[PATCH] drm/nouveau/agp: add a quirk list to limit agp modes

[Robert Hancock]

On 10/27/2013 09:54 AM, Ilia Mirkin wrote:
> Certain combinations of hardware can't actually support the maximum
> detected speed. Add a quirk list that lists pairs of hostbridge/chip pci
> ids and the mode that they should work with.
>
> See https://bugs.freedesktop.org/show_bug.cgi?id=20341

It seems like this quirk is likely too specific. This almost certainly 
affects more than 5600 Ultra cards and probably not just NV cards 
either. It probably affects more VIA chipsets than this too.

Given the amount of breakage that seems to exist with VIA AGP chipsets, 
I would think that being much more aggressive and forcing AGP mode to 2X 
maximum at the AGP driver level for all VIA chipsets doesn't seem like 
it would be a bad idea.

>
> Reported-by: Jason Detring <detringj at gmail.com>
> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
> ---
>
> I didn't go as far as subdevice matching... IMO that's overkill for now.
>
>   drivers/gpu/drm/nouveau/nouveau_agp.c | 44 +++++++++++++++++++++++++++++++----
>   1 file changed, 39 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_agp.c b/drivers/gpu/drm/nouveau/nouveau_agp.c
> index 6e7a55f..2953c4e 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_agp.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_agp.c
> @@ -11,10 +11,28 @@ MODULE_PARM_DESC(agpmode, "AGP mode (0 to disable AGP)");
>   static int nouveau_agpmode = -1;
>   module_param_named(agpmode, nouveau_agpmode, int, 0400);
>
> +struct nouveau_agpmode_quirk {
> +	u16 hostbridge_vendor;
> +	u16 hostbridge_device;
> +	u16 chip_vendor;
> +	u16 chip_device;
> +	int mode;
> +};
> +
> +static struct nouveau_agpmode_quirk nouveau_agpmode_quirk_list[] = {
> +	/* VIA Apollo PRO133x / GeForce FX 5600 Ultra, max agpmode 2, fdo #20341 */
> +	{ PCI_VENDOR_ID_VIA, 0x0691, PCI_VENDOR_ID_NVIDIA, 0x0311, 2 },
> +
> +	{},
> +};
> +
>   static unsigned long
> -get_agp_mode(struct nouveau_drm *drm, unsigned long mode)
> +get_agp_mode(struct nouveau_drm *drm, const struct drm_agp_info *info)
>   {
>   	struct nouveau_device *device = nv_device(drm->device);
> +	struct nouveau_agpmode_quirk *quirk = nouveau_agpmode_quirk_list;
> +	int agpmode = nouveau_agpmode;
> +	unsigned long mode = info->mode;
>
>   	/*
>   	 * FW seems to be broken on nv18, it makes the card lock up
> @@ -24,11 +42,27 @@ get_agp_mode(struct nouveau_drm *drm, unsigned long mode)
>   		mode &= ~PCI_AGP_COMMAND_FW;
>
>   	/*
> +	 * Go through the quirks list and adjust the agpmode accordingly.
> +	 */
> +	while (agpmode == -1 && quirk->hostbridge_vendor) {
> +		if (info->id_vendor == quirk->hostbridge_vendor &&
> +		    info->id_device == quirk->hostbridge_device &&
> +		    device->pdev->vendor == quirk->chip_vendor &&
> +		    device->pdev->device == quirk->chip_device) {
> +			agpmode = quirk->mode;
> +			nv_info(device, "Forcing agp mode to %dX. Use agpmode to override.\n",
> +				agpmode);
> +			break;
> +		}
> +		++quirk;
> +	}
> +
> +	/*
>   	 * AGP mode set in the command line.
>   	 */
> -	if (nouveau_agpmode > 0) {
> +	if (agpmode > 0) {
>   		bool agpv3 = mode & 0x8;
> -		int rate = agpv3 ? nouveau_agpmode / 4 : nouveau_agpmode;
> +		int rate = agpv3 ? agpmode / 4 : agpmode;
>
>   		mode = (mode & ~0x7) | (rate & 0x7);
>   	}
> @@ -90,7 +124,7 @@ nouveau_agp_reset(struct nouveau_drm *drm)
>   		if (ret)
>   			return;
>
> -		mode.mode  = get_agp_mode(drm, info.mode);
> +		mode.mode  = get_agp_mode(drm, &info);
>   		mode.mode &= ~PCI_AGP_COMMAND_FW;
>
>   		ret = drm_agp_enable(dev, mode);
> @@ -139,7 +173,7 @@ nouveau_agp_init(struct nouveau_drm *drm)
>   	}
>
>   	/* see agp.h for the AGPSTAT_* modes available */
> -	mode.mode = get_agp_mode(drm, info.mode);
> +	mode.mode = get_agp_mode(drm, &info);
>
>   	ret = drm_agp_enable(dev, mode);
>   	if (ret) {
>