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

[Gilles Risch <gilles.risch@gmail.com>]

Good afternoon Lukas,

thanks for the review.

The initial launch date can either be verified in the TeraScale 
architecture comparison table on Wikipedia [1] or directly in the kernel 
source at drivers/gpu/drm/radeon/radeon_family.h where CHIP_RV770 (line 
74) precedes CHIP_RV730 (line 75).

The test robot mentions that it cannot find ASIC_IS_DCE31(); this is 
because both patches build on one another. Should I submit both patches 
as a series?

Kind regards,
Gilles

On 16.05.26 20:09, Lukas Wunner wrote:
> 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