At Wed, 18 Dec 2013 09:44:35 +0100, Takashi Iwai wrote: > > At Wed, 18 Dec 2013 09:21:28 +0100, > David Herrmann wrote: > > > > Hi > > > > On Wed, Dec 18, 2013 at 8:42 AM, Takashi Iwai <tiwai@xxxxxxx> wrote: > > > Hi, > > > > > > with the recent enablement of simplefb on x86, cirrusdrmfb on QEMU/KVM > > > gets broken now, as reported at: > > > https://bugzilla.novell.com/show_bug.cgi?id=855821 > > > > > > The cirrus VGA resource is reserved at first as "BOOTFB" in > > > arch/x86/kernel/sysfb_simplefb.c, which is taken by simplefb platform > > > device. This resource is, however, never released until the platform > > > device is destroyed, and the framebuffer switching doesn't trigger > > > it. It calls fb's destroy callback, at most. Then, cirrus driver > > > tries to assign the resource, fails and gives up, resulting in a > > > complete blank screen. > > > > > > The same problem should exist on other KMS drivers like mgag200 or > > > ast, not only cirrus. Intel graphics doesn't hit this problem just > > > because the reserved iomem by BOOTFB isn't required by i915 driver. > > > > > > The patch below is a quick attempt to solve the issue. It adds a new > > > API function for releasing resources of platform_device, and call it > > > in destroy op of simplefb. But, forcibly releasing resources of a > > > parent device doesn't sound like a correct design. We may take such > > > as a band aid, but definitely need a more fundamental fix. > > > > > > Any thoughts? > > > > That bug always existed, simplefb is just the first driver to hit it > > (vesafb/efifb didn't use resources). > > Heh, the bug didn't "exist" because no other grabbed the resource > before. The way the cirrus driver allocates the resource is no bug, > per se. But the proper resource takeover is missing. > > > I'm aware of the issue but as a > > workaround you can simply disable CONFIG_X86_SYSFB. That restores the > > old behavior. > > Yes, but CONFIG_X86_SYSFB breaks things as of now. Shouldn't it be > mentioned or give some kconfig hints instead of silently giving a > broken output, if any quick fix isn't possible? > > > As a proper fix, I'd propose something like: > > dev = platform_find_device("platform-framebuffer"); > > platform_remove_device(dev); > > > > And we wrap this as: > > sysfb_remove_framebuffers() > > in arch/x86/kernel/sysfb.c > > > > This should cause a ->remove() event for the platform-driver and > > correctly release the resources. Comments? > > Who will call this? From destroy callback? > Or can we simply do put_device() the bound platform device instead? Just tested, put_device() doesn't work since the refcount isn't 1, so if any, we need to call platform_device_unregister() to release forcibly. The patch below seems working at a quick test. But I still have some bad feeling for unregistering the parent device from the child's destroy callback... thanks, Takashi --- diff --git a/drivers/video/simplefb.c b/drivers/video/simplefb.c index 210f3a02121a..196360c54157 100644 --- a/drivers/video/simplefb.c +++ b/drivers/video/simplefb.c @@ -41,6 +41,11 @@ static struct fb_var_screeninfo simplefb_var = { .vmode = FB_VMODE_NONINTERLACED, }; +struct simplefb_priv { + u32 pseudo_palette[16]; + struct platform_device *pdev; +}; + static int simplefb_setcolreg(u_int regno, u_int red, u_int green, u_int blue, u_int transp, struct fb_info *info) { @@ -68,8 +73,19 @@ static int simplefb_setcolreg(u_int regno, u_int red, u_int green, u_int blue, static void simplefb_destroy(struct fb_info *info) { + struct simplefb_priv *priv = info->par; + struct platform_device *pdev = priv->pdev; + if (info->screen_base) iounmap(info->screen_base); + + /* release the bound platform device when called from + * remove_conflicting_framebuffers() + */ + if (pdev) { + priv->pdev = NULL; /* to avoid double-free */ + platform_device_unregister(pdev); + } } static struct fb_ops simplefb_ops = { @@ -169,6 +185,7 @@ static int simplefb_probe(struct platform_device *pdev) struct simplefb_params params; struct fb_info *info; struct resource *mem; + struct simplefb_priv *priv; if (fb_get_options("simplefb", NULL)) return -ENODEV; @@ -188,7 +205,7 @@ static int simplefb_probe(struct platform_device *pdev) return -EINVAL; } - info = framebuffer_alloc(sizeof(u32) * 16, &pdev->dev); + info = framebuffer_alloc(sizeof(struct simplefb_priv), &pdev->dev); if (!info) return -ENOMEM; platform_set_drvdata(pdev, info); @@ -225,7 +242,9 @@ static int simplefb_probe(struct platform_device *pdev) framebuffer_release(info); return -ENODEV; } - info->pseudo_palette = (void *)(info + 1); + + priv = info->par; + info->pseudo_palette = priv->pseudo_palette; dev_info(&pdev->dev, "framebuffer at 0x%lx, 0x%x bytes, mapped to 0x%p\n", info->fix.smem_start, info->fix.smem_len, @@ -243,6 +262,7 @@ static int simplefb_probe(struct platform_device *pdev) return ret; } + priv->pdev = pdev; dev_info(&pdev->dev, "fb%d: simplefb registered!\n", info->node); return 0; @@ -251,8 +271,13 @@ static int simplefb_probe(struct platform_device *pdev) static int simplefb_remove(struct platform_device *pdev) { struct fb_info *info = platform_get_drvdata(pdev); + struct simplefb_priv *priv = info->par; + + if (priv->pdev) { + priv->pdev = NULL; /* to avoid double-free */ + unregister_framebuffer(info); + } - unregister_framebuffer(info); framebuffer_release(info); return 0; -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
