[PATCH v7 10/10] drm/amd/display: Fetch the EDID from _DDC if available for eDP

[Hamza Mahfooz]

On 9/19/24 13:29, Alex Deucher wrote:
> On Thu, Sep 19, 2024 at 12:06 PM Mario Limonciello
> <mario.limonciello at amd.com> wrote:
>>
>> On 9/19/2024 11:03, Alex Hung wrote:
>>> A minor comment (see inline below).
>>>
>>> Otherwise
>>>
>>> Reviewed-by: Alex Hung <alex.hung at amd.com>
>>>
>>> On 2024-09-18 15:38, Mario Limonciello wrote:
>>>> Some manufacturers have intentionally put an EDID that differs from
>>>> the EDID on the internal panel on laptops.
>>>>
>>>> Attempt to fetch this EDID if it exists and prefer it over the EDID
>>>> that is provided by the panel. If a user prefers to use the EDID from
>>>> the panel, offer a DC debugging parameter that would disable this.
>>>>
>>>> Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
>>>> ---
>>>>    .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 62 ++++++++++++++++++-
>>>>    drivers/gpu/drm/amd/include/amd_shared.h      |  5 ++
>>>>    2 files changed, 66 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
>>>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
>>>> index 8f4be7a1ec45..05d3e00ecce0 100644
>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
>>>> @@ -23,6 +23,8 @@
>>>>     *
>>>>     */
>>>> +#include <acpi/video.h>
>>>> +
>>>>    #include <linux/string.h>
>>>>    #include <linux/acpi.h>
>>>>    #include <linux/i2c.h>
>>>> @@ -874,6 +876,60 @@ bool dm_helpers_is_dp_sink_present(struct dc_link
>>>> *link)
>>>>        return dp_sink_present;
>>>>    }
>>>> +static int
>>>> +dm_helpers_probe_acpi_edid(void *data, u8 *buf, unsigned int block,
>>>> size_t len)
>>>> +{
>>>> +    struct drm_connector *connector = data;
>>>> +    struct acpi_device *acpidev = ACPI_COMPANION(connector->dev->dev);
>>>> +    unsigned char start = block * EDID_LENGTH;
>>>> +    void *edid;
>>>> +    int r;
>>>> +
>>>> +    if (!acpidev)
>>>> +        return -ENODEV;
>>>> +
>>>> +    /* 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 const struct drm_edid *
>>>> +dm_helpers_read_acpi_edid(struct amdgpu_dm_connector *aconnector)
>>>> +{
>>>> +    struct drm_connector *connector = &aconnector->base;
>>>> +
>>>> +    if (amdgpu_dc_debug_mask & DC_DISABLE_ACPI_EDID)
>>>> +        return NULL;
>>>> +
>>>> +    switch (connector->connector_type) {
>>>> +    case DRM_MODE_CONNECTOR_LVDS:
>>>> +    case DRM_MODE_CONNECTOR_eDP:
>>>> +        break;
>>>> +    default:
>>>> +        return NULL;
>>>> +    }
>>>> +
>>>> +    if (connector->force == DRM_FORCE_OFF)
>>>> +        return NULL;
>>>> +
>>>> +    return drm_edid_read_custom(connector,
>>>> dm_helpers_probe_acpi_edid, connector);
>>>> +}
>>>> +
>>>>    enum dc_edid_status dm_helpers_read_local_edid(
>>>>            struct dc_context *ctx,
>>>>            struct dc_link *link,
>>>> @@ -896,7 +952,11 @@ enum dc_edid_status dm_helpers_read_local_edid(
>>>>         * do check sum and retry to make sure read correct edid.
>>>>         */
>>>>        do {
>>>> -        drm_edid = drm_edid_read_ddc(connector, ddc);
>>>> +        drm_edid = dm_helpers_read_acpi_edid(aconnector);
>>>> +        if (drm_edid)
>>>> +            DRM_DEBUG_KMS("Using ACPI provided EDID for %s\n",
>>>> connector->name);
>>>
>>> It is better to always output a message when ACPI's EDID is used without
>>> enabling any debug options. How about DRM_INFO?
>>
>> Thanks, DRM_INFO makes sense for discoverability and will adjust it.
> 
> I'd suggest using dev_info() or one of the newer DRM macros so we know
> which device we are talking about if there are multiple GPUs in the
> system.

Ya, I'd personally prefer moving amdgpu_dm over to the new(er) drm_.*
family of logging macros.

> 
> Alex
> 
>>
>>>
>>>> +        else
>>>> +            drm_edid = drm_edid_read_ddc(connector, ddc);
>>>>            drm_edid_connector_update(connector, drm_edid);
>>>>            aconnector->drm_edid = drm_edid;
>>>> diff --git a/drivers/gpu/drm/amd/include/amd_shared.h
>>>> b/drivers/gpu/drm/amd/include/amd_shared.h
>>>> index 3f91926a50e9..1ec7c5e5249e 100644
>>>> --- a/drivers/gpu/drm/amd/include/amd_shared.h
>>>> +++ b/drivers/gpu/drm/amd/include/amd_shared.h
>>>> @@ -337,6 +337,11 @@ enum DC_DEBUG_MASK {
>>>>         * @DC_FORCE_IPS_ENABLE: If set, force enable all IPS, all the
>>>> time.
>>>>         */
>>>>        DC_FORCE_IPS_ENABLE = 0x4000,
>>>> +    /**
>>>> +     * @DC_DISABLE_ACPI_EDID: If set, don't attempt to fetch EDID for
>>>> +     * eDP display from ACPI _DDC method.
>>>> +     */
>>>> +    DC_DISABLE_ACPI_EDID = 0x8000,
>>>>    };
>>>>    enum amd_dpm_forced_level;
>>
-- 
Hamza