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drm/i915/dp: Really try 5 times before giving up.

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Only stop trying if the aux channel sucessfully reports that the
transmission was completed, otherwise try again. On the 5th failure,
bail and report that something is amiss.

This fixes a sporadic failure in reading the EDID for my external panel
over DP.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org
This commit is contained in:
Chris Wilson 2010-08-18 18:12:56 +01:00
parent b66d842467
commit 4f7f7b7eb9
1 changed files with 28 additions and 30 deletions
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58
drivers/gpu/drm/i915/intel_dp.c
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@ -239,7 +239,6 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
uint32_t ch_data = ch_ctl + 4;
int i;
int recv_bytes;
uint32_t ctl;
uint32_t status;
uint32_t aux_clock_divider;
int try, precharge;
@ -263,41 +262,43 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
else
precharge = 5;
if (I915_READ(ch_ctl) & DP_AUX_CH_CTL_SEND_BUSY) {
DRM_ERROR("dp_aux_ch not started status 0x%08x\n",
I915_READ(ch_ctl));
return -EBUSY;
}
/* 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);
I915_WRITE(ch_data + i, d);
}
ctl = (DP_AUX_CH_CTL_SEND_BUSY |
DP_AUX_CH_CTL_TIME_OUT_400us |
(send_bytes << DP_AUX_CH_CTL_MESSAGE_SIZE_SHIFT) |
(precharge << DP_AUX_CH_CTL_PRECHARGE_2US_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);
for (i = 0; i < send_bytes; i += 4)
I915_WRITE(ch_data + i,
pack_aux(send + i, send_bytes - i));
/* Send the command and wait for it to complete */
I915_WRITE(ch_ctl, ctl);
(void) I915_READ(ch_ctl);
I915_WRITE(ch_ctl,
DP_AUX_CH_CTL_SEND_BUSY |
DP_AUX_CH_CTL_TIME_OUT_400us |
(send_bytes << DP_AUX_CH_CTL_MESSAGE_SIZE_SHIFT) |
(precharge << DP_AUX_CH_CTL_PRECHARGE_2US_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);
for (;;) {
udelay(100);
status = I915_READ(ch_ctl);
if ((status & DP_AUX_CH_CTL_SEND_BUSY) == 0)
break;
udelay(100);
}
/* Clear done status and any errors */
I915_WRITE(ch_ctl, (status |
DP_AUX_CH_CTL_DONE |
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)
I915_WRITE(ch_ctl,
status |
DP_AUX_CH_CTL_DONE |
DP_AUX_CH_CTL_TIME_OUT_ERROR |
DP_AUX_CH_CTL_RECEIVE_ERROR);
if (status & DP_AUX_CH_CTL_DONE)
break;
}
@ -324,15 +325,12 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
/* Unload any bytes sent back from the other side */
recv_bytes = ((status & DP_AUX_CH_CTL_MESSAGE_SIZE_MASK) >>
DP_AUX_CH_CTL_MESSAGE_SIZE_SHIFT);
if (recv_bytes > recv_size)
recv_bytes = recv_size;
for (i = 0; i < recv_bytes; i += 4) {
uint32_t d = I915_READ(ch_data + i);
unpack_aux(d, recv + i, recv_bytes - i);
}
for (i = 0; i < recv_bytes; i += 4)
unpack_aux(I915_READ(ch_data + i),
recv + i, recv_bytes - i);
return recv_bytes;
}