[PATCH v2 0/2] GPD Win Max display fixes

[PATCH v2 0/2] GPD Win Max display fixes

[Anisse Astier]

This patch series is for making the GPD Win Max display usable with
Linux.

The GPD Win Max is a small laptop, and its eDP panel does not send an
EDID over DPCD; the EDID is instead available in the intel opregion, in
mailbox #5 [1]

The first patch is based on Jani's patch series [2] adding support for
the opregion, with changes. I've changed authorship, but I'd be glad to
revert it

The second patch is just to fix the orientation of the panel.

Changes since v1:
 - rebased on drm-tip
 - squashed patch 1 & 2
 - picked up Reviewed-by from Hans de Goede (thanks for the review)


[1]: https://gitlab.freedesktop.org/drm/intel/-/issues/3454
[2]: https://patchwork.kernel.org/project/intel-gfx/patch/20200828061941.17051-1-jani.nikula@intel.com/

Anisse Astier (2):
  drm/i915/opregion: add support for mailbox #5 EDID
  drm: Add orientation quirk for GPD Win Max

 .../gpu/drm/drm_panel_orientation_quirks.c    |  6 ++
 drivers/gpu/drm/i915/display/intel_dp.c       |  3 +
 drivers/gpu/drm/i915/display/intel_opregion.c | 69 ++++++++++++++++++-
 drivers/gpu/drm/i915/display/intel_opregion.h |  8 +++
 4 files changed, 85 insertions(+), 1 deletion(-)

-- 
2.31.1

[PATCH v2 1/2] drm/i915/opregion: add support for mailbox #5 EDID

[Anisse Astier]

The ACPI OpRegion Mailbox #5 ASLE extension may contain an EDID to be
used for the embedded display. Add support for using it via by adding
the EDID to the list of available modes on the connector, and use it for
eDP when available.

If a panel's EDID is broken, there may be an override EDID set in the
ACPI OpRegion mailbox #5. Use it if available.

Fixes the GPD Win Max display.

Based on original patch series by: Jani Nikula <jani.nikula@intel.com>
https://patchwork.kernel.org/project/intel-gfx/patch/20200828061941.17051-1-jani.nikula@intel.com/

Changes:
 - EDID is copied and validated with drm_edid_is_valid
 - Mode is now added via drm_add_edid_modes instead of using override
   mechanism
 - squashed the two patches

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anisse Astier <anisse@astier.eu>
---
 drivers/gpu/drm/i915/display/intel_dp.c       |  3 +
 drivers/gpu/drm/i915/display/intel_opregion.c | 69 ++++++++++++++++++-
 drivers/gpu/drm/i915/display/intel_opregion.h |  8 +++
 3 files changed, 79 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 5c9222283044..43fb485c0e02 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -5191,6 +5191,9 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 		goto out_vdd_off;
 	}
 
+	/* Set up override EDID, if any, from ACPI OpRegion */
+	intel_opregion_edid_probe(intel_connector);
+
 	mutex_lock(&dev->mode_config.mutex);
 	edid = drm_get_edid(connector, &intel_dp->aux.ddc);
 	if (edid) {
diff --git a/drivers/gpu/drm/i915/display/intel_opregion.c b/drivers/gpu/drm/i915/display/intel_opregion.c
index dfd724e506b5..ef8d38f041eb 100644
--- a/drivers/gpu/drm/i915/display/intel_opregion.c
+++ b/drivers/gpu/drm/i915/display/intel_opregion.c
@@ -196,6 +196,8 @@ struct opregion_asle_ext {
 #define ASLE_IUER_WINDOWS_BTN		(1 << 1)
 #define ASLE_IUER_POWER_BTN		(1 << 0)
 
+#define ASLE_PHED_EDID_VALID_MASK	0x3
+
 /* Software System Control Interrupt (SWSCI) */
 #define SWSCI_SCIC_INDICATOR		(1 << 0)
 #define SWSCI_SCIC_MAIN_FUNCTION_SHIFT	1
@@ -909,8 +911,10 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
 		opregion->asle->ardy = ASLE_ARDY_NOT_READY;
 	}
 
