[Nouveau] [PATCH 1/2] disp: activate dual link TMDS links only when possible

[Ilia Mirkin]

On Tue, Nov 3, 2015 at 7:02 PM, Ben Skeggs <skeggsb at gmail.com> wrote:
> On 11/04/2015 08:41 AM, Ilia Mirkin wrote:
>> From: Hauke Mehrtens <hauke at hauke-m.de>
>>
>> Without this patch a pixel clock rate above 165 MHz on a TMDS link is
>> assumed to be dual link. This is true for DVI, but not for HDMI. HDMI
>> supports no dual link, but it supports pixel clock rates above 165 MHz.
>> Only activate Dual Link mode when it is actual possible.
>>
>> Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>> ---
>>  drm/nouveau/nv50_display.c           | 8 ++++----
>>  drm/nouveau/nvkm/engine/disp/gf119.c | 2 +-
>>  drm/nouveau/nvkm/engine/disp/nv50.c  | 2 +-
>>  3 files changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/drm/nouveau/nv50_display.c b/drm/nouveau/nv50_display.c
>> index c053c50..93bcfdf 100644
>> --- a/drm/nouveau/nv50_display.c
>> +++ b/drm/nouveau/nv50_display.c
>> @@ -1961,10 +1961,10 @@ nv50_sor_mode_set(struct drm_encoder *encoder, struct drm_display_mode *umode,
>>       switch (nv_encoder->dcb->type) {
>>       case DCB_OUTPUT_TMDS:
>>               if (nv_encoder->dcb->sorconf.link & 1) {
>> -                     if (mode->clock < 165000)
>> -                             proto = 0x1;
>> -                     else
>> -                             proto = 0x5;
>> +                     proto = 0x1;
>> +                     if (mode->clock >= 165000 &&
>> +                         nv_encoder->dcb->duallink_possible)
>> +                             proto |= 0x4;
> This is a somewhat flaky condition, given that one could plug a
> single-link HDMI monitor into a duallink-capable TMDS connector.
>
> Still, it's an improvement :)

Yeah, FWIW I thought of that (for the second patch too). All this
stuff is pretty fragile. But... what are you gonna do. Is there some
other way of telling whether we're on HDMI or DVI?

>
>>               } else {
>>                       proto = 0x2;
>>               }
>> diff --git a/drm/nouveau/nvkm/engine/disp/gf119.c b/drm/nouveau/nvkm/engine/disp/gf119.c
>> index 186fd3a..8691b68 100644
>> --- a/drm/nouveau/nvkm/engine/disp/gf119.c
>> +++ b/drm/nouveau/nvkm/engine/disp/gf119.c
>> @@ -158,7 +158,7 @@ exec_clkcmp(struct nv50_disp *disp, int head, int id, u32 pclk, u32 *conf)
>>       switch (outp->info.type) {
>>       case DCB_OUTPUT_TMDS:
>>               *conf = (ctrl & 0x00000f00) >> 8;
>> -             if (pclk >= 165000)
>> +             if (pclk >= 165000 && outp->info.duallink_possible)
>>                       *conf |= 0x0100;
> I think it might be more robust to key this off the SOR protocol, rather
> than duplicating the condition above.

You mean disp->sor.lvdsconf? What do I do with that? Or did you have
something else in mind?

>
>>               break;
>>       case DCB_OUTPUT_LVDS:
>> diff --git a/drm/nouveau/nvkm/engine/disp/nv50.c b/drm/nouveau/nvkm/engine/disp/nv50.c
>> index 32e73a9..ceecd0e 100644
>> --- a/drm/nouveau/nvkm/engine/disp/nv50.c
>> +++ b/drm/nouveau/nvkm/engine/disp/nv50.c
>> @@ -391,7 +391,7 @@ exec_clkcmp(struct nv50_disp *disp, int head, int id, u32 pclk, u32 *conf)
>>               switch (outp->info.type) {
>>               case DCB_OUTPUT_TMDS:
>>                       *conf = (ctrl & 0x00000f00) >> 8;
>> -                     if (pclk >= 165000)
>> +                     if (pclk >= 165000 && outp->info.duallink_possible)
>>                               *conf |= 0x0100;
> Same here.
>
>>                       break;
>>               case DCB_OUTPUT_LVDS:
>>
>