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

[Das, Nirmoy]

Hi Lucas,

On 2/3/2023 7:56 PM, Lucas De Marchi wrote:
> 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?


Yes, I fine that, thanks for doing that. I agree this is very short 
description that I have wrote.


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


Looking for to doing that :)


Nirmoy

>
> 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
>>