-	if (mboxes & MBOX_ASLE_EXT)
+	if (mboxes & MBOX_ASLE_EXT) {
 		drm_dbg(&dev_priv->drm, "ASLE extension supported\n");
+		opregion->asle_ext = base + OPREGION_ASLE_EXT_OFFSET;
+	}
 
 	if (intel_load_vbt_firmware(dev_priv) == 0)
 		goto out;
@@ -1037,6 +1041,68 @@ intel_opregion_get_panel_type(struct drm_i915_private *dev_priv)
 	return ret - 1;
 }
 
+/**
+ * intel_opregion_edid_probe - Add EDID from ACPI OpRegion mailbox #5
+ * @intel_connector: eDP connector
+ *
+ * This reads the ACPI Opregion mailbox #5 to extract the EDID that is passed
+ * to it.
+ *
+ * Will take a lock on the DRM mode_config to add the EDID; make sure it isn't
+ * called with lock taken.
+ *
+ */
+void intel_opregion_edid_probe(struct intel_connector *intel_connector)
+{
+	struct drm_connector *connector = &intel_connector->base;
+	struct drm_i915_private *i915 = to_i915(connector->dev);
+	struct intel_opregion *opregion = &i915->opregion;
+	const void *in_edid;
+	const struct edid *edid;
+	struct edid *new_edid;
+	int len, ret, num;
+
+	if (!opregion->asle_ext || connector->override_edid)
+		return;
+
+	in_edid = opregion->asle_ext->bddc;
+
+	/* Validity corresponds to number of 128-byte blocks */
+	len = (opregion->asle_ext->phed & ASLE_PHED_EDID_VALID_MASK) * 128;
+	if (!len || !memchr_inv(in_edid, 0, len))
+		return;
+
+	edid = in_edid;
+
+	if (len < EDID_LENGTH * (1 + edid->extensions)) {
+		drm_dbg_kms(&i915->drm, "Invalid EDID in ACPI OpRegion (Mailbox #5)\n");
+		return;
+	}
+	new_edid = drm_edid_duplicate(edid);
+	if (!new_edid) {
+		drm_err(&i915->drm, "Cannot duplicate EDID\n");
+		return;
+	}
+	if (!drm_edid_is_valid(new_edid)) {
+		kfree(new_edid);
+		drm_dbg_kms(&i915->drm, "Cannot validate EDID in ACPI OpRegion (Mailbox #5)\n");
+		return;
+	}
+
+	ret = drm_connector_update_edid_property(connector, new_edid);
+	if (ret) {
+		kfree(new_edid);
+		return;
+	}
+
+	mutex_lock(&connector->dev->mode_config.mutex);
+	num = drm_add_edid_modes(connector, new_edid);
+	mutex_unlock(&connector->dev->mode_config.mutex);
+
+	drm_dbg_kms(&i915->drm, "Using OpRegion EDID for [CONNECTOR:%d:%s], added %d mode(s)\n",
+		    connector->base.id, connector->name, num);
+}
+
 void intel_opregion_register(struct drm_i915_private *i915)
 {
 	struct intel_opregion *opregion = &i915->opregion;
@@ -1127,6 +1193,7 @@ void intel_opregion_unregister(struct drm_i915_private *i915)
 	opregion->acpi = NULL;
 	opregion->swsci = NULL;
 	opregion->asle = NULL;
+	opregion->asle_ext = NULL;
 	opregion->vbt = NULL;
 	opregion->lid_state = NULL;
 }
diff --git a/drivers/gpu/drm/i915/display/intel_opregion.h b/drivers/gpu/drm/i915/display/intel_opregion.h
index 4aa68ffbd30e..c1ecfcbb6f55 100644
--- a/drivers/gpu/drm/i915/display/intel_opregion.h
+++ b/drivers/gpu/drm/i915/display/intel_opregion.h
@@ -29,12 +29,14 @@
 #include <linux/pci.h>
 
