Re: [PATCH v6 3/5] drm: Add support to get EDID from ACPI

Jani Nikula
2024-02-15T14:09:41Z

On Wed, 14 Feb 2024, Mario Limonciello <mario.limonciello@amd.com> wrote:
> Some manufacturers have intentionally put an EDID that differs from
> the EDID on the internal panel on laptops. Drivers that prefer to
> fetch this EDID can set a bit on the drm_connector to indicate that
> the DRM EDID helpers should try to fetch it and it is preferred if
> it's present.

I just replied to a previous version of the patch [1]. Looks like all
the comments there still hold.

BR,
Jani.

[1] https://lore.kernel.org/r/87eddd6d41.fsf@intel.com

>
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> drivers/gpu/drm/Kconfig | 1 +
> drivers/gpu/drm/drm_edid.c | 109 +++++++++++++++++++++++++++++++++---
> include/drm/drm_connector.h | 6 ++
> include/drm/drm_edid.h | 1 +
> 4 files changed, 109 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 872edb47bb53..3db89e6af01d 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -8,6 +8,7 @@
> menuconfig DRM
> tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
> depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> + depends on (ACPI_VIDEO || ACPI_VIDEO=n)
> select DRM_PANEL_ORIENTATION_QUIRKS
> select DRM_KMS_HELPER if DRM_FBDEV_EMULATION
> select FB_CORE if DRM_FBDEV_EMULATION
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 923c4423151c..cdc30c6d05d5 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -28,6 +28,7 @@
> * DEALINGS IN THE SOFTWARE.
> */
>
> +#include <acpi/video.h>
> #include <linux/bitfield.h>
> #include <linux/cec.h>
> #include <linux/hdmi.h>
> @@ -2188,6 +2189,58 @@ drm_do_probe_ddc_edid(void *data, u8 *buf, unsigned int block, size_t len)
> return ret == xfers ? 0 : -1;
> }
>
> +/**
> + * drm_do_probe_acpi_edid() - get EDID information via ACPI _DDC
> + * @data: struct drm_connector
> + * @buf: EDID data buffer to be filled
> + * @block: 128 byte EDID block to start fetching from
> + * @len: EDID data buffer length to fetch
> + *
> + * Try to fetch EDID information by calling acpi_video_get_edid() function.
> + *
> + * Return: 0 on success or error code on failure.
> + */
> +static int
> +drm_do_probe_acpi_edid(void *data, u8 *buf, unsigned int block, size_t len)
> +{
> + struct drm_connector *connector = data;
> + struct drm_device *ddev = connector->dev;
> + struct acpi_device *acpidev = ACPI_COMPANION(ddev->dev);
> + unsigned char start = block * EDID_LENGTH;
> + void *edid;
> + int r;
> +
> + if (!acpidev)
> + return -ENODEV;
> +
> + switch (connector->connector_type) {
> + case DRM_MODE_CONNECTOR_LVDS:
> + case DRM_MODE_CONNECTOR_eDP:
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + /* fetch the entire edid from BIOS */
> + r = acpi_video_get_edid(acpidev, ACPI_VIDEO_DISPLAY_LCD, -1, &edid);
> + if (r < 0) {
> + DRM_DEBUG_KMS("Failed to get EDID from ACPI: %d\n", r);
> + return r;
> + }
> + if (len > r || start > r || start + len > r) {
> + r = -EINVAL;
> + goto cleanup;
> + }
> +
> + memcpy(buf, edid + start, len);
> + r = 0;
> +
> +cleanup:
> + kfree(edid);
> +
> + return r;
> +}
> +
> static void connector_bad_edid(struct drm_connector *connector,
> const struct edid *edid, int num_blocks)
> {
> @@ -2621,7 +2674,8 @@ EXPORT_SYMBOL(drm_probe_ddc);
> * @connector: connector we're probing
> * @adapter: I2C adapter to use for DDC
> *
> - * Poke the given I2C channel to grab EDID data if possible. If found,
> + * If the connector allows it, try to fetch EDID data using ACPI. If not found
> + * poke the given I2C channel to grab EDID data if possible. If found,
> * attach it to the connector.
> *
> * Return: Pointer to valid EDID or NULL if we couldn't find any.
> @@ -2629,20 +2683,50 @@ EXPORT_SYMBOL(drm_probe_ddc);
> struct edid *drm_get_edid(struct drm_connector *connector,
> struct i2c_adapter *adapter)
> {
> - struct edid *edid;
> + struct edid *edid = NULL;
>
> if (connector->force == DRM_FORCE_OFF)
> return NULL;
>
> - if (connector->force == DRM_FORCE_UNSPECIFIED && !drm_probe_ddc(adapter))
> - return NULL;
> + if (connector->acpi_edid_allowed)
> + edid = _drm_do_get_edid(connector, drm_do_probe_acpi_edid, connector, NULL);
> +
> + if (!edid) {
> + if (connector->force == DRM_FORCE_UNSPECIFIED && !drm_probe_ddc(adapter))
> + return NULL;
> + edid = _drm_do_get_edid(connector, drm_do_probe_ddc_edid, adapter, NULL);
> + }
>
> - edid = _drm_do_get_edid(connector, drm_do_probe_ddc_edid, adapter, NULL);
> drm_connector_update_edid_property(connector, edid);
> return edid;
> }
> EXPORT_SYMBOL(drm_get_edid);
>
> +/**
> + * drm_edid_read_acpi - get EDID data, if available
> + * @connector: connector we're probing
> + *
> + * Use the BIOS to attempt to grab EDID data if possible.
> + *
> + * The returned pointer must be freed using drm_edid_free().
> + *
> + * Return: Pointer to valid EDID or NULL if we couldn't find any.
> + */
> +const struct drm_edid *drm_edid_read_acpi(struct drm_connector *connector)
> +{
> + const struct drm_edid *drm_edid;
> +
> + if (connector->force == DRM_FORCE_OFF)
> + return NULL;
> +
> + drm_edid = drm_edid_read_custom(connector, drm_do_probe_acpi_edid, connector);
> +
> + /* Note: Do *not* call connector updates here. */
> +
> + return drm_edid;
> +}
> +EXPORT_SYMBOL(drm_edid_read_acpi);
> +
> /**
> * drm_edid_read_custom - Read EDID data using given EDID block read function
> * @connector: Connector to use
> @@ -2727,10 +2811,11 @@ const struct drm_edid *drm_edid_read_ddc(struct drm_connector *connector,
> EXPORT_SYMBOL(drm_edid_read_ddc);
>
> /**
> - * drm_edid_read - Read EDID data using connector's I2C adapter
> + * drm_edid_read - Read EDID data using BIOS or connector's I2C adapter
> * @connector: Connector to use
> *
> - * Read EDID using the connector's I2C adapter.
> + * Read EDID from BIOS if allowed by connector or by using the connector's
> + * I2C adapter.
> *
> * The EDID may be overridden using debugfs override_edid or firmware EDID
> * (drm_edid_load_firmware() and drm.edid_firmware parameter), in this priority
> @@ -2742,10 +2827,18 @@ EXPORT_SYMBOL(drm_edid_read_ddc);
> */
> const struct drm_edid *drm_edid_read(struct drm_connector *connector)
> {
> + const struct drm_edid *drm_edid = NULL;
> +
> if (drm_WARN_ON(connector->dev, !connector->ddc))
> return NULL;
>
> - return drm_edid_read_ddc(connector, connector->ddc);
> + if (connector->acpi_edid_allowed)
> + drm_edid = drm_edid_read_acpi(connector);
> +
> + if (!drm_edid)
> + drm_edid = drm_edid_read_ddc(connector, connector->ddc);
> +
> + return drm_edid;
> }
> EXPORT_SYMBOL(drm_edid_read);
>
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index fe88d7fc6b8f..74ed47f37a69 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -1886,6 +1886,12 @@ struct drm_connector {
>
> /** @hdr_sink_metadata: HDR Metadata Information read from sink */
> struct hdr_sink_metadata hdr_sink_metadata;
> +
> + /**
> + * @acpi_edid_allowed: Get the EDID from the BIOS, if available.
> + * This is only applicable to eDP and LVDS displays.
> + */
> + bool acpi_edid_allowed;
> };
>
> #define obj_to_connector(x) container_of(x, struct drm_connector, base)
> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> index 7923bc00dc7a..1c1ee927de9c 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -459,5 +459,6 @@ bool drm_edid_is_digital(const struct drm_edid *drm_edid);
>
> const u8 *drm_find_edid_extension(const struct drm_edid *drm_edid,
> int ext_id, int *ext_index);
> +const struct drm_edid *drm_edid_read_acpi(struct drm_connector *connector);
>
> #endif /* __DRM_EDID_H__ */

--
Jani Nikula, Intel