On Thu, Jul 28, 2016 at 05:54:42PM +0300, ville.syrjala@xxxxxxxxxxxxxxx wrote:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> Restore the correct behaviour (as in check msg.reply) when aux
> ->transfer() returns 0. It got removed in
> commit 82922da39190 ("drm/dp_helper: Retry aux transactions on all errors")
>
> Now I can actually dump the "entire" DPCD on a Dell UP2314Q with
> ddrescue. It has some offsets in the DPCD that can't be read
> for some resaon, all you get is defers. Previously ddrescue would
> just give up at the first unredable offset on account of
> read() returning 0 means EOF. Here's the ddrescue log
> for the interested:
> 0x00000000 0x00001400 +
> 0x00001400 0x00000030 -
> 0x00001430 0x000001D0 +
> 0x00001600 0x00000030 -
> 0x00001630 0x0001F9D0 +
> 0x00021000 0x00000001 -
> 0x00021001 0x000DEFFF +
>
> Cc: Lyude <cpaul@xxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 82922da39190 ("drm/dp_helper: Retry aux transactions on all errors")
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Seems to correctly restore that special case.
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Dave, since I just send out a drm-misc pull, can you pls apply this one
directly to drm-next?
-Daniel
> ---
> drivers/gpu/drm/drm_dp_helper.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 091053e995e5..8f11b8741e42 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -203,7 +203,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
>
> ret = aux->transfer(aux, &msg);
>
> - if (ret > 0) {
> + if (ret >= 0) {
> native_reply = msg.reply & DP_AUX_NATIVE_REPLY_MASK;
> if (native_reply == DP_AUX_NATIVE_REPLY_ACK) {
> if (ret == size)
> --
> 2.7.4
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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