 struct drm_i915_private;
+struct intel_connector;
 struct intel_encoder;
 
 struct opregion_header;
 struct opregion_acpi;
 struct opregion_swsci;
 struct opregion_asle;
+struct opregion_asle_ext;
 
 struct intel_opregion {
 	struct opregion_header *header;
@@ -43,6 +45,7 @@ struct intel_opregion {
 	u32 swsci_gbda_sub_functions;
 	u32 swsci_sbcb_sub_functions;
 	struct opregion_asle *asle;
+	struct opregion_asle_ext *asle_ext;
 	void *rvda;
 	void *vbt_firmware;
 	const void *vbt;
@@ -71,6 +74,7 @@ int intel_opregion_notify_encoder(struct intel_encoder *intel_encoder,
 int intel_opregion_notify_adapter(struct drm_i915_private *dev_priv,
 				  pci_power_t state);
 int intel_opregion_get_panel_type(struct drm_i915_private *dev_priv);
+void intel_opregion_edid_probe(struct intel_connector *connector);
 
 #else /* CONFIG_ACPI*/
 
@@ -117,6 +121,10 @@ static inline int intel_opregion_get_panel_type(struct drm_i915_private *dev)
 	return -ENODEV;
 }
 
+void intel_opregion_edid_probe(struct intel_connector *connector)
+{
+}
+
 #endif /* CONFIG_ACPI */
 
 #endif
-- 
2.31.1

[PATCH v2 2/2] drm: Add orientation quirk for GPD Win Max

[Anisse Astier]

Panel is 800x1280, but mounted on a laptop form factor, sideways.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Anisse Astier <anisse@astier.eu>
---
 drivers/gpu/drm/drm_panel_orientation_quirks.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/drm_panel_orientation_quirks.c b/drivers/gpu/drm/drm_panel_orientation_quirks.c
index f6bdec7fa925..3c3f4ed89173 100644
--- a/drivers/gpu/drm/drm_panel_orientation_quirks.c
+++ b/drivers/gpu/drm/drm_panel_orientation_quirks.c
@@ -148,6 +148,12 @@ static const struct dmi_system_id orientation_data[] = {
 		  DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "MicroPC"),
 		},
 		.driver_data = (void *)&lcd720x1280_rightside_up,
+	}, {	/* GPD Win Max */
+		.matches = {
+		  DMI_EXACT_MATCH(DMI_SYS_VENDOR, "GPD"),
+		  DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "G1619-01"),
+		},
+		.driver_data = (void *)&lcd800x1280_rightside_up,
 	}, {	/*
 		 * GPD Pocket, note that the the DMI data is less generic then
 		 * it seems, devices with a board-vendor of "AMI Corporation"
-- 
2.31.1

Re: [PATCH v2 1/2] drm/i915/opregion: add support for mailbox #5 EDID

[Ville Syrjälä]

On Mon, May 31, 2021 at 10:46:41PM +0200, Anisse Astier wrote:
> The ACPI OpRegion Mailbox #5 ASLE extension may contain an EDID to be
> used for the embedded display. Add support for using it via by adding
> the EDID to the list of available modes on the connector, and use it for
> eDP when available.
> 
> If a panel's EDID is broken, there may be an override EDID set in the
> ACPI OpRegion mailbox #5. Use it if available.

Looks like Windows uses the ACPI _DDC method instead. We should probably
do the same, just in case some crazy machine stores the EDID somewhere
else.

