Max backlight value for the panel was being calculated using byte count i.e. 0xffff if 2 bytes are supported for backlight brightness and 0xff if 1 byte is supported. However, EDP_PWMGEN_BIT_COUNT determines the number of active control bits used for the brightness setting. Thus, even if the panel uses 2 byte setting, it might not use all the control bits. Thus, max backlight should be set based on the value of EDP_PWMGEN_BIT_COUNT instead of assuming 65535 or 255. Additionally, EDP_PWMGEN_BIT_COUNT was being updated based on the VBT frequency which results in a different max backlight value. Thus, setting of EDP_PWMGEN_BIT_COUNT is moved to setup phase instead of enable so that max backlight can be calculated correctly. Only the frequency divider is set during the enable phase using the value of EDP_PWMGEN_BIT_COUNT. This is based off the original patch series from Furquan Shaikh <furquan(a)google.com&gt;: https://patchwork.freedesktop.org/patch/317255/?series=62326&rev=3 Changes since original patch: * Remove unused intel_dp variable in intel_dp_aux_setup_backlight() * Fix checkpatch issues * Make sure that we rewrite the pwmgen bit count whenever we bring the panel out of D3 mode v2 by Jani: * rebase * fix readb return value check Cc: Furquan Shaikh <furquan(a)google.com&gt; Tested-by: AceLan Kao <acelan.kao(a)canonical.com&gt; Tested-by: Perry Yuan <pyuan(a)redhat.com&gt; Signed-off-by: Lyude Paul <lyude(a)redhat.com&gt; Signed-off-by: Jani Nikula <jani.nikula(a)intel.com&gt; Link: https://patchwork.freedesktop.org/patch/msgid/20200116211623.53799-2-lyud... --- .../drm/i915/display/intel_display_types.h | 3 + .../drm/i915/display/intel_dp_aux_backlight.c | 139 ++++++++++++------ 2 files changed, 95 insertions(+), 47 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h index 888ea8a170d1..778bd30743e5 100644 --- a/drivers/gpu/drm/i915/display/intel_display_types.h +++ b/drivers/gpu/drm/i915/display/intel_display_types.h @@ -214,6 +214,9 @@ struct intel_panel { u8 controller; /* bxt+ only */ struct pwm_device *pwm; + /* DPCD backlight */ + u8 pwmgen_bit_count; + struct backlight_device *device; /* Connector and platform specific backlight functions */ diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 7c653f8c307f..345eed641455 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -111,61 +111,28 @@ static bool intel_dp_aux_set_pwm_freq(struct intel_connector *connector) { struct drm_i915_private *dev_priv = to_i915(connector->base.dev); struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder); - int freq, fxp, fxp_min, fxp_max, fxp_actual, f = 1; - u8 pn, pn_min, pn_max; + const u8 pn = connector->panel.backlight.pwmgen_bit_count; + int freq, fxp, f, fxp_actual, fxp_min, fxp_max; - /* Find desired value of (F x P) - * Note that, if F x P is out of supported range, the maximum value or - * minimum value will applied automatically. So no need to check that. - */ freq = dev_priv->vbt.backlight.pwm_freq_hz; - DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz\n", freq); if (!freq) { DRM_DEBUG_KMS("Use panel default backlight frequency\n"); return false; } fxp = DIV_ROUND_CLOSEST(KHz(DP_EDP_BACKLIGHT_FREQ_BASE_KHZ), freq); + f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255); + fxp_actual = f << pn; - /* Use highest possible value of Pn for more granularity of brightness - * adjustment while satifying the conditions below. - * - Pn is in the range of Pn_min and Pn_max - * - F is in the range of 1 and 255 - * - FxP is within 25% of desired value. - * Note: 25% is arbitrary value and may need some tweak. - */ - if (drm_dp_dpcd_readb(&intel_dp->aux, - DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min) != 1) { - DRM_DEBUG_KMS("Failed to read pwmgen bit count cap min\n"); - return false; - } - if (drm_dp_dpcd_readb(&intel_dp->aux, - DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max) != 1) { - DRM_DEBUG_KMS("Failed to read pwmgen bit count cap max\n"); - return false; - } - pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK; - pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK; - + /* Ensure frequency is within 25% of desired value */ fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4); fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4); - if (fxp_min < (1 << pn_min) || (255 << pn_max) < fxp_max) { - DRM_DEBUG_KMS("VBT defined