[PATCH V2 1/3] drm/xe: Move enable host l2 VRAM post MCR init

[Lucas De Marchi]

On Wed, Aug 14, 2024 at 03:26:12PM GMT, Tejas Upadhyay wrote:
>enable host l2 VRAM is reading MCR register thus
>should be moved after MCR init is done.

This commit message skips a lot of the details on what was discussed in
the other thread. Let's improve it and for future please be more verbose
in your commit messages. Suggestion:

	xe_gt_enable_host_l2_vram() is reading the XE2_GAMREQSTRM_CTRL register
	that is currently missing the MCR annotation. However, just adding the
	annotation doesn't work as this function is called before MCR handling
	is initialized in xe_gt_mcr_init().

	xe_gt_enable_host_l2_vram() is used to implement WA 16023588340 that
	needs to be done as early as possible during initialization in order
	to be effective since the MMIO writes impact it. In the failure
	scenario, driver would simply not be able to bind sucesfully.

	Moving xe_gt_enable_host_l2_vram() later, after MCR initialization is
	done, only incurs a few additional HW accesses, particularly when
	loading GuC for hwconfig. Binding/unbinding the driver 100 times in
	BMG still works so it should be ok to start handling the WA a little
	bit later. This is sufficient to allow adding the MCR annotation to
	XE2_GAMREQSTRM_CTRL.

>
>V2(Matt):
> - Reword commit message
>V1(Lucas):
> - Reorder patch and reorder flow of L2 VRAM enable
>
>Cc: Lucas De Marchi <lucas.demarchi at intel.com>
>Signed-off-by: Tejas Upadhyay <tejas.upadhyay at intel.com>

Matt Roper / Matthew Auld, do the paragraphs above capture
correctly the discussion we had in the previous version?

with that,

// Reviewed-by: Lucas De Marchi <lucas.demarchi at intel.com>

thanks
Lucas De Marchi

>---
> drivers/gpu/drm/xe/xe_gt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_gt.c b/drivers/gpu/drm/xe/xe_gt.c
>index 58895ed22f6e..238c7d1053f0 100644
>--- a/drivers/gpu/drm/xe/xe_gt.c
>+++ b/drivers/gpu/drm/xe/xe_gt.c
>@@ -557,7 +557,6 @@ int xe_gt_init_hwconfig(struct xe_gt *gt)
>
> 	xe_gt_mcr_init_early(gt);
> 	xe_pat_init(gt);
>-	xe_gt_enable_host_l2_vram(gt);
>
> 	err = xe_uc_init(&gt->uc);
> 	if (err)
>@@ -569,6 +568,7 @@ int xe_gt_init_hwconfig(struct xe_gt *gt)
>
> 	xe_gt_topology_init(gt);
> 	xe_gt_mcr_init(gt);
>+	xe_gt_enable_host_l2_vram(gt);
>
> out_fw:
> 	xe_force_wake_put(gt_to_fw(gt), XE_FW_GT);
>-- 
>2.25.1
>