> 
> Fixes the GPD Win Max display.
> 
> Based on original patch series by: Jani Nikula <jani.nikula@intel.com>
> https://patchwork.kernel.org/project/intel-gfx/patch/20200828061941.17051-1-jani.nikula@intel.com/
> 
> Changes:
>  - EDID is copied and validated with drm_edid_is_valid
>  - Mode is now added via drm_add_edid_modes instead of using override
>    mechanism
>  - squashed the two patches
> 
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Uma Shankar <uma.shankar@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Anisse Astier <anisse@astier.eu>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c       |  3 +
>  drivers/gpu/drm/i915/display/intel_opregion.c | 69 ++++++++++++++++++-
>  drivers/gpu/drm/i915/display/intel_opregion.h |  8 +++
>  3 files changed, 79 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 5c9222283044..43fb485c0e02 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -5191,6 +5191,9 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  		goto out_vdd_off;
>  	}
>  
> +	/* Set up override EDID, if any, from ACPI OpRegion */
> +	intel_opregion_edid_probe(intel_connector);
> +
>  	mutex_lock(&dev->mode_config.mutex);
>  	edid = drm_get_edid(connector, &intel_dp->aux.ddc);
>  	if (edid) {
> diff --git a/drivers/gpu/drm/i915/display/intel_opregion.c b/drivers/gpu/drm/i915/display/intel_opregion.c
> index dfd724e506b5..ef8d38f041eb 100644
> --- a/drivers/gpu/drm/i915/display/intel_opregion.c
> +++ b/drivers/gpu/drm/i915/display/intel_opregion.c
> @@ -196,6 +196,8 @@ struct opregion_asle_ext {
>  #define ASLE_IUER_WINDOWS_BTN		(1 << 1)
>  #define ASLE_IUER_POWER_BTN		(1 << 0)
>  
> +#define ASLE_PHED_EDID_VALID_MASK	0x3
> +
>  /* Software System Control Interrupt (SWSCI) */
>  #define SWSCI_SCIC_INDICATOR		(1 << 0)
>  #define SWSCI_SCIC_MAIN_FUNCTION_SHIFT	1
> @@ -909,8 +911,10 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
>  		opregion->asle->ardy = ASLE_ARDY_NOT_READY;
>  	}
>  
> -	if (mboxes & MBOX_ASLE_EXT)
> +	if (mboxes & MBOX_ASLE_EXT) {
>  		drm_dbg(&dev_priv->drm, "ASLE extension supported\n");
> +		opregion->asle_ext = base + OPREGION_ASLE_EXT_OFFSET;
> +	}
>  
>  	if (intel_load_vbt_firmware(dev_priv) == 0)
>  		goto out;
> @@ -1037,6 +1041,68 @@ intel_opregion_get_panel_type(struct drm_i915_private *dev_priv)
>  	return ret - 1;
>  }
>  
> +/**
> + * intel_opregion_edid_probe - Add EDID from ACPI OpRegion mailbox #5
> + * @intel_connector: eDP connector
> + *
> + * This reads the ACPI Opregion mailbox #5 to extract the EDID that is passed
> + * to it.
> + *
> + * Will take a lock on the DRM mode_config to add the EDID; make sure it isn't
> + * called with lock taken.
> + *
> + */
> +void intel_opregion_edid_probe(struct intel_connector *intel_connector)
> +{
> +	struct drm_connector *connector = &intel_connector->base;
> +	struct drm_i915_private *i915 = to_i915(connector->dev);
> +	struct intel_opregion *opregion = &i915->opregion;
> +	const void *in_edid;
> +	const struct edid *edid;
> +	struct edid *new_edid;
> +	int len, ret, num;
> +