backlight frequency out of range\n"); - return false; - } - for (pn = pn_max; pn >= pn_min; pn--) { - f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255); - fxp_actual = f << pn; - if (fxp_min <= fxp_actual && fxp_actual <= fxp_max) - break; - } - - if (drm_dp_dpcd_writeb(&intel_dp->aux, - DP_EDP_PWMGEN_BIT_COUNT, pn) < 0) { - DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n"); + if (fxp_min > fxp_actual || fxp_actual > fxp_max) { + DRM_DEBUG_KMS("Actual frequency out of range\n"); return false; } + if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_BACKLIGHT_FREQ_SET, (u8) f) < 0) { DRM_DEBUG_KMS("Failed to write aux backlight freq\n"); @@ -179,6 +146,7 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st { struct intel_connector *connector = to_intel_connector(conn_state->connector); struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder); + struct intel_panel *panel = &connector->panel; u8 dpcd_buf, new_dpcd_buf, edp_backlight_mode; if (drm_dp_dpcd_readb(&intel_dp->aux, @@ -197,6 +165,12 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st case DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT: new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK; new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD; + + if (drm_dp_dpcd_writeb(&intel_dp->aux, + DP_EDP_PWMGEN_BIT_COUNT, + panel->backlight.pwmgen_bit_count) < 0) + DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n"); + break; /* Do nothing when it is already DPCD mode */ @@ -226,20 +200,91 @@ static void intel_dp_aux_disable_backlight(const struct drm_connector_state *old false); } +static u32 intel_dp_aux_calc_max_backlight(struct intel_connector *connector) +{ + struct drm_i915_private *i915 = to_i915(connector->base.dev); + struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder); + struct intel_panel *panel = &connector->panel; + u32 max_backlight = 0; + int freq, fxp, fxp_min, fxp_max, fxp_actual, f = 1; + u8 pn, pn_min, pn_max; + + if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT, &pn) == 1) { + pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK; + max_backlight = (1 << pn) - 1; + } + + /* Find desired value of (F x P) + * Note that, if F x P is out of supported range, the maximum value or + * minimum value will applied automatically. So no need to check that. + */ + freq = i915->vbt.backlight.pwm_freq_hz; + DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz\n", freq); + if (!freq) { + DRM_DEBUG_KMS("Use panel default backlight frequency\n"); + return max_backlight; + } + + fxp = DIV_ROUND_CLOSEST(KHz(DP_EDP_BACKLIGHT_FREQ_BASE_KHZ), freq); + + /* Use highest possible value of Pn for more granularity of brightness + * adjustment while satifying the conditions below. + * - Pn is in the range of Pn_min and Pn_max + * - F is in the range of 1 and 255 + * - FxP is within 25% of desired value. + * Note: 25% is arbitrary value and may need some tweak. + */ + if (drm_dp_dpcd_readb(&intel_dp->aux, + DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min) != 1) { + DRM_DEBUG_KMS("Failed to read pwmgen bit count cap min\n"); + return max_backlight; + } + if (drm_dp_dpcd_readb(&intel_dp->aux, + DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max) != 1) { + DRM_DEBUG_KMS("Failed to read pwmgen bit count cap max\n"); + return max_backlight; + } + pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK; + pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK; + + fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4); + fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4); + if (fxp_min < (1 << pn_min) || (255 << pn_max) < fxp_max) { + DRM_DEBUG_KMS("VBT defined backlight frequency out of range\n"); + return max_backlight; + } + + for (pn = pn_max; pn >= pn_min; pn--) { + f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255); + fxp_actual = f << pn; + if (fxp_min <= fxp_actual && fxp_actual <= fxp_max) + break; + } + + DRM_DEBUG_KMS("Using eDP pwmgen bit count of %d\n", pn); + if (drm_dp_dpcd_writeb(&intel_dp->aux, + DP_EDP_PWMGEN_BIT_COUNT, pn) < 0) { + DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n"); + return max_backlight; + } + panel->backlight.pwmgen_bit_count = pn; + + max_backlight = (1 << pn) - 1; + + return max_backlight; +} + static int intel_dp_aux_setup_backlight(struct intel_connector *connector, enum pipe pipe) { - struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder); struct intel_panel *panel = &connector->panel; - if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT) - panel->backlight.max = 0xFFFF; - else - panel->backlight.max = 0xFF; + panel->backlight.max = intel_dp_aux_calc_max_backlight(connector); + if (!panel->backlight.max) + return -ENODEV; panel->backlight.min = 0; panel->backlight.level = intel_dp_aux_get_backlight(connector); - panel->backlight.enabled = panel->backlight.level != 0; return 0; -- 2.24.1

