Re: drm/fbdev-dma: regression

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 11.11.24 um 14:42 schrieb Nuno Gonçalves:
> On Mon, Nov 11, 2024 at 1:22 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>> The patch in question changes the whole memory management of the
>> affected code. It's also noteworthy that most of it has been reworked
>> for the upcoming v6.12. Maybe this already fixed the problem. Kernel
>> v6.11-rc7 added commit 5a498d4d06d6 ("drm/fbdev-dma: Only install
>> deferred I/O if necessary"), which possibly fixes the problem as well.
>>
>> But there's no explicit fix for this problem and I have not seen any
>> other related reports. Any further information is welcome.
> Issue was present since 5ab91447aa13b8b98bc11f5326f33500b0ee2c48 and
> tested until 6.12-rc3.
> Is there any suggestion on how to dig down?

Here's a first attempt to address this bug. Could you please apply the 
attached patch and report on the results? It should work against the 
upcoming v6.13-rc1 or against a recent drm-misc-next.

Best regards
Thomas

>
> Thanks

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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From 40d481266497437ebaa5312c9af9641361b172f8 Mon Sep 17 00:00:00 2001
From: Thomas Zimmermann <tzimmermann@suse.de>
Date: Thu, 28 Nov 2024 14:25:03 +0100
Subject: [PATCH] fbdev-dma: Support deferred I/O without smem_start

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_fbdev_dma.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/gpu/drm/drm_fbdev_dma.c b/drivers/gpu/drm/drm_fbdev_dma.c
index b14b581c059d..6a94d1b62479 100644
--- a/drivers/gpu/drm/drm_fbdev_dma.c
+++ b/drivers/gpu/drm/drm_fbdev_dma.c
@@ -8,6 +8,7 @@
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_dma_helper.h>
+#include <drm/drm_gem_framebuffer_helper.h>
 
 /*
  * struct fb_ops
@@ -124,6 +125,28 @@ static const struct drm_fb_helper_funcs drm_fbdev_dma_helper_funcs = {
 	.fb_dirty = drm_fbdev_dma_helper_fb_dirty,
 };
 
+static struct page *drm_fbdev_dma_get_page(struct fb_info *info, unsigned long offset)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+	struct drm_framebuffer *fb = fb_helper->fb;
+	struct drm_gem_object *obj = drm_gem_fb_get_obj(fb, 0);
+	const void *addr = info->screen_buffer + offset;
+	struct page *page = NULL;
+
+	if (fb_WARN_ON_ONCE(info, offset > obj->size))
+		return NULL;
+
+	if (is_vmalloc_addr(addr))
+		page = vmalloc_to_page(addr);
+	else if (virt_addr_valid(addr))
+		page = virt_to_page(addr);
+
+	if (!fb_WARN_ON_ONCE(info, !page))
+		get_page(page);
+
+	return page;
+}
+
 /*
  * struct drm_fb_helper
  */
@@ -217,6 +240,7 @@ int drm_fbdev_dma_driver_fbdev_probe(struct drm_fb_helper *fb_helper,
 	/* deferred I/O */
 	if (use_deferred_io) {
 		fb_helper->fbdefio.delay = HZ / 20;
+		fb_helper->fbdefio.get_page = drm_fbdev_dma_get_page;
 		fb_helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;
 
 		info->fbdefio = &fb_helper->fbdefio;
-- 
2.47.0