> +	if (!opregion->asle_ext || connector->override_edid)
> +		return;
> +
> +	in_edid = opregion->asle_ext->bddc;
> +
> +	/* Validity corresponds to number of 128-byte blocks */
> +	len = (opregion->asle_ext->phed & ASLE_PHED_EDID_VALID_MASK) * 128;
> +	if (!len || !memchr_inv(in_edid, 0, len))
> +		return;
> +
> +	edid = in_edid;
> +
> +	if (len < EDID_LENGTH * (1 + edid->extensions)) {
> +		drm_dbg_kms(&i915->drm, "Invalid EDID in ACPI OpRegion (Mailbox #5)\n");
> +		return;
> +	}
> +	new_edid = drm_edid_duplicate(edid);
> +	if (!new_edid) {
> +		drm_err(&i915->drm, "Cannot duplicate EDID\n");
> +		return;
> +	}
> +	if (!drm_edid_is_valid(new_edid)) {
> +		kfree(new_edid);
> +		drm_dbg_kms(&i915->drm, "Cannot validate EDID in ACPI OpRegion (Mailbox #5)\n");
> +		return;
> +	}
> +
> +	ret = drm_connector_update_edid_property(connector, new_edid);
> +	if (ret) {
> +		kfree(new_edid);
> +		return;
> +	}
> +
> +	mutex_lock(&connector->dev->mode_config.mutex);
> +	num = drm_add_edid_modes(connector, new_edid);
> +	mutex_unlock(&connector->dev->mode_config.mutex);
> +
> +	drm_dbg_kms(&i915->drm, "Using OpRegion EDID for [CONNECTOR:%d:%s], added %d mode(s)\n",
> +		    connector->base.id, connector->name, num);
> +}
> +
>  void intel_opregion_register(struct drm_i915_private *i915)
>  {
>  	struct intel_opregion *opregion = &i915->opregion;
> @@ -1127,6 +1193,7 @@ void intel_opregion_unregister(struct drm_i915_private *i915)
>  	opregion->acpi = NULL;
>  	opregion->swsci = NULL;
>  	opregion->asle = NULL;
> +	opregion->asle_ext = NULL;
>  	opregion->vbt = NULL;
>  	opregion->lid_state = NULL;
>  }
> diff --git a/drivers/gpu/drm/i915/display/intel_opregion.h b/drivers/gpu/drm/i915/display/intel_opregion.h
> index 4aa68ffbd30e..c1ecfcbb6f55 100644
> --- a/drivers/gpu/drm/i915/display/intel_opregion.h
> +++ b/drivers/gpu/drm/i915/display/intel_opregion.h
> @@ -29,12 +29,14 @@
>  #include <linux/pci.h>
>  
>  struct drm_i915_private;
> +struct intel_connector;
>  struct intel_encoder;
>  
>  struct opregion_header;
>  struct opregion_acpi;
>  struct opregion_swsci;
>  struct opregion_asle;
> +struct opregion_asle_ext;
>  
>  struct intel_opregion {
>  	struct opregion_header *header;
> @@ -43,6 +45,7 @@ struct intel_opregion {
>  	u32 swsci_gbda_sub_functions;
>  	u32 swsci_sbcb_sub_functions;
>  	struct opregion_asle *asle;
> +	struct opregion_asle_ext *asle_ext;
>  	void *rvda;
>  	void *vbt_firmware;
>  	const void *vbt;
> @@ -71,6 +74,7 @@ int intel_opregion_notify_encoder(struct intel_encoder *intel_encoder,
>  int intel_opregion_notify_adapter(struct drm_i915_private *dev_priv,
>  				  pci_power_t state);
>  int intel_opregion_get_panel_type(struct drm_i915_private *dev_priv);
> +void intel_opregion_edid_probe(struct intel_connector *connector);
>  
>  #else /* CONFIG_ACPI*/
>  
> @@ -117,6 +121,10 @@ static inline int intel_opregion_get_panel_type(struct drm_i915_private *dev)
>  	return -ENODEV;
>  }
>  
> +void intel_opregion_edid_probe(struct intel_connector *connector)
> +{
> +}
> +
>  #endif /* CONFIG_ACPI */
>  
>  #endif
> -- 
> 2.31.1

