diff mbox series

[v2,21/43] drm/fbdev-dma: Implement damage handling and deferred I/O

Message ID 20240410130557.31572-22-tzimmermann@suse.de
State New
Headers show
Series drm: Provide fbdev emulation per memory manager | expand

Commit Message

Thomas Zimmermann April 10, 2024, 1:02 p.m. UTC
Add support for damage handling and deferred I/O to fbdev-dma. This
enables fbdev-dma to support all DMA-memory-based DRM drivers, even
such with a dirty callback in their framebuffers.

The patch adds the code for deferred I/O and also sets a dedicated
helper for struct fb_ops.fb_mmap that support coherent mappings.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_fbdev_dma.c | 65 ++++++++++++++++++++++++++-------
 1 file changed, 51 insertions(+), 14 deletions(-)

Comments

Javier Martinez Canillas April 16, 2024, 12:18 p.m. UTC | #1
Thomas Zimmermann <tzimmermann@suse.de> writes:

> Add support for damage handling and deferred I/O to fbdev-dma. This
> enables fbdev-dma to support all DMA-memory-based DRM drivers, even
> such with a dirty callback in their framebuffers.
>
> The patch adds the code for deferred I/O and also sets a dedicated
> helper for struct fb_ops.fb_mmap that support coherent mappings.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/drm_fbdev_dma.c | 65 ++++++++++++++++++++++++++-------
>  1 file changed, 51 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fbdev_dma.c b/drivers/gpu/drm/drm_fbdev_dma.c
> index 6c9427bb4053b..8ffd072368bca 100644
> --- a/drivers/gpu/drm/drm_fbdev_dma.c
> +++ b/drivers/gpu/drm/drm_fbdev_dma.c
> @@ -4,6 +4,7 @@
>  
>  #include <drm/drm_crtc_helper.h>
>  #include <drm/drm_drv.h>
> +#include <drm/drm_fb_dma_helper.h>
>  #include <drm/drm_fb_helper.h>
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_gem_dma_helper.h>
> @@ -35,6 +36,22 @@ static int drm_fbdev_dma_fb_release(struct fb_info *info, int user)
>  	return 0;
>  }
>  
> +FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(drm_fbdev_dma,
> +				   drm_fb_helper_damage_range,
> +				   drm_fb_helper_damage_area);
> +

Shouldn't this be FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS() instead ?

I know that right now the macros are the same but I believe that it was
added it for a reason ?

> +static int drm_fbdev_dma_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +	struct drm_framebuffer *fb = fb_helper->fb;
> +	struct drm_gem_dma_object *dma = drm_fb_dma_get_gem_obj(fb, 0);
> +
> +	if (!dma->map_noncoherent)
> +		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);

I noticed that some drivers do:

                 vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

I see that vm_get_page_prot() is a per-architecture function, but I don't
know about the implications of getting the pgprot_t from the vma->vm_flags
set or just using the current vma->vm_page_prot value...

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>

--
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat
Thomas Zimmermann April 16, 2024, 12:44 p.m. UTC | #2
Hi

Am 16.04.24 um 14:18 schrieb Javier Martinez Canillas:
> Thomas Zimmermann <tzimmermann@suse.de> writes:
>
>> Add support for damage handling and deferred I/O to fbdev-dma. This
>> enables fbdev-dma to support all DMA-memory-based DRM drivers, even
>> such with a dirty callback in their framebuffers.
>>
>> The patch adds the code for deferred I/O and also sets a dedicated
>> helper for struct fb_ops.fb_mmap that support coherent mappings.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> ---
>>   drivers/gpu/drm/drm_fbdev_dma.c | 65 ++++++++++++++++++++++++++-------
>>   1 file changed, 51 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_fbdev_dma.c b/drivers/gpu/drm/drm_fbdev_dma.c
>> index 6c9427bb4053b..8ffd072368bca 100644
>> --- a/drivers/gpu/drm/drm_fbdev_dma.c
>> +++ b/drivers/gpu/drm/drm_fbdev_dma.c
>> @@ -4,6 +4,7 @@
>>   
>>   #include <drm/drm_crtc_helper.h>
>>   #include <drm/drm_drv.h>
>> +#include <drm/drm_fb_dma_helper.h>
>>   #include <drm/drm_fb_helper.h>
>>   #include <drm/drm_framebuffer.h>
>>   #include <drm/drm_gem_dma_helper.h>
>> @@ -35,6 +36,22 @@ static int drm_fbdev_dma_fb_release(struct fb_info *info, int user)
>>   	return 0;
>>   }
>>   
>> +FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(drm_fbdev_dma,
>> +				   drm_fb_helper_damage_range,
>> +				   drm_fb_helper_damage_area);
>> +
> Shouldn't this be FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS() instead ?
>
> I know that right now the macros are the same but I believe that it was
> added it for a reason ?

Oh, thanks for noticing! I asked for that macro specifically for this 
reason. It went through the omap tree and hadn't arrived in 
drm-misc-next when I first made these patches. I'll update the patch 
accordingly.

>
>> +static int drm_fbdev_dma_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
>> +{
>> +	struct drm_fb_helper *fb_helper = info->par;
>> +	struct drm_framebuffer *fb = fb_helper->fb;
>> +	struct drm_gem_dma_object *dma = drm_fb_dma_get_gem_obj(fb, 0);
>> +
>> +	if (!dma->map_noncoherent)
>> +		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
> I noticed that some drivers do:
>
>                   vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
>
> I see that vm_get_page_prot() is a per-architecture function, but I don't
> know about the implications of getting the pgprot_t from the vma->vm_flags
> set or just using the current vma->vm_page_prot value...

That's in interesting observation. The code in the patch adds a WC flag 
to the existing vm_page_prot. The code in your example first creates a 
new vm_page_prot from the vm_flags field. Fbdev drivers generally use 
the former approach. So where does the original vm_page_prot value come 
from? (I think that's also the question behind your comment.)

I've looked through the kernel's mmap code from the syscall [1] to the 
place where it invokes the mmap callback. [2] Shortly before doing so, 
mmap_region() set's vm_page_prot from vm_flags like in your example. [3] 
I would assume there's no reason for drivers to call vm_get_page_prot() 
by themselves. DRM drivers specially seem to have the habit of doing so.

Best regards
Thomas

[1] 
https://elixir.bootlin.com/linux/v6.8/source/arch/x86/kernel/sys_x86_64.c#L86
[2] https://elixir.bootlin.com/linux/v6.8/source/mm/mmap.c#L2829
[3] https://elixir.bootlin.com/linux/v6.8/source/mm/mmap.c#L2824


>
> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
>
> --
> Best regards,
>
> Javier Martinez Canillas
> Core Platforms
> Red Hat
>
Javier Martinez Canillas April 16, 2024, 12:52 p.m. UTC | #3
Thomas Zimmermann <tzimmermann@suse.de> writes:

> Hi
>
> Am 16.04.24 um 14:18 schrieb Javier Martinez Canillas:
>> Thomas Zimmermann <tzimmermann@suse.de> writes:
>>

[...]

>>> +static int drm_fbdev_dma_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
>>> +{
>>> +	struct drm_fb_helper *fb_helper = info->par;
>>> +	struct drm_framebuffer *fb = fb_helper->fb;
>>> +	struct drm_gem_dma_object *dma = drm_fb_dma_get_gem_obj(fb, 0);
>>> +
>>> +	if (!dma->map_noncoherent)
>>> +		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
>> I noticed that some drivers do:
>>
>>                   vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
>>
>> I see that vm_get_page_prot() is a per-architecture function, but I don't
>> know about the implications of getting the pgprot_t from the vma->vm_flags
>> set or just using the current vma->vm_page_prot value...
>
> That's in interesting observation. The code in the patch adds a WC flag 
> to the existing vm_page_prot. The code in your example first creates a 
> new vm_page_prot from the vm_flags field. Fbdev drivers generally use 
> the former approach. So where does the original vm_page_prot value come 
> from? (I think that's also the question behind your comment.)
>

Yes, also if the vm_flags were set (and where) for this VMA.

> I've looked through the kernel's mmap code from the syscall [1] to the 
> place where it invokes the mmap callback. [2] Shortly before doing so, 
> mmap_region() set's vm_page_prot from vm_flags like in your example. [3] 
> I would assume there's no reason for drivers to call vm_get_page_prot() 
> by themselves. DRM drivers specially seem to have the habit of doing so.
>

Got it, makes sense. Thanks for taking a look.

