Re: [PATCH v6] drm/radeon: fix internal display on iMac11,1 (RV770/DCE3.1)

On Mon, Aug 17, 2026 at 02:43:26AM +0200, Gilles Risch wrote:
> The Apple iMac11,1 (27-inch, Late 2009) uses a Mobility Radeon HD 4850
> (RV770/DCE3.1) with a 2560x1440 internal panel on an internal
> DisplayPort path. Without this fix the display stays dark under KMS.
> 
> This machine suffers from the same issue as iMac10,1 and iMac11,2:
> Apple routes the internal display through Link B of the DIG encoder
> instead of Link A. Add iMac11,1 to the existing DMI quirk and move
> the Apple-specific encoder assignment into its own block, independent
> of the DCE version check.
> 
> Additionally, the 2560x1440 panel requires RADEON_PLL_USE_FRAC_FB_DIV
> and ATOM_ENCODER_CMD_DP_VIDEO_ON, limited to iMac11,1 via dmi_match()
> to avoid affecting other boards.
> 
> Signed-off-by: Gilles Risch <[email protected]>

Reviewed-by: Lukas Wunner <[email protected]>

> Good morning,
> 
> this is v6 of the patch, rebased on top of amd-staging-drm-next
> (agd5f/linux).
> 
> There are no functional or code changes since v5.
> 
> Regarding Lukas Wunner's previous Reviewed-by (which was provided on v2),
> I have kept him in CC so he can confirm if his review still stands given
> the changes between v2 and v5.
> 
> Could you have a look at this when you have a spare moment?
> 
> Regards,
> Gilles
> 
> Changes in v6:
> - Rebased on amd-staging-drm-next (no functional/code changes since v5)
> ---

Put additional information like this below the three dashes
so that it's not committed to the git repo when the maintainer
applies your patch.

> -	if (ASIC_IS_DCE32(rdev)) {
> -		if (dmi_match(DMI_PRODUCT_NAME, "iMac10,1") ||
> -		    dmi_match(DMI_PRODUCT_NAME, "iMac11,2"))
> -			enc_idx = (dig->linkb) ? 1 : 0;
> -		else
> -			enc_idx = radeon_crtc->crtc_id;
> +	if (dmi_match(DMI_PRODUCT_NAME, "iMac10,1") ||
> +	    dmi_match(DMI_PRODUCT_NAME, "iMac11,1") ||
> +	    dmi_match(DMI_PRODUCT_NAME, "iMac11,2")) {
> +		enc_idx = (dig->linkb) ? 1 : 0;
> +		goto assigned;
> +	}

Nit:
If the number of dmi_match() calls exceeds one or two, for readability
it's usually a good idea to create a table and match against that with
dmi_check_system().

Thanks,

Lukas