Re: [PATCH v5 4/4] drm/dp: Revert "drm/dp: Introduce EDID-based quirks"

Jani Nikula
2021-01-11T19:08:55Z

On Thu, 07 Jan 2021, Lyude Paul <lyude@redhat.com> wrote:
> This reverts commit 0883ce8146ed6074c76399f4e70dbed788582e12. Originally
> these quirks were added because of the issues with using the eDP
> backlight interfaces on certain laptop panels, which made it impossible
> to properly probe for DPCD backlight support without having a whitelist
> for panels that we know have working VESA backlight control interfaces
> over DPCD. As well, it should be noted it was impossible to use the
> normal sink OUI for recognizing these panels as none of them actually
> filled out their OUIs, hence needing to resort to checking EDIDs.
>
> At the time we weren't really sure why certain panels had issues with
> DPCD backlight controls, but we eventually figured out that there was a
> second interface that these problematic laptop panels actually did work
> with and advertise properly: Intel's proprietary backlight interface for
> HDR panels. So far the testing we've done hasn't brought any panels to
> light that advertise this interface and don't support it properly, which
> means we finally have a real solution to this problem.
>
> As a result, we now have no need for the force DPCD backlight quirk, and
> furthermore this also removes the need for any kind of EDID quirk
> checking in DRM. So, let's just revert it for now since we were the only
> driver using this.
>
> v3:
> * Rebase
> v2:
> * Fix indenting error picked up by checkpatch in
> intel_edp_init_connector()
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Acked-by: Jani Nikula <jani.nikula@intel.com>

Still stands.

BR,
Jani.

