On Fri, Oct 16, 2015 at 2:54 PM, Rob Clark <robdclark@xxxxxxxxx> wrote:
> 1) don't let other threads trying to bang on aux channel interrupt the
> defer timeout/logic
> 2) don't let other threads interrupt the i2c over aux logic
>
> ---
> This wasn't actually fixing things w/ problematic monitor, but seems
> like generally a good idea. At least AFAIU you shouldn't allow the
> sequence of transfers for i2c over aux be interrupted but unrelated
> chatter.
So, I got confirmation today that this patch actually does fix things
w/ a different problematic Dell monitor. So I think it actually is
the right thing to do.
BR,
-R
> This applies on top of the DPCD logging patch.
>
> drivers/gpu/drm/drm_dp_helper.c | 27 +++++++++++++++++----------
> 1 file changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index ccb1f8a..e409b5f 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -163,8 +163,6 @@ static ssize_t aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> {
> ssize_t ret;
>
> - mutex_lock(&aux->hw_mutex);
> -
> DRM_DEBUG_DPCD("%s: req=0x%02x, address=0x%05x, size=%zu\n", aux->name,
> msg->request, msg->address, msg->size);
>
> @@ -196,8 +194,6 @@ static ssize_t aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> }
> }
>
> - mutex_unlock(&aux->hw_mutex);
> -
> return ret;
> }
>
> @@ -220,7 +216,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
> {
> struct drm_dp_aux_msg msg;
> unsigned int retry;
> - int err;
> + int err = 0;
>
> memset(&msg, 0, sizeof(msg));
> msg.address = offset;
> @@ -228,6 +224,8 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
> msg.buffer = buffer;
> msg.size = size;
>
> + mutex_lock(&aux->hw_mutex);
> +
> /*
> * The specification doesn't give any recommendation on how often to
> * retry native transactions. We used to retry 7 times like for
> @@ -241,18 +239,19 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
> if (err == -EBUSY)
> continue;
>
> - return err;
> + goto unlock;
> }
>
> switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
> case DP_AUX_NATIVE_REPLY_ACK:
> if (err < size)
> - return -EPROTO;
> - return err;
> + err = -EPROTO;
> + goto unlock;
>
> case DP_AUX_NATIVE_REPLY_NACK:
> DRM_DEBUG_DPCD("native nack (result=%d, size=%zu)\n", err, msg.size);
> - return -EIO;
> + err = -EIO;
> + goto unlock;
>
> case DP_AUX_NATIVE_REPLY_DEFER:
> DRM_DEBUG_DPCD("native defer\n");
> @@ -262,7 +261,11 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
> }
>
> DRM_ERROR("DPCD: too many retries, giving up!\n");
> - return -EIO;
> + err = -EIO;
> +
> +unlock:
> + mutex_unlock(&aux->hw_mutex);
> + return err;
> }
>
> /**
> @@ -698,6 +701,8 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
>
> memset(&msg, 0, sizeof(msg));
>
> + mutex_lock(&aux->hw_mutex);
> +
> for (i = 0; i < num; i++) {
> msg.address = msgs[i].addr;
> msg.request = (msgs[i].flags & I2C_M_RD) ?
> @@ -741,6 +746,8 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
> msg.size = 0;
> (void)drm_dp_i2c_do_msg(aux, &msg);
>
> + mutex_unlock(&aux->hw_mutex);
> +
> return err;
> }
>
> --
> 2.5.0
>
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