For eDP panels, it appears it's expected that so long as the panel is in DPCD control mode that the brightness value is never set to 0. Instead, if the desired effect is to set the panel's backlight to 0 we're expected to simply turn off the backlight through the DP_EDP_DISPLAY_CONTROL_REGISTER. We already do the latter correctly in intel_dp_aux_disable_backlight(). But, we make the mistake of writing the DPCD registers in the wrong order when enabling the backlight in intel_dp_aux_enable_backlight() since we currently enable the backlight through DP_EDP_DISPLAY_CONTROL_REGISTER before writing the brightness level. On the X1 Extreme 2nd Generation, this appears to have the potential of confusing the panel in such a way that further attempts to set the brightness don't actually change the backlight as expected and leave it off. Presumably, this happens because the incorrect register writing order briefly leaves the panel with DPCD mode enabled and a 0 brightness level set. So, reverse the order we write the DPCD registers when enabling the panel backlight so that we write the brightness value first, and enable the backlight second. This fix appears to be the final bit needed to get the backlight on the ThinkPad X1 Extreme 2nd Generation's AMOLED screen working. Tested-by: AceLan Kao <acelan.kao(a)canonical.com&gt; Tested-by: Perry Yuan <pyuan(a)redhat.com&gt; Signed-off-by: Lyude Paul <lyude(a)redhat.com&gt; Signed-off-by: Jani Nikula <jani.nikula(a)intel.com&gt; Link: https://patchwork.freedesktop.org/patch/msgid/20200116211623.53799-4-lyud... --- drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 5d4db5f8a165..77a759361c5c 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -207,8 +207,9 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st } } + intel_dp_aux_set_backlight(conn_state, + connector->panel.backlight.level); set_aux_backlight_enable(intel_dp, true); - intel_dp_aux_set_backlight(conn_state, connector->panel.backlight.level); } static void intel_dp_aux_disable_backlight(const struct drm_connector_state *old_conn_state) -- 2.24.1

The whole point of using OUIs is so that we can recognize certain devices and potentially apply quirks for them. Normally this should work quite well, but there appears to be quite a number of laptop panels out there that will fill the OUI but not the device ID. As such, for devices like this I can't imagine it's a very good idea to try relying on OUIs for applying quirks. As well, some laptop vendors have confirmed to us that their panels have this exact issue. So, let's introduce the ability to apply DP quirks based on EDID identification. We reuse the same quirk bits for OUI-based quirks, so that callers can simply check all possible quirks using drm_dp_has_quirk(). Signed-off-by: Lyude Paul <lyude(a)redhat.com&gt; Reviewed-by: Adam Jackson <ajax(a)redhat.com&gt; Cc: Jani Nikula <jani.nikula(a)intel.com&gt; --- drivers/gpu/drm/drm_dp_helper.c | 61 +++++++++++++++++++ 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 | 11 ++-- drivers/gpu/drm/i915/display/intel_dp_mst.c | 2 +- drivers/gpu/drm/i915/display/intel_psr.c | 2 +- include/drm/drm_dp_helper.h | 11 +++- 7 files changed, 81 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index a5364b5192b8..9b2ea2ae0204 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -1222,6 +1222,67 @@ 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[] = { +}; + +#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 cce0b1bba591..685c35e67144 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -5461,7 +5461,8 @@ 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, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) && + if (drm_dp_has_quirk(&desc, 0, + 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 778bd30743e5..8e3c5569603b 100644 --- a/drivers/gpu/drm/i915/display/intel_display_types.h +++ b/drivers/gpu/drm/i915/display/intel_display_types.h @@ -1253,6 +1253,7 @@ 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 c7424e2a04a3..e20b85ff937d 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -2373,7 +2373,7 @@ 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, + bool constant_n = drm_dp_has_quirk(&intel_dp->desc, 0, DP_DPCD_QUIRK_CONSTANT_N); int ret = 0, output_bpp; @@ -4466,7 +4466,8 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp) * it don't care about read it here and in intel_edp_init_dpcd(). */ if (!intel_dp_is_edp(intel_dp) && - !drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_NO_SINK_COUNT)) { + !drm_dp_has_quirk(&intel_dp->desc, 0, + DP_DPCD_QUIRK_NO_SINK_COUNT)) { u8 count; ssize_t r; @@ -5631,6 +5632,7 @@ intel_dp_set_edid(struct intel_dp *intel_dp) intel_dp->has_audio = drm_detect_monitor_audio(edid); drm_dp_cec_set_edid(&intel_dp->aux, edid); + intel_dp->edid_quirks = drm_dp_get_edid_quirks(edid); } static void @@ -5643,6 +5645,7 @@ intel_dp_unset_edid(struct intel_dp *intel_dp) intel_connector->detect_edid = NULL; intel_dp->has_audio = false; + intel_dp->edid_quirks = 0; } static int @@ -7356,8 +7359,8 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp, edid = drm_get_edid(connector, &intel_dp->aux.ddc); if (edid) { if (drm_add_edid_modes(connector, edid)) { - drm_connector_update_edid_property(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 cba68c5a80fa..4a1a2f868423 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c @@ -50,7 +50,7 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder, const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode; void *port = connector->port; - bool constant_n = drm_dp_has_quirk(&intel_dp->desc, + bool constant_n = drm_dp_has_quirk(&intel_dp->desc, 0, DP_DPCD_QUIRK_CONSTANT_N); int bpp, slots = -EINVAL; diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c index 83025052c965..82ba5624d14f 100644 --- a/drivers/gpu/drm/i915/display/intel_psr.c +++ b/drivers/gpu/drm/i915/display/intel_psr.c @@ -282,7 +282,7 @@ void intel_psr_init_dpcd(struct intel_dp *intel_dp) DRM_DEBUG_KMS("eDP panel supports PSR version %x\n", intel_dp->psr_dpcd[0]); - if (drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_NO_PSR)) { + if (drm_dp_has_quirk(&intel_dp->desc, 0, DP_DPCD_QUIRK_NO_PSR)) { DRM_DEBUG_KMS("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 bc04467f7c3a..1fe49e202dfb 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -1493,13 +1493,16 @@ 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. + * 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(). */ enum drm_dp_quirk { /** @@ -1535,14 +1538,16 @@ enum drm_dp_quirk { /** * drm_dp_has_quirk() - does the DP device have a specific quirk * @desc: Device decriptor 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, enum drm_dp_quirk quirk) +drm_dp_has_quirk(const struct drm_dp_desc *desc, u32 edid_quirks, + enum drm_dp_quirk quirk) { - return desc->quirks & BIT(quirk); + return (desc->quirks | edid_quirks) & BIT(quirk); } #ifdef CONFIG_DRM_DP_CEC -- 2.24.1

According to Dell, trying to match their panels via OUI is not reliable enough and we've been told that we should check against the EDID instead. As well, Dell seems to have some panels that are actually intended to switch between using PWM for backlight controls and DPCD for backlight controls depending on whether or not the panel is in HDR or SDR mode. Yikes. Regardless, we need to add quirks for these so that DPCD backlight controls get enabled by default, since without additional driver support that's the only form of brightness control that will work. Hopefully in the future we can remove these quirks once we have a better way of probing for this. Changes since v1: * Add one more EDID per Dell's request * Remove model number (which is possibly wrong) and replace with Dell CML 2020 systems Signed-off-by: Lyude Paul <lyude(a)redhat.com&gt; Reviewed-by: Adam Jackson <ajax(a)redhat.com&gt; Cc: Jani Nikula <jani.nikula(a)intel.com&gt; --- drivers/gpu/drm/drm_dp_helper.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 026f701eac69..d3a636a925d4 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -1241,6 +1241,20 @@ static const struct edid_quirk edid_quirk_list[] = { * 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) }, }; #undef MFG -- 2.24.1