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 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. Signed-off-by: Matt Atwood <matthew.s.atwood@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); + + 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 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx