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Date: Mon, 12 Feb 2024 15:16:54 -0600
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v5 1/3] drm: Add support to get EDID from ACPI
Content-Language: en-US
From: Mario Limonciello <mario.limonciello@amd.com>
To: amd-gfx@lists.freedesktop.org,
 "open list:DRM DRIVERS" <dri-devel@lists.freedesktop.org>
Cc: "open list:ACPI" <linux-acpi@vger.kernel.org>,
 open list <linux-kernel@vger.kernel.org>, Melissa Wen <mwen@igalia.com>,
 Mark Pearson <mpearson-lenovo@squebb.ca>
References: <20240211055011.3583-1-mario.limonciello@amd.com>
 <20240211055011.3583-2-mario.limonciello@amd.com>
 <08ced68d-99bc-4a5e-90e7-f6a4b4b20e93@amd.com>
In-Reply-To: <08ced68d-99bc-4a5e-90e7-f6a4b4b20e93@amd.com>
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On 2/12/2024 10:31, Mario Limonciello wrote:
> On 2/10/2024 23:50, Mario Limonciello 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.
>>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>> v1->v2:
>>   * Split code from previous amdgpu specific helper to generic drm 
>> helper.
>> v2->v3:
>>   * Add an extra select to fix a variety of randconfig errors found from
>>     LKP robot.
>> v3->v4:
>>   * Return struct drm_edid
>> v4->v5:
>>   * Rename to drm_edid_read_acpi
>>   * Drop selects
>> ---
>>   drivers/gpu/drm/Kconfig     |   7 +++
>>   drivers/gpu/drm/drm_edid.c  | 113 +++++++++++++++++++++++++++++++++---
>>   include/drm/drm_connector.h |   6 ++
>>   include/drm/drm_edid.h      |   1 +
>>   4 files changed, 119 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>> index 2520db0b776e..a49740c528b9 100644
>> --- a/drivers/gpu/drm/Kconfig
>> +++ b/drivers/gpu/drm/Kconfig
>> @@ -103,6 +103,13 @@ config DRM_KMS_HELPER
>>       help
>>         CRTC helpers for KMS drivers.
>> +config DRM_ACPI_HELPER
>> +    tristate "ACPI support in DRM"
>> +    depends on DRM
>> +    depends on (ACPI_VIDEO || ACPI_VIDEO=n)
>> +    help
>> +      ACPI helpers for DRM drivers.
>> +
> 
> Unfortunately in my wider testing this still fails with a few combinations.
> 
> This combination fails to link:
> 
> CONFIG_ACPI_VIDEO=m
> CONFIG_DRM_ACPI_HELPER=y
> CONFIG_DRM=y
> 
> This combination links but doesn't work because the IS_REACHABLE() fails 
> (-EOPNOTSUPP):
> 
> CONFIG_ACPI_VIDEO=m
> CONFIG_DRM_ACPI_HELPER=M
> CONFIG_DRM=y
> 
> I'm tempted to split off all of drm_edid to it's own module instead  of 
> CONFIG_DRM_ACPI_HELPER which has a depends on (ACPI_VIDEO || 
> ACPI_VIDEIO=n).
> 
> Or Daniel, any better ideas?

I've come up with a solution that undoes all the select mess in 
preceding patches.

This patch will be swapped around to

--- 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

I'll wait a little for any other feedback and then post the updated 
series.  None of the other patches change in any material way.

> 
>>   config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
>>           bool "Enable refcount backtrace history in the DP MST helpers"
>>       depends on STACKTRACE_SUPPORT
>> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
>> index 69c68804023f..096c278b6f66 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 +2189,62 @@ 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 */
>> +    if (IS_REACHABLE(CONFIG_DRM_ACPI_HELPER)) {
>> +        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 -EINVAL;
>> +        }
>> +    } else {
>> +        r = -EOPNOTSUPP;
>> +    }
>> +    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 +2678,8 @@ 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 +2687,50 @@ 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 +2815,11 @@ 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 +2831,18 @@ 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 518d1b8106c7..38b5e1b5c773 100644
>> --- a/include/drm/drm_edid.h
>> +++ b/include/drm/drm_edid.h
>> @@ -463,5 +463,6 @@ 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__ */
>