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drm/tegra: dpaux: Retry on transfer size mismatch 

When a transfer didn't complete transmission of the requested number of
bytes, signal that the transaction should be retried.

Signed-off-by: Thierry Reding <treding@nvidia.com>
This commit is contained in:
Thierry Reding 2016-03-03 15:32:13 +01:00
parent 5e881f6b29
commit 245ce70cd4
1 changed files with 18 additions and 7 deletions
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25
drivers/gpu/drm/tegra/dpaux.c
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@ -121,6 +121,7 @@ static ssize_t tegra_dpaux_transfer(struct drm_dp_aux *aux,
struct tegra_dpaux *dpaux = to_dpaux(aux);
unsigned long status;
ssize_t ret = 0;
u8 reply = 0;
u32 value;
/* Tegra has 4x4 byte DP AUX transmit and receive FIFOs. */
@ -215,23 +216,23 @@ static ssize_t tegra_dpaux_transfer(struct drm_dp_aux *aux,
switch ((value & DPAUX_DP_AUXSTAT_REPLY_TYPE_MASK) >> 16) {
case 0x00:
msg->reply = DP_AUX_NATIVE_REPLY_ACK;
reply = DP_AUX_NATIVE_REPLY_ACK;
break;
case 0x01:
msg->reply = DP_AUX_NATIVE_REPLY_NACK;
reply = DP_AUX_NATIVE_REPLY_NACK;
break;
case 0x02:
msg->reply = DP_AUX_NATIVE_REPLY_DEFER;
reply = DP_AUX_NATIVE_REPLY_DEFER;
break;
case 0x04:
msg->reply = DP_AUX_I2C_REPLY_NACK;
reply = DP_AUX_I2C_REPLY_NACK;
break;
case 0x08:
msg->reply = DP_AUX_I2C_REPLY_DEFER;
reply = DP_AUX_I2C_REPLY_DEFER;
break;
}
@ -239,14 +240,24 @@ static ssize_t tegra_dpaux_transfer(struct drm_dp_aux *aux,
if (msg->request & DP_AUX_I2C_READ) {
size_t count = value & DPAUX_DP_AUXSTAT_REPLY_MASK;
if (WARN_ON(count != msg->size))
count = min_t(size_t, count, msg->size);
/*
* There might be a smarter way to do this, but since
* the DP helpers will already retry transactions for
* an -EBUSY return value, simply reuse that instead.
*/
if (count != msg->size) {
ret = -EBUSY;
goto out;
}
tegra_dpaux_read_fifo(dpaux, msg->buffer, count);
ret = count;
}
}
msg->reply = reply;
out:
return ret;
}