[Intel-gfx] [PATCH] drm/vgem: Use 256B aligned pitch

[Daniel Vetter]

On Wed, Jun 30, 2021 at 12:46:27PM +0000, Surendrakumar Upadhyay, TejaskumarX wrote:
> 
> 
> > -----Original Message-----
> > From: Daniel Vetter <daniel at ffwll.ch>
> > Sent: 30 June 2021 17:52
> > To: Surendrakumar Upadhyay, TejaskumarX
> > <tejaskumarx.surendrakumar.upadhyay at intel.com>
> > Cc: dri-devel at lists.freedesktop.org; intel-gfx at lists.freedesktop.org;
> > chris at chris-wilson.co.uk
> > Subject: Re: [Intel-gfx] [PATCH] drm/vgem: Use 256B aligned pitch
> > 
> > On Wed, Jun 30, 2021 at 05:32:15PM +0530, Tejas Upadhyay wrote:
> > > Having different alignment requirement by different drivers, 256B
> > > aligned should work for all drm drivers.
> > 
> > What.
> > 
> > Like yes vgem abuses dumb_create, but it's not a kms driver. Pitch is
> > meaningless, and that's why we align it minimally to 1 byte (bpp = bits per
> > pixel here).
> > 
> > Maybe start with explaining what you're trying to do here.
> > -Daniel
> > >
> 
> Igt tool tests which are trying to exercise tests through VGEM are getting failure (if not 64B aligned) on Intel platforms in creating framebuffer as they need them to be 64B aligned. Then 64B alignment is not 
> A requirement for all drm drivers.

Fix the tests. We're not going to encode alignment constraints for all kms
drivers in vgem, that's not what vgem is for.

Really what we should have done is just give vgem an ioctl to allocate a
buffer, with the size specified in bytes. Not this "abuse dumb_create"
business we're doing. But that's a past mistake, can't really fix that.
-Daniel

> 
> Thanks,
> Tejas
> 
> > > Signed-off-by: Tejas Upadhyay
> > > <tejaskumarx.surendrakumar.upadhyay at intel.com>
> > > ---
> > >  drivers/gpu/drm/vgem/vgem_drv.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/vgem/vgem_drv.c
> > > b/drivers/gpu/drm/vgem/vgem_drv.c index bf38a7e319d1..1da6df5e256a
> > > 100644
> > > --- a/drivers/gpu/drm/vgem/vgem_drv.c
> > > +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> > > @@ -215,7 +215,7 @@ static int vgem_gem_dumb_create(struct drm_file
> > *file, struct drm_device *dev,
> > >  	struct drm_gem_object *gem_object;
> > >  	u64 pitch, size;
> > >
> > > -	pitch = args->width * DIV_ROUND_UP(args->bpp, 8);
> > > +	pitch = ALIGN(args->width * DIV_ROUND_UP(args->bpp, 8), 256);
> > >  	size = args->height * pitch;
> > >  	if (size == 0)
> > >  		return -EINVAL;
> > > --
> > > 2.31.1
> > >
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > 
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch