSB_667:
return 166;
case CLKCFG_FSB_800:
return 200;
case CLKCFG_FSB_1067:
return 266;
case CLKCFG_FSB_1333:
return 333;
/* these two are just a guess; one of them might be right */
case CLKCFG_FSB_1600:
case CLKCFG_FSB_1600_ALT:
return 400;
default:
return 133;
}
}
static int
intel_dp_aux_ch(struct intel_output *intel_output,
uint8_t *send, int send_bytes,
@ -169,7 +199,16 @@ intel_dp_aux_ch(struct intel_output *intel_output,
int recv_bytes;
uint32_t ctl;
uint32_t status;
uint32_t aux_clock_divider;
int try;
/* The clock divider is based off the hrawclk,
* and would like to run at 2MHz. So, take the
* hrawclk value and divide by 2 and use that
*/
aux_clock_divider = intel_hrawclk(dev) / 2;
/* Must try at least 3 times according to DP spec */
for (try = 0; try < 5; try++) {
/* Load the send data into the aux channel data registers */
for (i = 0; i < send_bytes; i += 4) {
uint32_t d = pack_aux(send + i, send_bytes - i);;
@ -177,16 +216,12 @@ intel_dp_aux_ch(struct intel_output *intel_output,
I915_WRITE(ch_data + i, d);
}
/* The clock divider is based off the hrawclk,
* and would like to run at 2MHz. The 133 below assumes
* a 266MHz hrawclk; need to figure out how we're supposed
* to know what hrawclk is...
*/
ctl = (DP_AUX_CH_CTL_SEND_BUSY |
DP_AUX_CH_CTL_TIME_OUT_1600us |
DP_AUX_CH_CTL_TIME_OUT_400us |
(send_bytes << DP_AUX_CH_CTL_MESSAGE_SIZE_SHIFT) |
(5 << DP_AUX_CH_CTL_PRECHARGE_2US_SHIFT) |
(133 << DP_AUX_CH_CTL_BIT_CLOCK_2X_SHIFT) |
(aux_clock_divider << DP_AUX_CH_CTL_BIT_CLOCK_2X_SHIFT) |
DP_AUX_CH_CTL_DONE |
DP_AUX_CH_CTL_TIME_OUT_ERROR |
DP_AUX_CH_CTL_RECEIVE_ERROR);
@ -206,6 +241,9 @@ intel_dp_aux_ch(struct intel_output *intel_output,
DP_AUX_CH_CTL_TIME_OUT_ERROR |
DP_AUX_CH_CTL_RECEIVE_ERROR));
(void) I915_READ(ch_ctl);
if ((status & DP_AUX_CH_CTL_TIME_OUT_ERROR) == 0)
break;
}
if ((status & DP_AUX_CH_CTL_DONE) == 0) {
printk(KERN_ERR "dp_aux_ch not done status 0x%08x\n", status);