> Cc: thaytan@noraisin.net
> Cc: Vasily Khoruzhick <anarsoul@gmail.com>
> ---
> drivers/gpu/drm/drm_dp_helper.c | 83 +------------------
> drivers/gpu/drm/drm_dp_mst_topology.c | 3 +-
> .../drm/i915/display/intel_display_types.h | 1 -
> drivers/gpu/drm/i915/display/intel_dp.c | 9 +-
> drivers/gpu/drm/i915/display/intel_dp_mst.c | 3 +-
> drivers/gpu/drm/i915/display/intel_psr.c | 2 +-
> include/drm/drm_dp_helper.h | 21 +----
> 7 files changed, 9 insertions(+), 113 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 3ecde451f523..19dbdeb581cb 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -1236,7 +1236,7 @@ bool drm_dp_read_sink_count_cap(struct drm_connector *connector,
> return connector->connector_type != DRM_MODE_CONNECTOR_eDP &&
> dpcd[DP_DPCD_REV] >= DP_DPCD_REV_11 &&
> dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT &&
> - !drm_dp_has_quirk(desc, 0, DP_DPCD_QUIRK_NO_SINK_COUNT);
> + !drm_dp_has_quirk(desc, DP_DPCD_QUIRK_NO_SINK_COUNT);
> }
> EXPORT_SYMBOL(drm_dp_read_sink_count_cap);
>
> @@ -1957,87 +1957,6 @@ drm_dp_get_quirks(const struct drm_dp_dpcd_ident *ident, bool is_branch)
> #undef DEVICE_ID_ANY
> #undef DEVICE_ID
>
> -struct edid_quirk {
> - u8 mfg_id[2];
> - u8 prod_id[2];
> - u32 quirks;
> -};
> -
> -#define MFG(first, second) { (first), (second) }
> -#define PROD_ID(first, second) { (first), (second) }
> -
> -/*
> - * Some devices have unreliable OUIDs where they don't set the device ID
> - * correctly, and as a result we need to use the EDID for finding additional
> - * DP quirks in such cases.
> - */
> -static const struct edid_quirk edid_quirk_list[] = {
> - /* Optional 4K AMOLED panel in the ThinkPad X1 Extreme 2nd Generation
> - * only supports DPCD backlight controls
> - */
> - { MFG(0x4c, 0x83), PROD_ID(0x41, 0x41), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
> - /*
> - * Some Dell CML 2020 systems have panels support both AUX and PWM
> - * backlight control, and some only support AUX backlight control. All
> - * said panels start up in AUX mode by default, and we don't have any
> - * support for disabling HDR mode on these panels which would be
> - * required to switch to PWM backlight control mode (plus, I'm not
> - * even sure we want PWM backlight controls over DPCD backlight
> - * controls anyway...). Until we have a better way of detecting these,
> - * force DPCD backlight mode on all of them.
> - */
> - { MFG(0x06, 0xaf), PROD_ID(0x9b, 0x32), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
> - { MFG(0x06, 0xaf), PROD_ID(0xeb, 0x41), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
> - { MFG(0x4d, 0x10), PROD_ID(0xc7, 0x14), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
> - { MFG(0x4d, 0x10), PROD_ID(0xe6, 0x14), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
> - { MFG(0x4c, 0x83), PROD_ID(0x47, 0x41), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
> - { MFG(0x09, 0xe5), PROD_ID(0xde, 0x08), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
> -};
> -
> -#undef MFG
> -#undef PROD_ID
> -
> -/**
> - * drm_dp_get_edid_quirks() - Check the EDID of a DP device to find additional
> - * DP-specific quirks
> - * @edid: The EDID to check
> - *
> - * While OUIDs are meant to be used to recognize a DisplayPort device, a lot
> - * of manufacturers don't seem to like following standards and neglect to fill
> - * the dev-ID in, making it impossible to only use OUIDs for determining
> - * quirks in some cases. This function can be used to check the EDID and look
> - * up any additional DP quirks. The bits returned by this function correspond
> - * to the quirk bits in &drm_dp_quirk.
> - *
> - * Returns: a bitmask of quirks, if any. The driver can check this using
> - * drm_dp_has_quirk().
> - */
> -u32 drm_dp_get_edid_quirks(const struct edid *edid)
> -{
> - const struct edid_quirk *quirk;
> - u32 quirks = 0;
> - int i;
> -
> - if (!edid)
> - return 0;
> -
> - for (i = 0; i < ARRAY_SIZE(edid_quirk_list); i++) {
> - quirk = &edid_quirk_list[i];
> - if (memcmp(quirk->mfg_id, edid->mfg_id,
> - sizeof(edid->mfg_id)) == 0 &&
> - memcmp(quirk->prod_id, edid->prod_code,
> - sizeof(edid->prod_code)) == 0)
> - quirks |= quirk->quirks;
> - }
> -
> - DRM_DEBUG_KMS("DP sink: EDID mfg %*phD prod-ID %*phD quirks: 0x%04x\n",
> - (int)sizeof(edid->mfg_id), edid->mfg_id,
> - (int)sizeof(edid->prod_code), edid->prod_code, quirks);
> -
> - return quirks;
> -}
> -EXPORT_SYMBOL(drm_dp_get_edid_quirks);
> -
> /**
> * drm_dp_read_desc - read sink/branch descriptor from DPCD
> * @aux: DisplayPort AUX channel
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 0401b2f47500..a2e692a0c6c2 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -5824,8 +5824,7 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
> if (drm_dp_read_desc(port->mgr->aux, &desc, true))
> return NULL;
>
> - if (drm_dp_has_quirk(&desc, 0,
> - DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) &&
> + if (drm_dp_has_quirk(&desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) &&
> port->mgr->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14 &&
> port->parent == port->mgr->mst_primary) {
> u8 downstreamport;
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index b24d80ffd18b..744bdf39a7b1 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1390,7 +1390,6 @@ struct intel_dp {
