Re: [PATCH 6/8] drm/vram-helper: don't use ttm bo->offset v3

From: Nirmoy <nirmodas@amd.com>
To: Gerd Hoffmann <kraxel@redhat.com>, Nirmoy Das <nirmoy.aiemd@gmail.com>
Cc: thellstrom@vmware.com, amd-gfx@lists.freedesktop.org,
	airlied@linux.ie, kenny.ho@amd.com, brian.welty@intel.com,
	dri-devel@lists.freedesktop.org, nirmoy.das@amd.com,
	linux-graphics-maintainer@vmware.com, bskeggs@redhat.com,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	alexander.deucher@amd.com, sean@poorly.run,
	christian.koenig@amd.com
Subject: Re: [PATCH 6/8] drm/vram-helper: don't use ttm bo->offset v3
Date: Thu, 5 Mar 2020 15:35:57 +0100	[thread overview]
Message-ID: <3f6148c1-8357-0f18-3bda-bd989ac26393@amd.com> (raw)
In-Reply-To: <20200305140749.5oggp4gh6hozsh7j@sirius.home.kraxel.org>

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On 3/5/20 3:07 PM, Gerd Hoffmann wrote:
> On Thu, Mar 05, 2020 at 02:29:08PM +0100, Nirmoy Das wrote:
>> Calculate GEM VRAM bo's offset within vram-helper without depending on
>> bo->offset.
>>
>> Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>> ---
>>   drivers/gpu/drm/drm_gem_vram_helper.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
>> index 92a11bb42365..2749c2d25ac4 100644
>> --- a/drivers/gpu/drm/drm_gem_vram_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_vram_helper.c
>> @@ -198,6 +198,13 @@ u64 drm_gem_vram_mmap_offset(struct drm_gem_vram_object *gbo)
>>   }
>>   EXPORT_SYMBOL(drm_gem_vram_mmap_offset);
>>
>> +static s64 drm_gem_vram_pg_offset(struct drm_gem_vram_object *gbo)
>> +{
>> +	if (WARN_ON_ONCE(!gbo->bo.mem.mm_node))
>> +		return 0;
> returns 0 on error.

I am not sure if we should call this an error. This patch series removes 
below offset calculation from ttm_bo.c.

-	if (bo->mem.mm_node)
-		bo->offset = (bo->mem.start << PAGE_SHIFT) +
-		    bdev->man[bo->mem.mem_type].gpu_offset;
-	else
-		bo->offset = 0;
-

Most of the driver sets "bo->mem.mm_node". Thomas suggested to use this 
"return 0" in case some driver depends on bo->offset = 0.

>
>> +	return gbo->bo.mem.start;
>> +}
>> +
>>   /**
>>    * drm_gem_vram_offset() - \
>>   	Returns a GEM VRAM object's offset in video memory
>> @@ -214,7 +221,7 @@ s64 drm_gem_vram_offset(struct drm_gem_vram_object *gbo)
>>   {
>>   	if (WARN_ON_ONCE(!gbo->pin_count))
>>   		return (s64)-ENODEV;
> returns -errno on error.
>
>> -	return gbo->bo.offset;
>> +	return drm_gem_vram_pg_offset(gbo) << PAGE_SHIFT;
> And given that one calls the other behavior on error should better be
> consistent ...
>
> cheers,
>    Gerd
>

Regards,

Nirmoy

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