Re: [PATCH v2] drm/radeon: fix internal display on iMac11, 1 (RV770/DCE3.1)

[Lukas Wunner <lukas@wunner.de>]

On Sat, May 16, 2026 at 11:24:21AM +0200, Gilles Risch wrote:
> The Apple iMac11,1 (late 2009) has an integrated ATI Mobility Radeon
> HD 4850 (RV770/M98L) with a 2560x1440 internal panel connected via an
> internal DisplayPort path. This machine suffers from a similar problem
> as the iMac10,1 (late 2009) and the iMac11,2 (mid 2010). Without this
> fix the display stays dark under KMS. Two issues are addressed:
> 
> 1. The RV770 implements DCE3.1 and not DCE3.2. ASIC_IS_DCE32() starts at
>    CHIP_RV730 which is newer than RV770, so the RV770 never matched the
>    DCE3.2 PLL and encoder logic. Introduce ASIC_IS_DCE31() starting at
>    CHIP_RV770 to fix this.
> 
> 2. Apple routed the internal display through Link B of the DIG encoder
>    instead of Link A, as observed in the kernel display connector log.
>    The same quirk already exists for iMac10,1 and iMac11,2 - iMac11,1
>    was simply missing from the list.

Not an expert in the radeon driver or AMD chip revisions, but if it
helps improve support for older Macs I'll be happy to offer my:

Reviewed-by: Lukas Wunner <lukas@wunner.de>

It's not immediately obvious that CHIP_RV770 precedes CHIP_RV730
in the enum and that hence ASIC_IS_DCE31() subsumes ASIC_IS_DCE32().

Thanks,

Lukas