linux-kernel - Re: [PATCH] drm: Permit video-buffers writecombine mapping for MIPS

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Date:   Tue, 18 Jun 2019 15:52:04 -0400
From:   Sean Paul <sean@...rly.run>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>,
        Junwei Zhang <Jerry.Zhang@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        dri-devel@...ts.freedesktop.org, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        "Vadim V . Vlasov" <vadim.vlasov@...latforms.ru>
Subject: Re: [PATCH] drm: Permit video-buffers writecombine mapping for MIPS

On Mon, Jun 17, 2019 at 04:47:30PM +0300, Serge Semin wrote:
> Hello folks,
> 
> Any updates of this patch status? It has been here for about two months.
> 

Sorry for the mixup, looks like this one just fell through the cracks. I've
applied it to drm-misc-next with the attached Ack and Review.

Sean


> Regards,
> -Sergey
> 
> On Tue, Apr 23, 2019 at 03:31:22PM +0300, Serge Semin wrote:
> > Since commit 4b050ba7a66c ("MIPS: pgtable.h: Implement the
> > pgprot_writecombine function for MIPS") and commit c4687b15a848 ("MIPS: Fix
> > definition of pgprot_writecombine()") write-combine vma mapping is
> > available to be used by kernel subsystems for MIPS. In particular the
> > uncached accelerated attribute is requested to be set by ioremap_wc()
> > method and by generic PCI memory pages/ranges mapping methods. The same
> > is done by the drm_io_prot()/ttm_io_prot() functions in case if
> > write-combine flag is set for vma's passed for mapping. But for some
> > reason the pgprot_writecombine() method calling is ifdefed to be a
> > platform-specific with MIPS system being marked as lacking of one. At the
> > very least it doesn't reflect the current MIPS platform implementation.
> > So in order to improve the DRM subsystem performance on MIPS with UCA
> > mapping enabled, we need to have pgprot_writecombine() called for buffers,
> > which need store operations being combined. In case if particular MIPS
> > chip doesn't support the UCA attribute, the mapping will fall back to
> > noncached.
> > 
> > Cc: Ralf Baechle <ralf@...ux-mips.org>
> > Cc: Paul Burton <paul.burton@...s.com>
> > Cc: James Hogan <jhogan@...nel.org>
> > Signed-off-by: Vadim V. Vlasov <vadim.vlasov@...latforms.ru>
> > Signed-off-by: Serge Semin <fancer.lancer@...il.com>
> > ---
> >  drivers/gpu/drm/drm_vm.c          | 5 +++--
> >  drivers/gpu/drm/ttm/ttm_bo_util.c | 4 ++--
> >  2 files changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
> > index c3301046dfaa..50178dc64060 100644
> > --- a/drivers/gpu/drm/drm_vm.c
> > +++ b/drivers/gpu/drm/drm_vm.c
> > @@ -62,7 +62,8 @@ static pgprot_t drm_io_prot(struct drm_local_map *map,
> >  	/* We don't want graphics memory to be mapped encrypted */
> >  	tmp = pgprot_decrypted(tmp);
> >  
> > -#if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__)
> > +#if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__) || \
> > +    defined(__mips__)
> >  	if (map->type == _DRM_REGISTERS && !(map->flags & _DRM_WRITE_COMBINING))
> >  		tmp = pgprot_noncached(tmp);
> >  	else
> > @@ -73,7 +74,7 @@ static pgprot_t drm_io_prot(struct drm_local_map *map,
> >  		tmp = pgprot_writecombine(tmp);
> >  	else
> >  		tmp = pgprot_noncached(tmp);
> > -#elif defined(__sparc__) || defined(__arm__) || defined(__mips__)
> > +#elif defined(__sparc__) || defined(__arm__)
> >  	tmp = pgprot_noncached(tmp);
> >  #endif
> >  	return tmp;
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> > index 895d77d799e4..9f918b992f7e 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> > @@ -539,13 +539,13 @@ pgprot_t ttm_io_prot(uint32_t caching_flags, pgprot_t tmp)
> >  		tmp = pgprot_noncached(tmp);
> >  #endif
> >  #if defined(__ia64__) || defined(__arm__) || defined(__aarch64__) || \
> > -    defined(__powerpc__)
> > +    defined(__powerpc__) || defined(__mips__)
> >  	if (caching_flags & TTM_PL_FLAG_WC)
> >  		tmp = pgprot_writecombine(tmp);
> >  	else
> >  		tmp = pgprot_noncached(tmp);
> >  #endif
> > -#if defined(__sparc__) || defined(__mips__)
> > +#if defined(__sparc__)
> >  	tmp = pgprot_noncached(tmp);
> >  #endif
> >  	return tmp;
> > -- 
> > 2.21.0
> > 

-- 
Sean Paul, Software Engineer, Google / Chromium OS