[RESEND 1/1] drm/i915/dp: Refine TPS4-based HBR3 rejection and add quirk to limit eDP to HBR2
Nautiyal, Ankit K
ankit.k.nautiyal at intel.com
Tue Jul 8 15:13:37 UTC 2025
On 7/8/2025 7:44 PM, Ville Syrjälä wrote:
> On Sun, Jul 06, 2025 at 11:01:49AM +0530, Ankit Nautiyal wrote:
>> Refine the logic introduced in commit 584cf613c24a ("drm/i915/dp: Reject
>> HBR3 when sink doesn't support TPS4") to allow HBR3 on eDP panels that
>> report DPCD revision 1.4, even if TPS4 is not supported. This aligns with
>> the DisplayPort specification, which does not mandate TPS4 support for eDP
>> with DPCD rev 1.4.
>>
>> This change avoids regressions on panels that require HBR3 to operate at
>> their native resolution but do not advertise TPS4 support.
>>
>> Additionally, some ICL/TGL platforms with combo PHY ports suffer from
>> signal integrity issues at HBR3. While certain systems include a
>> Parade PS8461 mux to mitigate this, its presence cannot be reliably
>> detected. Furthermore, broken or missing VBT entries make it unsafe to
>> rely on VBT for enforcing link rate limits.
>>
>> To address the HBR3-related issues on such platforms and eDP panels,
>> introduce a device specific quirk to cap the eDP link rate to HBR2
>> (540000 kHz). This will override any higher advertised rates from
>> the sink or DPCD for specific devices.
>>
>> Currently, the quirk is added for Dell XPS 13 7390 2-in-1 which is
>> reported in gitlab issue #5969 [1].
>>
>> [1] https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/5969
>> [2] https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14517
>>
>> Fixes: 584cf613c24a ("drm/i915/dp: Reject HBR3 when sink doesn't support TPS4")
>> Cc: Jani Nikula <jani.nikula at linux.intel.com>
>> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> Cc: <stable at vger.kernel.org> # v6.15+
>> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/5969
>> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14517
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
>> ---
>> drivers/gpu/drm/i915/display/intel_dp.c | 31 +++++++++++++++++++--
>> drivers/gpu/drm/i915/display/intel_quirks.c | 9 ++++++
>> drivers/gpu/drm/i915/display/intel_quirks.h | 1 +
>> 3 files changed, 39 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index f48912f308df..362e376fca27 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -171,6 +171,15 @@ int intel_dp_link_symbol_clock(int rate)
>> return DIV_ROUND_CLOSEST(rate * 10, intel_dp_link_symbol_size(rate));
>> }
>>
>> +static bool intel_dp_reject_hbr3_due_to_tps4(struct intel_dp *intel_dp)
>> +{
>> + /* TPS4 is not mandatory for eDP with DPCD rev 1.4 */
>> + if (intel_dp_is_edp(intel_dp) && intel_dp->dpcd[DP_DPCD_REV] == 0x14)
>> + return false;
>> +
>> + return !drm_dp_tps4_supported(intel_dp->dpcd);
>> +}
> This feels like it's getty too messy for comfort. I think we should just
> revert the whole thing and quirk that one icl machine.
Alright sure.
Can this be done is same patch, I mean no need for a revert and a
separate quirk patch, right?
Regards,
Ankit
>
>> +
>> static int max_dprx_rate(struct intel_dp *intel_dp)
>> {
>> struct intel_display *display = to_intel_display(intel_dp);
>> @@ -187,13 +196,22 @@ static int max_dprx_rate(struct intel_dp *intel_dp)
>> * HBR3 without TPS4, and are unable to produce a stable
>> * output. Reject HBR3 when TPS4 is not available.
>> */
>> - if (max_rate >= 810000 && !drm_dp_tps4_supported(intel_dp->dpcd)) {
>> + if (max_rate >= 810000 && intel_dp_reject_hbr3_due_to_tps4(intel_dp)) {
>> drm_dbg_kms(display->drm,
>> "[ENCODER:%d:%s] Rejecting HBR3 due to missing TPS4 support\n",
>> encoder->base.base.id, encoder->base.name);
>> max_rate = 540000;
>> }
>>
>> + /*
>> + * Some platforms + eDP panels may not reliably support HBR3
>> + * due to signal integrity limitations, despite advertising it.
>> + * Cap the link rate to HBR2 to avoid unstable configurations for the
>> + * known machines.
>> + */
>> + if (intel_dp_is_edp(intel_dp) && intel_has_quirk(display, QUIRK_EDP_LIMIT_RATE_HBR2))
>> + max_rate = min(max_rate, 540000);
>> +
>> return max_rate;
>> }
>>
>> @@ -4304,13 +4322,22 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp)
>> * HBR3 without TPS4, and are unable to produce a stable
>> * output. Reject HBR3 when TPS4 is not available.
>> */
>> - if (rate >= 810000 && !drm_dp_tps4_supported(intel_dp->dpcd)) {
>> + if (rate >= 810000 && intel_dp_reject_hbr3_due_to_tps4(intel_dp)) {
>> drm_dbg_kms(display->drm,
>> "[ENCODER:%d:%s] Rejecting HBR3 due to missing TPS4 support\n",
>> encoder->base.base.id, encoder->base.name);
>> break;
>> }
>>
>> + /*
>> + * Some platforms cannot reliably drive HBR3 rates due to PHY limitations,
>> + * even if the sink advertises support. Reject any sink rates above HBR2 on
>> + * the known machines for stable output.
>> + */
>> + if (rate >= 810000 &&
>> + intel_has_quirk(display, QUIRK_EDP_LIMIT_RATE_HBR2))
>> + break;
>> +
>> intel_dp->sink_rates[i] = rate;
>> }
>> intel_dp->num_sink_rates = i;
>> diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c b/drivers/gpu/drm/i915/display/intel_quirks.c
>> index a32fae510ed2..d2e16b79d6be 100644
>> --- a/drivers/gpu/drm/i915/display/intel_quirks.c
>> +++ b/drivers/gpu/drm/i915/display/intel_quirks.c
>> @@ -80,6 +80,12 @@ static void quirk_fw_sync_len(struct intel_dp *intel_dp)
>> drm_info(display->drm, "Applying Fast Wake sync pulse count quirk\n");
>> }
>>
>> +static void quirk_edp_limit_rate_hbr2(struct intel_display *display)
>> +{
>> + intel_set_quirk(display, QUIRK_EDP_LIMIT_RATE_HBR2);
>> + drm_info(display->drm, "Applying eDP Limit rate to HBR2 quirk\n");
>> +}
>> +
>> struct intel_quirk {
>> int device;
>> int subsystem_vendor;
>> @@ -231,6 +237,9 @@ static struct intel_quirk intel_quirks[] = {
>> { 0x3184, 0x1019, 0xa94d, quirk_increase_ddi_disabled_time },
>> /* HP Notebook - 14-r206nv */
>> { 0x0f31, 0x103c, 0x220f, quirk_invert_brightness },
>> +
>> + /* Dell XPS 13 7390 2-in-1 */
>> + { 0x8a12, 0x1028, 0x08b0, quirk_edp_limit_rate_hbr2 },
>> };
>>
>> static const struct intel_dpcd_quirk intel_dpcd_quirks[] = {
>> diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h b/drivers/gpu/drm/i915/display/intel_quirks.h
>> index cafdebda7535..06da0e286c67 100644
>> --- a/drivers/gpu/drm/i915/display/intel_quirks.h
>> +++ b/drivers/gpu/drm/i915/display/intel_quirks.h
>> @@ -20,6 +20,7 @@ enum intel_quirk_id {
>> QUIRK_LVDS_SSC_DISABLE,
>> QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
>> QUIRK_FW_SYNC_LEN,
>> + QUIRK_EDP_LIMIT_RATE_HBR2,
>> };
>>
>> void intel_init_quirks(struct intel_display *display);
>> --
>> 2.45.2
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