> Best regards
> Thomas
>
diff mbox series

Patch

diff --git a/drivers/gpu/drm/drm_fbdev_dma.c b/drivers/gpu/drm/drm_fbdev_dma.c
index 6c9427bb4053b..8ffd072368bca 100644
--- a/drivers/gpu/drm/drm_fbdev_dma.c
+++ b/drivers/gpu/drm/drm_fbdev_dma.c
@@ -4,6 +4,7 @@ 
 
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_drv.h>
+#include <drm/drm_fb_dma_helper.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_dma_helper.h>
@@ -35,6 +36,22 @@  static int drm_fbdev_dma_fb_release(struct fb_info *info, int user)
 	return 0;
 }
 
+FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(drm_fbdev_dma,
+				   drm_fb_helper_damage_range,
+				   drm_fb_helper_damage_area);
+
+static int drm_fbdev_dma_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+	struct drm_framebuffer *fb = fb_helper->fb;
+	struct drm_gem_dma_object *dma = drm_fb_dma_get_gem_obj(fb, 0);
+
+	if (!dma->map_noncoherent)
+		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+
+	return fb_deferred_io_mmap(info, vma);
+}
+
 static void drm_fbdev_dma_fb_destroy(struct fb_info *info)
 {
 	struct drm_fb_helper *fb_helper = info->par;
@@ -51,20 +68,13 @@  static void drm_fbdev_dma_fb_destroy(struct fb_info *info)
 	kfree(fb_helper);
 }
 
-static int drm_fbdev_dma_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
-{
-	struct drm_fb_helper *fb_helper = info->par;
-
-	return drm_gem_prime_mmap(fb_helper->buffer->gem, vma);
-}
-
 static const struct fb_ops drm_fbdev_dma_fb_ops = {
 	.owner = THIS_MODULE,
 	.fb_open = drm_fbdev_dma_fb_open,
 	.fb_release = drm_fbdev_dma_fb_release,
-	__FB_DEFAULT_DMAMEM_OPS_RDWR,
+	__FB_DEFAULT_DEFERRED_OPS_RDWR(drm_fbdev_dma),
 	DRM_FB_HELPER_DEFAULT_OPS,
-	__FB_DEFAULT_DMAMEM_OPS_DRAW,
+	__FB_DEFAULT_DEFERRED_OPS_DRAW(drm_fbdev_dma),
 	.fb_mmap = drm_fbdev_dma_fb_mmap,
 	.fb_destroy = drm_fbdev_dma_fb_destroy,
 };
@@ -98,10 +108,6 @@  static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
 	dma_obj = to_drm_gem_dma_obj(buffer->gem);
 
 	fb = buffer->fb;
-	if (drm_WARN_ON(dev, fb->funcs->dirty)) {
-		ret = -ENODEV; /* damage handling not supported; use generic emulation */
-		goto err_drm_client_buffer_delete;
-	}
 
 	ret = drm_client_buffer_vmap(buffer, &map);
 	if (ret) {
@@ -112,7 +118,7 @@  static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
 	}
 
 	fb_helper->buffer = buffer;
-	fb_helper->fb = buffer->fb;
+	fb_helper->fb = fb;
 
 	info = drm_fb_helper_alloc_info(fb_helper);
 	if (IS_ERR(info)) {
@@ -133,8 +139,19 @@  static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
 	info->fix.smem_start = page_to_phys(virt_to_page(info->screen_buffer));
 	info->fix.smem_len = info->screen_size;
 
+	/* deferred I/O */
+	fb_helper->fbdefio.delay = HZ / 20;
+	fb_helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;
+
+	info->fbdefio = &fb_helper->fbdefio;
+	ret = fb_deferred_io_init(info);
+	if (ret)
+		goto err_drm_fb_helper_release_info;
+
 	return 0;
 
+err_drm_fb_helper_release_info:
+	drm_fb_helper_release_info(fb_helper);
 err_drm_client_buffer_vunmap:
 	fb_helper->fb = NULL;
 	fb_helper->buffer = NULL;
@@ -144,8 +161,28 @@  static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
 	return ret;
 }
 
+static int drm_fbdev_dma_helper_fb_dirty(struct drm_fb_helper *helper,
+					 struct drm_clip_rect *clip)
+{
+	struct drm_device *dev = helper->dev;
+	int ret;
+
+	/* Call damage handlers only if necessary */
+	if (!(clip->x1 < clip->x2 && clip->y1 < clip->y2))
+		return 0;
+
+	if (helper->fb->funcs->dirty) {
+		ret = helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, clip, 1);
+		if (drm_WARN_ONCE(dev, ret, "Dirty helper failed: ret=%d\n", ret))
+			return ret;
+	}
+
+	return 0;
+}
+
 static const struct drm_fb_helper_funcs drm_fbdev_dma_helper_funcs = {
 	.fb_probe = drm_fbdev_dma_helper_fb_probe,
+	.fb_dirty = drm_fbdev_dma_helper_fb_dirty,
 };
 
 /*