> int max_link_rate;
> /* sink or branch descriptor */
> struct drm_dp_desc desc;
> - u32 edid_quirks;
> struct drm_dp_aux aux;
> u32 aux_busy_last_status;
> u8 train_set[4];
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 8a00e609085f..7fcb8ca10f96 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -162,8 +162,7 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
> int i, max_rate;
> int max_lttpr_rate;
>
> - if (drm_dp_has_quirk(&intel_dp->desc, 0,
> - DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS)) {
> + if (drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS)) {
> /* Needed, e.g., for Apple MBP 2017, 15 inch eDP Retina panel */
> static const int quirk_rates[] = { 162000, 270000, 324000 };
>
> @@ -2823,8 +2822,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> struct intel_connector *intel_connector = intel_dp->attached_connector;
> struct intel_digital_connector_state *intel_conn_state =
> to_intel_digital_connector_state(conn_state);
> - bool constant_n = drm_dp_has_quirk(&intel_dp->desc, 0,
> - DP_DPCD_QUIRK_CONSTANT_N);
> + bool constant_n = drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_CONSTANT_N);
> int ret = 0, output_bpp;
>
> if (HAS_PCH_SPLIT(dev_priv) && !HAS_DDI(dev_priv) && port != PORT_A)
> @@ -7007,7 +7005,6 @@ intel_dp_set_edid(struct intel_dp *intel_dp)
> }
>
> drm_dp_cec_set_edid(&intel_dp->aux, edid);
> - intel_dp->edid_quirks = drm_dp_get_edid_quirks(edid);
> }
>
> static void
> @@ -7021,7 +7018,6 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
>
> intel_dp->has_hdmi_sink = false;
> intel_dp->has_audio = false;
> - intel_dp->edid_quirks = 0;
>
> intel_dp->dfp.max_bpc = 0;
> intel_dp->dfp.max_dotclock = 0;
> @@ -8425,7 +8421,6 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> if (edid) {
> if (drm_add_edid_modes(connector, edid)) {
> drm_connector_update_edid_property(connector, edid);
> - intel_dp->edid_quirks = drm_dp_get_edid_quirks(edid);
> } else {
> kfree(edid);
> edid = ERR_PTR(-EINVAL);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 27f04aed8764..3e7bbf8d6620 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -53,8 +53,7 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
> struct drm_i915_private *i915 = to_i915(connector->base.dev);
> const struct drm_display_mode *adjusted_mode =
> &crtc_state->hw.adjusted_mode;
> - bool constant_n = drm_dp_has_quirk(&intel_dp->desc, 0,
> - DP_DPCD_QUIRK_CONSTANT_N);
> + bool constant_n = drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_CONSTANT_N);
> int bpp, slots = -EINVAL;
>
> crtc_state->lane_count = limits->max_lane_count;
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index c24ae69426cf..1e6c1fa59d4a 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -305,7 +305,7 @@ void intel_psr_init_dpcd(struct intel_dp *intel_dp)
> drm_dbg_kms(&dev_priv->drm, "eDP panel supports PSR version %x\n",
> intel_dp->psr_dpcd[0]);
>
> - if (drm_dp_has_quirk(&intel_dp->desc, 0, DP_DPCD_QUIRK_NO_PSR)) {
> + if (drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_NO_PSR)) {
> drm_dbg_kms(&dev_priv->drm,
> "PSR support not currently available for this panel\n");
> return;
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 6236f212da61..edffd1dcca3e 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -2029,16 +2029,13 @@ struct drm_dp_desc {
>
> int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
> bool is_branch);
> -u32 drm_dp_get_edid_quirks(const struct edid *edid);
>
> /**
> * enum drm_dp_quirk - Display Port sink/branch device specific quirks
> *
> * Display Port sink and branch devices in the wild have a variety of bugs, try
> * to collect them here. The quirks are shared, but it's up to the drivers to
> - * implement workarounds for them. Note that because some devices have
> - * unreliable OUIDs, the EDID of sinks should also be checked for quirks using
> - * drm_dp_get_edid_quirks().
> + * implement workarounds for them.
> */
> enum drm_dp_quirk {
> /**
> @@ -2070,16 +2067,6 @@ enum drm_dp_quirk {
> * The DSC caps can be read from the physical aux instead.
> */
> DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD,
> - /**
> - * @DP_QUIRK_FORCE_DPCD_BACKLIGHT:
> - *
> - * The device is telling the truth when it says that it uses DPCD
> - * backlight controls, even if the system's firmware disagrees. This
> - * quirk should be checked against both the ident and panel EDID.
> - * When present, the driver should honor the DPCD backlight
> - * capabilities advertised.
> - */
> - DP_QUIRK_FORCE_DPCD_BACKLIGHT,
> /**
> * @DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS:
> *
> @@ -2092,16 +2079,14 @@ enum drm_dp_quirk {
> /**
> * drm_dp_has_quirk() - does the DP device have a specific quirk
> * @desc: Device descriptor filled by drm_dp_read_desc()
> - * @edid_quirks: Optional quirk bitmask filled by drm_dp_get_edid_quirks()
> * @quirk: Quirk to query for
> *
> * Return true if DP device identified by @desc has @quirk.
> */
> static inline bool
> -drm_dp_has_quirk(const struct drm_dp_desc *desc, u32 edid_quirks,
> - enum drm_dp_quirk quirk)
> +drm_dp_has_quirk(const struct drm_dp_desc *desc, enum drm_dp_quirk quirk)
> {
> - return (desc->quirks | edid_quirks) & BIT(quirk);
> + return desc->quirks & BIT(quirk);
> }
>
> #ifdef CONFIG_DRM_DP_CEC