| Message ID | 20240312154834.26178-2-tzimmermann@suse.de |
|---|---|
| State | Superseded |
| Headers | show |
| Series | drm: Provide fbdev emulation per memory manager | expand |
Thomas Zimmermann <tzimmermann@suse.de> writes: Hello Thomas, > Framebuffer memory is allocated via vmalloc() from non-contiguous It's vmalloc() true, but through vzmalloc() so I would mention that function instead in the commit message. > physical pages. The physical framebuffer start address is therefore > meaningless. Do not set it. > > The value is not used within the kernel and only exported to userspace > on dedicated ARM configs. No functional change is expected. > How's that info used? Does user-space assumes that the whole memory range is contiguous in physical memory or just cares about the phyisical start address ? > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") > Cc: Thomas Zimmermann <tzimmermann@suse.de> > Cc: Javier Martinez Canillas <javierm@redhat.com> > Cc: Zack Rusin <zackr@vmware.com> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > Cc: Maxime Ripard <mripard@kernel.org> > Cc: <stable@vger.kernel.org> # v6.4+ > --- > drivers/gpu/drm/drm_fbdev_generic.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c > index d647d89764cb9..b4659cd6285ab 100644 > --- a/drivers/gpu/drm/drm_fbdev_generic.c > +++ b/drivers/gpu/drm/drm_fbdev_generic.c > @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper, > /* screen */ > info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST; > info->screen_buffer = screen_buffer; > - info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer)); > info->fix.smem_len = screen_size; > Makes sense: Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> What about drivers/gpu/drm/drm_fb_helper.c btw? Since the memory range allocated may not be physically contiguous if a platform uses an IOMMU ? Asking because I don't really know how these exported values are used... I just know that is when the CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM is enabled. -- Best regards, Javier Martinez Canillas Core Platforms Red Hat
On Tue, Mar 12, 2024 at 11:48 AM Thomas Zimmermann <tzimmermann@suse.de> wrote: > > Framebuffer memory is allocated via vmalloc() from non-contiguous > physical pages. The physical framebuffer start address is therefore > meaningless. Do not set it. > > The value is not used within the kernel and only exported to userspace > on dedicated ARM configs. No functional change is expected. > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") > Cc: Thomas Zimmermann <tzimmermann@suse.de> > Cc: Javier Martinez Canillas <javierm@redhat.com> > Cc: Zack Rusin <zackr@vmware.com> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > Cc: Maxime Ripard <mripard@kernel.org> > Cc: <stable@vger.kernel.org> # v6.4+ > --- > drivers/gpu/drm/drm_fbdev_generic.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c > index d647d89764cb9..b4659cd6285ab 100644 > --- a/drivers/gpu/drm/drm_fbdev_generic.c > +++ b/drivers/gpu/drm/drm_fbdev_generic.c > @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper, > /* screen */ > info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST; > info->screen_buffer = screen_buffer; > - info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer)); > info->fix.smem_len = screen_size; > > /* deferred I/O */ > -- > 2.44.0 > Good idea. I think given that drm_leak_fbdev_smem is off by default we could remove the setting of smem_start by all of the in-tree drm drivers (they all have open source userspace that won't mess around with fbdev fb) - it will be reset to 0 anyway. Actually, I wonder if we still need drm_leak_fbdev_smem at all... Reviewed-by: Zack Rusin <zack.rusin@broadcom.com> z
Hi Am 18.03.24 um 03:35 schrieb Zack Rusin: > On Tue, Mar 12, 2024 at 11:48 AM Thomas Zimmermann <tzimmermann@suse.de> wrote: >> Framebuffer memory is allocated via vmalloc() from non-contiguous >> physical pages. The physical framebuffer start address is therefore >> meaningless. Do not set it. >> >> The value is not used within the kernel and only exported to userspace >> on dedicated ARM configs. No functional change is expected. >> >> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> >> Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") >> Cc: Thomas Zimmermann <tzimmermann@suse.de> >> Cc: Javier Martinez Canillas <javierm@redhat.com> >> Cc: Zack Rusin <zackr@vmware.com> >> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> >> Cc: Maxime Ripard <mripard@kernel.org> >> Cc: <stable@vger.kernel.org> # v6.4+ >> --- >> drivers/gpu/drm/drm_fbdev_generic.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c >> index d647d89764cb9..b4659cd6285ab 100644 >> --- a/drivers/gpu/drm/drm_fbdev_generic.c >> +++ b/drivers/gpu/drm/drm_fbdev_generic.c >> @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper, >> /* screen */ >> info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST; >> info->screen_buffer = screen_buffer; >> - info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer)); >> info->fix.smem_len = screen_size; >> >> /* deferred I/O */ >> -- >> 2.44.0 >> > Good idea. I think given that drm_leak_fbdev_smem is off by default we > could remove the setting of smem_start by all of the in-tree drm > drivers (they all have open source userspace that won't mess around > with fbdev fb) - it will be reset to 0 anyway. Actually, I wonder if > we still need drm_leak_fbdev_smem at all... All I know is that there's an embedded userspace driver that requires that setting. I don't even know which hardware. Best regards Thomas > > Reviewed-by: Zack Rusin <zack.rusin@broadcom.com> > > z