-- 
Ville Syrjälä
Intel

Re: [PATCH v2 1/2] drm/i915/opregion: add support for mailbox #5 EDID

[Anisse Astier]

Le Tue, Jun 01, 2021 at 06:50:24PM +0300, Ville Syrj?l? a ?crit :
> On Mon, May 31, 2021 at 10:46:41PM +0200, Anisse Astier wrote:
> > The ACPI OpRegion Mailbox #5 ASLE extension may contain an EDID to be
> > used for the embedded display. Add support for using it via by adding
> > the EDID to the list of available modes on the connector, and use it for
> > eDP when available.
> > 
> > If a panel's EDID is broken, there may be an override EDID set in the
> > ACPI OpRegion mailbox #5. Use it if available.
> 
> Looks like Windows uses the ACPI _DDC method instead. We should probably
> do the same, just in case some crazy machine stores the EDID somewhere
> else.

Thanks, I wouldn't have thought of this. It seems Daniel Dadap did a
patch series to do just that, in a generic way:
https://lore.kernel.org/amd-gfx/20200727205357.27839-1-ddadap@nvidia.com/

I've tried patch 1 & 2, and after a fix[1] was able to call the _DDC method
on most devices, but without any EDID being returned.

I looked at the disassembled ACPI tables[2], and could not find any
device with the _DDC method. Are you sure it's the only method the
Windows driver uses to get the EDID ?

Regards,

Anisse

[1] _DOD ids should only use 16 lower bits, see table here:
https://uefi.org/specs/ACPI/6.4/Apx_B_Video_Extensions/display-specific-methods.html#dod-enumerate-all-devices-attached-to-the-display-adapter
[2] acpidump: https://gitlab.freedesktop.org/drm/intel/-/issues/3454#note_913970

Re: [PATCH v2 1/2] drm/i915/opregion: add support for mailbox #5 EDID

[Daniel Dadap]

On 6/1/21 5:43 PM, Anisse Astier wrote:
>
> Le Tue, Jun 01, 2021 at 06:50:24PM +0300, Ville Syrj?l? a ?crit :
>> On Mon, May 31, 2021 at 10:46:41PM +0200, Anisse Astier wrote:
>>> The ACPI OpRegion Mailbox #5 ASLE extension may contain an EDID to be
>>> used for the embedded display. Add support for using it via by adding
>>> the EDID to the list of available modes on the connector, and use it for
>>> eDP when available.
>>>
>>> If a panel's EDID is broken, there may be an override EDID set in the
>>> ACPI OpRegion mailbox #5. Use it if available.
>> Looks like Windows uses the ACPI _DDC method instead. We should probably
>> do the same, just in case some crazy machine stores the EDID somewhere
>> else.
> Thanks, I wouldn't have thought of this. It seems Daniel Dadap did a
> patch series to do just that, in a generic way:
> https://lore.kernel.org/amd-gfx/20200727205357.27839-1-ddadap@nvidia.com/
>
> I've tried patch 1 & 2, and after a fix[1] was able to call the _DDC method
> on most devices, but without any EDID being returned.
>
> I looked at the disassembled ACPI tables[2], and could not find any
> device with the _DDC method. Are you sure it's the only method the
> Windows driver uses to get the EDID ?


_DDC only works on devices that actually implement it, and the vast 
majority of devices don't, because the display just provides an EDID 
normally. AIUI, usually a device will implement _DDC either because an 
embedded panel has no ROM of its own to deliver an EDID, or to allow the 
EDID to be read by either GPU on a system with a muxed display, 
regardless of which GPU happens to have the DDC lines (in TMDS) or DP 
AUX routed to it at the moment. (To my knowledge, nobody actually muxes 
DP AUX independently from the main link, but there were some older 
pre-DP designs where DDC could be muxed independently.)

I'm not sure whether the comment about Windows using _DDC was meant for 
this device in particular, or just more generally, since DDC is part of 
the ACPI spec and some Windows GPU drivers *do* use it, where available. 
If it was meant for a particular device, then it's possible that the 
ACPI tables advertise different methods depending on e.g. _OSI. If you 
haven't already tried doing so, it might be worth overriding _OSI to 
spoof Windows, to see if _DDC gets advertised.

I'm not sure how you were able to call _DDC without an EDID being 
returned as described above, if there was no _DDC method in the ACPI 
tables; I would expect that attempting to call _DDC would fail to locate 
a suitable method and do_acpi_ddc would return NULL.


> Regards,
>
> Anisse
>
> [1] _DOD ids should only use 16 lower bits, see table here:
> https://uefi.org/specs/ACPI/6.4/Apx_B_Video_Extensions/display-specific-methods.html#dod-enumerate-all-devices-attached-to-the-display-adapter


Thanks; I don't see a version of your modified patch here, was the fix 
just to mask the _DOD IDs against 0xffff?


