On Tue, 2018-03-06 at 15:24 -0800, Rodrigo Vivi wrote:
> On Tue, Mar 06, 2018 at 10:37:48AM -0800, matthew.s.atwood@xxxxxxxxx wrote:
> > From: Matt Atwood <matthew.s.atwood@xxxxxxxxx>
> >
> > DP_TRAINING_AUX_RD_INTERVAL with DP 1.3 spec changed bit scheme from 8
> > bits to 7 bits in DPCD 0x000e. The 8th bit describes a new feature, for
> > panels that use this new feature, this would cause a wait interval for
> > clock recovery of at least 512 ms, much higher then spec maximum of 16 ms.
> > This behavior is described in table 2-158 of DP 1.4 spec address 0000Eh.
> > To avoid breaking panels
See comment below:
> that are not spec compliant we now warn on
> > invalid values.
> >
> > V2: commit title/message, masking all 7 bits, warn on out of spec values.
>
> this approach is even better imho.
>
> >
> > Signed-off-by: Matt Atwood <matthew.s.atwood@xxxxxxxxx>
>
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
>
> > ---
> > drivers/gpu/drm/drm_dp_helper.c | 18 ++++++++++++++----
> > include/drm/drm_dp_helper.h | 1 +
> > 2 files changed, 15 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> > index adf79be..a718ccc 100644
> > --- a/drivers/gpu/drm/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/drm_dp_helper.c
> > @@ -119,18 +119,28 @@ u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SI
> > EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
> >
> > void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
> > - if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
> > + int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] & DP_TRAINING_AUX_RD_MASK;
> > +
> > + if (rd_interval > 4)
> > + DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)", rd_interval);
Some default for panels without a valid value?
rd_interval = 4;
"AUX read interval out of range, using max %d ms"
> > +
> > + if (rd_interval == 0)
> > udelay(100);
> > else
> > - mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
> > + mdelay(rd_interval * 4);
> > }
> > EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
> >
> > void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
> > - if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
> > + int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] & DP_TRAINING_AUX_RD_MASK;
> > +
> > + if (rd_interval > 4)
> > + DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)", rd_interval);
> > +
> > + if (rd_interval == 0)
> > udelay(400);
> > else
> > - mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
> > + mdelay(rd_interval * 4);
> > }
> > EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
> >
> > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> > index da58a42..f80acf1 100644
> > --- a/include/drm/drm_dp_helper.h
> > +++ b/include/drm/drm_dp_helper.h
> > @@ -118,6 +118,7 @@
> > # define DP_DPCD_DISPLAY_CONTROL_CAPABLE (1 << 3) /* edp v1.2 or higher */
> >
> > #define DP_TRAINING_AUX_RD_INTERVAL 0x00e /* XXX 1.2? */
> > +# define DP_TRAINING_AUX_RD_MASK 0x7F /* 1.3 */
> >
> > #define DP_ADAPTER_CAP 0x00f /* 1.2 */
> > # define DP_FORCE_LOAD_SENSE_CAP (1 << 0)
> > --
> > 2.7.4
> >
> > _______________________________________________
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> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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