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

[Ben Skeggs <skeggsb-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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On 11/04/2015 08:41 AM, Ilia Mirkin wrote:
> From: Hauke Mehrtens <hauke-5/S+JYg5SzeELgA04lAiVw@public.gmane.org>
> 
> 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-5/S+JYg5SzeELgA04lAiVw@public.gmane.org>
> Signed-off-by: Ilia Mirkin <imirkin-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org>
> ---
>  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 :)

>  		} 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.

>  		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:
> 


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