On Thu, Mar 18, 2021 at 08:00:10PM +0200, Ville Syrjälä wrote:
On Wed, Mar 17, 2021 at 08:49:01PM +0200, Imre Deak wrote:
By the specification the 0xF0000 - 0xF02FF range is only valid if the LTTPR revision at 0xF0000 is at least 1.4. Disable the LTTPR support otherwise.
Fixes: 7b2a4ab8b0ef ("drm/i915: Switch to LTTPR transparent mode link training") Cc: stable@vger.kernel.org # v5.11 Cc: Ville Syrjälä ville.syrjala@linux.intel.com Signed-off-by: Imre Deak imre.deak@intel.com
.../gpu/drm/i915/display/intel_dp_link_training.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c index d8d90903226f..d92eb192c89d 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -100,17 +100,23 @@ static bool intel_dp_read_lttpr_common_caps(struct intel_dp *intel_dp) return false; if (drm_dp_read_lttpr_common_caps(&intel_dp->aux,
intel_dp->lttpr_common_caps) < 0) {intel_dp_reset_lttpr_common_caps(intel_dp);return false;- }
intel_dp->lttpr_common_caps) < 0)goto reset_caps;BTW just noticed this oddball thing in the spec: "DPTX shall read specific registers within the LTTPR field (DPCD Addresses F0000h through F0004h; see Table 2-198) to determine whether any LTTPR(s) are present and if so, how many. This read shall be in the form of a 5-byte native AUX Read transaction."
Why exactly 5 bytes? I have no idea. Doesn't really make sense. Just wondering if we really need to respect that and some LTTPRs would fsck things up if we read more...
I pointed this out to spec people and the new version (2.1) will require this to be 8 bytes. But yes, I do hope no existing ones depend on this being 5 bytes.
Anyways Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com
drm_dbg_kms(&dp_to_i915(intel_dp)->drm, "LTTPR common capabilities: %*ph\n", (int)sizeof(intel_dp->lttpr_common_caps), intel_dp->lttpr_common_caps);
- /* The minimum value of LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV is 1.4 */
- if (intel_dp->lttpr_common_caps[0] < 0x14)
goto reset_caps;- return true;
+reset_caps:
- intel_dp_reset_lttpr_common_caps(intel_dp);
- return false;
} static bool -- 2.25.1
-- Ville Syrjälä Intel