Hi Am 17.03.24 um 13:43 schrieb Javier Martinez Canillas: > Thomas Zimmermann <tzimmermann@suse.de> writes: > > Hello Thomas, > >> Framebuffer memory is allocated via vmalloc() from non-contiguous > It's vmalloc() true, but through vzmalloc() so I would mention that > function instead in the commit message. Ok. > >> physical pages. The physical framebuffer start address is therefore >> meaningless. Do not set it. >> >> The value is not used within the kernel and only exported to userspace >> on dedicated ARM configs. No functional change is expected. >> > How's that info used? Does user-space assumes that the whole memory range > is contiguous in physical memory or just cares about the phyisical start > address ? I assume that it is supposed to refer to contiguous memory. There's the corresponding field smem_len, which refers to the full memory. > >> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> >> Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") >> Cc: Thomas Zimmermann <tzimmermann@suse.de> >> Cc: Javier Martinez Canillas <javierm@redhat.com> >> Cc: Zack Rusin <zackr@vmware.com> >> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> >> Cc: Maxime Ripard <mripard@kernel.org> >> Cc: <stable@vger.kernel.org> # v6.4+ >> --- >> drivers/gpu/drm/drm_fbdev_generic.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c >> index d647d89764cb9..b4659cd6285ab 100644 >> --- a/drivers/gpu/drm/drm_fbdev_generic.c >> +++ b/drivers/gpu/drm/drm_fbdev_generic.c >> @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper, >> /* screen */ >> info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST; >> info->screen_buffer = screen_buffer; >> - info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer)); >> info->fix.smem_len = screen_size; >> > Makes sense: > > Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> > > What about drivers/gpu/drm/drm_fb_helper.c btw? Since the memory range > allocated may not be physically contiguous if a platform uses an IOMMU ? > > Asking because I don't really know how these exported values are used... > I just know that is when the CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM is enabled. The value of smem_start is used in the fbdev code in only two places : deferred I/O [1] and devfile I/O [2]. For the former, patch 5 of this series adds an additional test. The latter case is only relevant for framebuffers in I/O memory space. But that does not affect fbdev-generic, which has the shadow buffer in main memory. Some driver-internal fbdev code sets smem_length, such as in gma500, but these drivers are special anyway. For what userspace does with this value IDK. But it can't be much, as we've had smem_start cleared for years. Best regards Thomas [1] https://elixir.bootlin.com/linux/v6.8/source/drivers/video/fbdev/core/fb_defio.c#L34 [2] https://elixir.bootlin.com/linux/v6.8/source/drivers/video/fbdev/core/fb_io_fops.c#L143 > > -- > Best regards, > > Javier Martinez Canillas > Core Platforms > Red Hat > >
On Mon, Mar 18, 2024 at 08:59:01AM +0100, Thomas Zimmermann wrote: > Hi > > Am 18.03.24 um 03:35 schrieb Zack Rusin: > > On Tue, Mar 12, 2024 at 11:48 AM Thomas Zimmermann <tzimmermann@suse.de> wrote: > > > Framebuffer memory is allocated via vmalloc() from non-contiguous > > > physical pages. The physical framebuffer start address is therefore > > > meaningless. Do not set it. > > > > > > The value is not used within the kernel and only exported to userspace > > > on dedicated ARM configs. No functional change is expected. > > > > > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > > > Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") > > > Cc: Thomas Zimmermann <tzimmermann@suse.de> > > > Cc: Javier Martinez Canillas <javierm@redhat.com> > > > Cc: Zack Rusin <zackr@vmware.com> > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > > > Cc: Maxime Ripard <mripard@kernel.org> > > > Cc: <stable@vger.kernel.org> # v6.4+ > > > --- > > > drivers/gpu/drm/drm_fbdev_generic.c | 1 - > > > 1 file changed, 1 deletion(-) > > > > > > diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c > > > index d647d89764cb9..b4659cd6285ab 100644 > > > --- a/drivers/gpu/drm/drm_fbdev_generic.c > > > +++ b/drivers/gpu/drm/drm_fbdev_generic.c > > > @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper, > > > /* screen */ > > > info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST; > > > info->screen_buffer = screen_buffer; > > > - info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer)); > > > info->fix.smem_len = screen_size; > > > > > > /* deferred I/O */ > > > -- > > > 2.44.0 > > > > > Good idea. I think given that drm_leak_fbdev_smem is off by default we > > could remove the setting of smem_start by all of the in-tree drm > > drivers (they all have open source userspace that won't mess around > > with fbdev fb) - it will be reset to 0 anyway. Actually, I wonder if > > we still need drm_leak_fbdev_smem at all... > > All I know is that there's an embedded userspace driver that requires that > setting. I don't even know which hardware. The original Mali driver (ie, lima) used to require it, that's why we introduced it in the past. I'm not sure if the newer versions of that driver, or if newer Mali generations (ie, panfrost and panthor) closed source driver would require it, so it might be worth removing if it's easy enough to revert. Maxime
Maxime Ripard <mripard@kernel.org> writes: > On Mon, Mar 18, 2024 at 08:59:01AM +0100, Thomas Zimmermann wrote: >> Hi >> >> Am 18.03.24 um 03:35 schrieb Zack Rusin: >> > On Tue, Mar 12, 2024 at 11:48 AM Thomas Zimmermann <tzimmermann@suse.de> wrote: >> > > Framebuffer memory is allocated via vmalloc() from non-contiguous >> > > physical pages. The physical framebuffer start address is therefore >> > > meaningless. Do not set it. >> > > >> > > The value is not used within the kernel and only exported to userspace >> > > on dedicated ARM configs. No functional change is expected. >> > > >> > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> >> > > Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") >> > > Cc: Thomas Zimmermann <tzimmermann@suse.de> >> > > Cc: Javier Martinez Canillas <javierm@redhat.com> >> > > Cc: Zack Rusin <zackr@vmware.com> >> > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> >> > > Cc: Maxime Ripard <mripard@kernel.org> >> > > Cc: <stable@vger.kernel.org> # v6.4+ >> > > --- >> > > drivers/gpu/drm/drm_fbdev_generic.c | 1 - >> > > 1 file changed, 1 deletion(-) >> > > >> > > diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c >> > > index d647d89764cb9..b4659cd6285ab 100644 >> > > --- a/drivers/gpu/drm/drm_fbdev_generic.c >> > > +++ b/drivers/gpu/drm/drm_fbdev_generic.c >> > > @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper, >> > > /* screen */ >> > > info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST; >> > > info->screen_buffer = screen_buffer; >> > > - info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer)); >> > > info->fix.smem_len = screen_size; >> > > >> > > /* deferred I/O */ >> > > -- >> > > 2.44.0 >> > > >> > Good idea. I think given that drm_leak_fbdev_smem is off by default we >> > could remove the setting of smem_start by all of the in-tree drm >> > drivers (they all have open source userspace that won't mess around >> > with fbdev fb) - it will be reset to 0 anyway. Actually, I wonder if >> > we still need drm_leak_fbdev_smem at all... >> >> All I know is that there's an embedded userspace driver that requires that >> setting. I don't even know which hardware. > > The original Mali driver (ie, lima) used to require it, that's why we > introduced it in the past. > > I'm not sure if the newer versions of that driver, or if newer Mali > generations (ie, panfrost and panthor) closed source driver would > require it, so it might be worth removing if it's easy enough to revert. > Agreed. The DRM_FBDEV_LEAK_PHYS_SMEM symbol already depends on EXPERT and defaults to 'n', which implies that isn't enabled by most kernels AFAICT. So dropping it and see if anyone complains sounds like a good idea to me. > Maxime
Hi, On 2024/3/12 23:44, Thomas Zimmermann wrote: > Framebuffer memory is allocated via vmalloc() from non-contiguous > physical pages. The physical framebuffer start address is therefore > meaningless. Do not set it. > > The value is not used within the kernel and only exported to userspace > on dedicated ARM configs. No functional change is expected. > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") > Cc: Thomas Zimmermann <tzimmermann@suse.de> > Cc: Javier Martinez Canillas <javierm@redhat.com> > Cc: Zack Rusin <zackr@vmware.com> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > Cc: Maxime Ripard <mripard@kernel.org> > Cc: <stable@vger.kernel.org> # v6.4+ > Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> > Reviewed-by: Zack Rusin <zack.rusin@broadcom.com> Reviewed-by: Sui Jingfeng <sui.jingfeng@linux.dev> Tested-by: Sui Jingfeng <sui.jingfeng@linux.dev>
diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c index d647d89764cb9..b4659cd6285ab 100644 --- a/drivers/gpu/drm/drm_fbdev_generic.c +++ b/drivers/gpu/drm/drm_fbdev_generic.c @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper, /* screen */ info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST; info->screen_buffer = screen_buffer; - info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer)); info->fix.smem_len = screen_size; /* deferred I/O */
Framebuffer memory is allocated via vmalloc() from non-contiguous physical pages. The physical framebuffer start address is therefore meaningless. Do not set it. The value is not used within the kernel and only exported to userspace on dedicated ARM configs. No functional change is expected. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Javier Martinez Canillas <javierm@redhat.com> Cc: Zack Rusin <zackr@vmware.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: <stable@vger.kernel.org> # v6.4+ --- drivers/gpu/drm/drm_fbdev_generic.c | 1 - 1 file changed, 1 deletion(-)