Re: [PATCH v3 2/8] drm/ast: Only map cursor BOs during updates

[Thomas Zimmermann <tzimmermann@suse.de>]

[-- Attachment #1.1.1: Type: text/plain, Size: 7703 bytes --]



Am 11.12.20 um 11:18 schrieb Daniel Vetter:
> On Wed, Dec 09, 2020 at 03:25:21PM +0100, Thomas Zimmermann wrote:
>> The HW cursor's BO used to be mapped permanently into the kernel's
>> address space. GEM's vmap operation will be protected by locks, and
>> we don't want to lock the BO's for an indefinate period of time.
>>
>> Change the cursor code to map the HW BOs only during updates. The
>> vmap operation in VRAM helpers is cheap, as a once estabished mapping
>> is being reused until the BO actually moves. As the HW cursor BOs are
>> permanently pinned, they never move at all.
>>
>> v2:
>> 	* fix typos in commit description
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> Acked-by: Christian König <christian.koenig@amd.com>
> 
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> 
> Now there's a pretty big issue here though: We can't take dma_resv_lock in
> commit_tail, because of possible deadlocks on at least gpus that do real
> async rendering because of the dma_fences. Unfortunately my annotations
> patches got stuck a bit, I need to refresh them.
> 
> Rules are you can pin and unpin stuff in prepare/cleanup_plane, and also
> take dma_resv_lock there, but not in commit_tail in-between. So I think
> our vmap_local needs to loose the unconditional assert_locked and require
> either that or a pin count.

I guess my commit description is misleading when it speaks of updates. 
ast_cursor_blit() is actually called from the cursor plane's prepare_fb 
function. [1] The vmap code in ast_cursor_show() could be moved into 
blit() as well, I think.

I guess the clean solution is to integrate the cursor code with the 
modesetting code in ast_mode. From there, locks and mappings can be 
established in prepare_fb and the HW state can be updated in atomic_commit.

Best regards
Thomas

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/ast/ast_mode.c#n646

> -Daniel
> 
>> ---
>>   drivers/gpu/drm/ast/ast_cursor.c | 51 ++++++++++++++++++--------------
>>   drivers/gpu/drm/ast/ast_drv.h    |  2 --
>>   2 files changed, 28 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ast/ast_cursor.c b/drivers/gpu/drm/ast/ast_cursor.c
>> index 68bf3d33f1ed..fac1ee79c372 100644
>> --- a/drivers/gpu/drm/ast/ast_cursor.c
>> +++ b/drivers/gpu/drm/ast/ast_cursor.c
>> @@ -39,7 +39,6 @@ static void ast_cursor_fini(struct ast_private *ast)
>>   
>>   	for (i = 0; i < ARRAY_SIZE(ast->cursor.gbo); ++i) {
>>   		gbo = ast->cursor.gbo[i];
>> -		drm_gem_vram_vunmap(gbo, &ast->cursor.map[i]);
>>   		drm_gem_vram_unpin(gbo);
>>   		drm_gem_vram_put(gbo);
>>   	}
>> @@ -53,14 +52,13 @@ static void ast_cursor_release(struct drm_device *dev, void *ptr)
>>   }
>>   
>>   /*
>> - * Allocate cursor BOs and pins them at the end of VRAM.
>> + * Allocate cursor BOs and pin them at the end of VRAM.
>>    */
>>   int ast_cursor_init(struct ast_private *ast)
>>   {
>>   	struct drm_device *dev = &ast->base;
>>   	size_t size, i;
>>   	struct drm_gem_vram_object *gbo;
>> -	struct dma_buf_map map;
>>   	int ret;
>>   
>>   	size = roundup(AST_HWC_SIZE + AST_HWC_SIGNATURE_SIZE, PAGE_SIZE);
>> @@ -77,15 +75,7 @@ int ast_cursor_init(struct ast_private *ast)
>>   			drm_gem_vram_put(gbo);
>>   			goto err_drm_gem_vram_put;
>>   		}
>> -		ret = drm_gem_vram_vmap(gbo, &map);
>> -		if (ret) {
>> -			drm_gem_vram_unpin(gbo);
>> -			drm_gem_vram_put(gbo);
>> -			goto err_drm_gem_vram_put;
>> -		}
>> -
>>   		ast->cursor.gbo[i] = gbo;
>> -		ast->cursor.map[i] = map;
>>   	}
>>   
>>   	return drmm_add_action_or_reset(dev, ast_cursor_release, NULL);
>> @@ -94,7 +84,6 @@ int ast_cursor_init(struct ast_private *ast)
>>   	while (i) {
>>   		--i;
>>   		gbo = ast->cursor.gbo[i];
>> -		drm_gem_vram_vunmap(gbo, &ast->cursor.map[i]);
>>   		drm_gem_vram_unpin(gbo);
>>   		drm_gem_vram_put(gbo);
>>   	}
>> @@ -168,31 +157,38 @@ static void update_cursor_image(u8 __iomem *dst, const u8 *src, int width, int h
>>   int ast_cursor_blit(struct ast_private *ast, struct drm_framebuffer *fb)
>>   {
>>   	struct drm_device *dev = &ast->base;
>> -	struct drm_gem_vram_object *gbo;
>> -	struct dma_buf_map map;
>> -	int ret;
>> -	void *src;
>> +	struct drm_gem_vram_object *dst_gbo = ast->cursor.gbo[ast->cursor.next_index];
>> +	struct drm_gem_vram_object *src_gbo = drm_gem_vram_of_gem(fb->obj[0]);
>> +	struct dma_buf_map src_map, dst_map;
>>   	void __iomem *dst;
>> +	void *src;
>> +	int ret;
>>   
>>   	if (drm_WARN_ON_ONCE(dev, fb->width > AST_MAX_HWC_WIDTH) ||
>>   	    drm_WARN_ON_ONCE(dev, fb->height > AST_MAX_HWC_HEIGHT))
>>   		return -EINVAL;
>>   
>> -	gbo = drm_gem_vram_of_gem(fb->obj[0]);
>> -
>> -	ret = drm_gem_vram_vmap(gbo, &map);
>> +	ret = drm_gem_vram_vmap(src_gbo, &src_map);
>>   	if (ret)
>>   		return ret;
>> -	src = map.vaddr; /* TODO: Use mapping abstraction properly */
>> +	src = src_map.vaddr; /* TODO: Use mapping abstraction properly */
>>   
>> -	dst = ast->cursor.map[ast->cursor.next_index].vaddr_iomem;
>> +	ret = drm_gem_vram_vmap(dst_gbo, &dst_map);
>> +	if (ret)
>> +		goto err_drm_gem_vram_vunmap;
>> +	dst = dst_map.vaddr_iomem; /* TODO: Use mapping abstraction properly */
>>   
>>   	/* do data transfer to cursor BO */
>>   	update_cursor_image(dst, src, fb->width, fb->height);
>>   
>> -	drm_gem_vram_vunmap(gbo, &map);
>> +	drm_gem_vram_vunmap(dst_gbo, &dst_map);
>> +	drm_gem_vram_vunmap(src_gbo, &src_map);
>>   
>>   	return 0;
>> +
>> +err_drm_gem_vram_vunmap:
>> +	drm_gem_vram_vunmap(src_gbo, &src_map);
>> +	return ret;
>>   }
>>   
>>   static void ast_cursor_set_base(struct ast_private *ast, u64 address)
>> @@ -243,17 +239,26 @@ static void ast_cursor_set_location(struct ast_private *ast, u16 x, u16 y,
>>   void ast_cursor_show(struct ast_private *ast, int x, int y,
>>   		     unsigned int offset_x, unsigned int offset_y)
>>   {
>> +	struct drm_device *dev = &ast->base;
>> +	struct drm_gem_vram_object *gbo = ast->cursor.gbo[ast->cursor.next_index];
>> +	struct dma_buf_map map;
>>   	u8 x_offset, y_offset;
>>   	u8 __iomem *dst;
>>   	u8 __iomem *sig;
>>   	u8 jreg;
>> +	int ret;
>>   
>> -	dst = ast->cursor.map[ast->cursor.next_index].vaddr;
>> +	ret = drm_gem_vram_vmap(gbo, &map);
>> +	if (drm_WARN_ONCE(dev, ret, "drm_gem_vram_vmap() failed, ret=%d\n", ret))
>> +		return;
>> +	dst = map.vaddr_iomem; /* TODO: Use mapping abstraction properly */
>>   
>>   	sig = dst + AST_HWC_SIZE;
>>   	writel(x, sig + AST_HWC_SIGNATURE_X);
>>   	writel(y, sig + AST_HWC_SIGNATURE_Y);
>>   
>> +	drm_gem_vram_vunmap(gbo, &map);
>> +
>>   	if (x < 0) {
>>   		x_offset = (-x) + offset_x;
>>   		x = 0;
>> diff --git a/drivers/gpu/drm/ast/ast_drv.h b/drivers/gpu/drm/ast/ast_drv.h
>> index ccaff81924ee..f871fc36c2f7 100644
>> --- a/drivers/gpu/drm/ast/ast_drv.h
>> +++ b/drivers/gpu/drm/ast/ast_drv.h
>> @@ -28,7 +28,6 @@
>>   #ifndef __AST_DRV_H__
>>   #define __AST_DRV_H__
>>   
>> -#include <linux/dma-buf-map.h>
>>   #include <linux/i2c.h>
>>   #include <linux/i2c-algo-bit.h>
>>   #include <linux/io.h>
>> @@ -133,7 +132,6 @@ struct ast_private {
>>   
>>   	struct {
>>   		struct drm_gem_vram_object *gbo[AST_DEFAULT_HWC_NUM];
>> -		struct dma_buf_map map[AST_DEFAULT_HWC_NUM];
>>   		unsigned int next_index;
>>   	} cursor;
>>   
>> -- 
>> 2.29.2
>>
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer


[-- Attachment #1.2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 840 bytes --]

[-- Attachment #2: Type: text/plain, Size: 183 bytes --]

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization