[PATCH] drm/amd: force min_input_signal to 0 on Framework AMD 13/16

[Mario Limonciello]

+Kieran

On 6/10/2024 14:26, Thomas Weißschuh wrote:
> The value of "min_input_signal" returned from ATIF on a Framework AMD 13
> is "12". This leads to a fairly bright minimum display backlight.
> 
> Introduce a quirk to override "min_input_signal" to "0" which leads to a
> much lower minimum brightness, which is still readable even in daylight.
> 
> Tested on a Framework AMD 13 BIOS 3.05 and Framework AMD 16.
> 
> Link: https://community.frame.work/t/25711/9
> Link: https://community.frame.work/t/47036
> Signed-off-by: Thomas Weißschuh <linux at weissschuh.net>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 35 ++++++++++++++++++++++++++++++++
>   1 file changed, 35 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index 7099ff9cf8c5..b481889f7491 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -25,6 +25,7 @@
>   #include <linux/pci.h>
>   #include <linux/acpi.h>
>   #include <linux/backlight.h>
> +#include <linux/dmi.h>
>   #include <linux/slab.h>
>   #include <linux/xarray.h>
>   #include <linux/power_supply.h>
> @@ -130,6 +131,35 @@ static struct amdgpu_acpi_priv {
>   	struct amdgpu_atcs atcs;
>   } amdgpu_acpi_priv;
>   
> +struct amdgpu_acpi_quirks {
> +	bool ignore_min_input_signal;
> +};
> +
> +static const struct dmi_system_id amdgpu_acpi_quirk_table[] = {
> +	{
> +		/* the Framework Laptop 13 (AMD Ryzen) and 16 (AMD Ryzen) */
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "Framework"),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "AMD Ryzen"),
> +			DMI_MATCH(DMI_PRODUCT_FAMILY, "Laptop"),
> +		},

Two problems I see:

1) This really "should" be fixed in the BIOS. I added Kieran to the 
thread for comments if that's viable.

2) IMO this is going to match too liberally across all potential 
Framework models.  If they introduce a refreshed motherboard for either 
product then the quirk would apply to both products when we don't know 
that such a deficiency would exist.

You can reference drivers/platform/x86/amd/pmc/pmc-quirks.c for what we 
used for a quirk that was matching against a single product and single 
BIOS.

But FWIW if that issue isn't fixed in the next BIOS I think we'll end up 
needing to tear out the BIOS string match and match just the platform.


> +		.driver_data = &(struct amdgpu_acpi_quirks) {
> +			.ignore_min_input_signal = true,
> +		},
> +	},
> +	{}
> +};
> +
> +static const struct amdgpu_acpi_quirks *amdgpu_acpi_get_quirks(void)
> +{
> +	const struct dmi_system_id *dmi_id;
> +
> +	dmi_id = dmi_first_match(amdgpu_acpi_quirk_table);
> +	if (!dmi_id)
> +		return NULL;
> +	return dmi_id->driver_data;
> +}
> +
>   /* Call the ATIF method
>    */
>   /**
> @@ -1388,6 +1418,7 @@ bool amdgpu_acpi_should_gpu_reset(struct amdgpu_device *adev)
>    */
>   void amdgpu_acpi_detect(void)
>   {
> +	const struct amdgpu_acpi_quirks *quirks = amdgpu_acpi_get_quirks();
>   	struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
>   	struct amdgpu_atcs *atcs = &amdgpu_acpi_priv.atcs;
>   	struct pci_dev *pdev = NULL;
> @@ -1429,6 +1460,10 @@ void amdgpu_acpi_detect(void)
>   					ret);
>   			atif->backlight_caps.caps_valid = false;
>   		}
> +		if (quirks && quirks->ignore_min_input_signal) {
> +			DRM_INFO("amdgpu_acpi quirk: min_input_signal=0\n");
> +			atif->backlight_caps.min_input_signal = 0;
> +		}
>   	} else {
>   		atif->backlight_caps.caps_valid = false;
>   	}
> 
> ---
> base-commit: 83a7eefedc9b56fe7bfeff13b6c7356688ffa670
> change-id: 20240610-amdgpu-min-backlight-quirk-8402fd8e736a
> 
> Best regards,