[PATCH] drm/i915: Make sure dsm_size has correct granularity

[Lucas De Marchi]

On Thu, Feb 02, 2023 at 07:02:43PM +0100, Nirmoy Das wrote:
>DSM granularity is 1MB so make sure we stick to that.

I think we need to be a bit more verbose here, because in future we may
need to refer to this commit if/when things change (e.g. the granularity
or the additional size needed on top of DSM).

The issue this is fixing is that the address set by firmware in GEN12_DSMBASE
and read here doesn't mean "anything above it until the of lmem is part of DSM".
There may be a few KB that is not part of DSM. How large is that space
is platform-dependent, but since it's always less than the DSM
granularity, it can be simplified by simply aligning the size like
is done here.

>
>v2: replace "1 * SZ_1M" with SZ_1M (Andrzej).
>
>Cc: Matthew Auld <matthew.auld at intel.com>
>Suggested-by: Lucas De Marchi <lucas.demarchi at intel.com>
>Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
>Reviewed-by: Andrzej Hajda <andrzej.hajda at intel.com>


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

Are you ok with me amending the commit message and applying?

After this patch I think you can follow the process to request committer
access.

Lucas De Marchi

>---
> drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
>index 90a967374b1a..d8e06e783e30 100644
>--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
>+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
>@@ -909,7 +909,7 @@ i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
> 		dsm_base = intel_uncore_read64(uncore, GEN12_DSMBASE) & GEN12_BDSM_MASK;
> 		if (WARN_ON(lmem_size < dsm_base))
> 			return ERR_PTR(-ENODEV);
>-		dsm_size = lmem_size - dsm_base;
>+		dsm_size = ALIGN_DOWN(lmem_size - dsm_base, SZ_1M);
> 	}
>
> 	io_size = dsm_size;
>-- 
>2.39.0
>