> [2] acpidump: https://gitlab.freedesktop.org/drm/intel/-/issues/3454#note_913970
>

Re: [PATCH v2 1/2] drm/i915/opregion: add support for mailbox #5 EDID

[Anisse Astier]

Le Wed, Jul 07, 2021 at 02:57:47PM -0500, Daniel Dadap a écrit :
> On 6/1/21 5:43 PM, Anisse Astier wrote:
> > 
> > Le Tue, Jun 01, 2021 at 06:50:24PM +0300, Ville Syrj?l? a ?crit :
> > > On Mon, May 31, 2021 at 10:46:41PM +0200, Anisse Astier wrote:
> > > > The ACPI OpRegion Mailbox #5 ASLE extension may contain an EDID to be
> > > > used for the embedded display. Add support for using it via by adding
> > > > the EDID to the list of available modes on the connector, and use it for
> > > > eDP when available.
> > > > 
> > > > If a panel's EDID is broken, there may be an override EDID set in the
> > > > ACPI OpRegion mailbox #5. Use it if available.
> > > Looks like Windows uses the ACPI _DDC method instead. We should probably
> > > do the same, just in case some crazy machine stores the EDID somewhere
> > > else.
> > Thanks, I wouldn't have thought of this. It seems Daniel Dadap did a
> > patch series to do just that, in a generic way:
> > https://lore.kernel.org/amd-gfx/20200727205357.27839-1-ddadap@nvidia.com/
> > 
> > I've tried patch 1 & 2, and after a fix[1] was able to call the _DDC method
> > on most devices, but without any EDID being returned.
> > 
> > I looked at the disassembled ACPI tables[2], and could not find any
> > device with the _DDC method. Are you sure it's the only method the
> > Windows driver uses to get the EDID ?
> 
> 
> _DDC only works on devices that actually implement it, and the vast majority
> of devices don't, because the display just provides an EDID normally. AIUI,
> usually a device will implement _DDC either because an embedded panel has no
> ROM of its own to deliver an EDID, or to allow the EDID to be read by either
> GPU on a system with a muxed display, regardless of which GPU happens to
> have the DDC lines (in TMDS) or DP AUX routed to it at the moment. (To my
> knowledge, nobody actually muxes DP AUX independently from the main link,
> but there were some older pre-DP designs where DDC could be muxed
> independently.)
> 
> I'm not sure whether the comment about Windows using _DDC was meant for this
> device in particular, or just more generally, since DDC is part of the ACPI
> spec and some Windows GPU drivers *do* use it, where available. If it was
> meant for a particular device, then it's possible that the ACPI tables
> advertise different methods depending on e.g. _OSI. If you haven't already
> tried doing so, it might be worth overriding _OSI to spoof Windows, to see
> if _DDC gets advertised.

I think it's already the default Linux behaviour according to
https://www.kernel.org/doc/html/latest/firmware-guide/acpi/osi.html

I added a few specific Windows versions (2007 - 2020), but did not see
any difference.


> 
> I'm not sure how you were able to call _DDC without an EDID being returned
> as described above, if there was no _DDC method in the ACPI tables; I would
> expect that attempting to call _DDC would fail to locate a suitable method
> and do_acpi_ddc would return NULL.

I wasn't, I just tried calling the method on all devices (removing the
_DOD id check), but obviously it failed because it did not exist.

> 
> 
> > Regards,
> > 
> > Anisse
> > 
> > [1] _DOD ids should only use 16 lower bits, see table here:
> > https://uefi.org/specs/ACPI/6.4/Apx_B_Video_Extensions/display-specific-methods.html#dod-enumerate-all-devices-attached-to-the-display-adapter
> 
> 
> Thanks; I don't see a version of your modified patch here, was the fix just
> to mask the _DOD IDs against 0xffff?

Yes, nothing fancy:

-                       if (adr == dod_entries[i]) {
+                       if (adr == (dod_entries[i] & 0xFFFF) ) {


Regards,

Anisse