Re: cirrusdrmfb broken with simplefb
From: Takashi Iwai
Date: Wed Dec 18 2013 - 06:39:20 EST
At Wed, 18 Dec 2013 11:21:46 +0100,
David Herrmann wrote:
>
> Hi
>
> On Wed, Dec 18, 2013 at 11:17 AM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> > 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...
>
> The idea is right, but call it from
> "remove_conflicting_framebuffers()". The problem is, if we load a
> driver on top of a dummy like vesafb/efifb/simplefb, we never removed
> them properly. Instead, we only unregistered their fb driver. But with
> the driver-model, that's just removing the driver, not the dummy
> device.
>
> So we'd just call platform_device_unregister() in
> remove_conflicting_framebuffers() instead of unregister_framebuffer()
> on such devices. I'm now at home and will have a look.
So, make sysfb_remove_framebuffers() available on all archs and
call it there? Hmm... I think we need a better binding between
platform_device and framebuffer device. Maybe better than killing
a parent device, but IMO, the root cause is rather that we have two
individual devices (platform and framebuffer) unnecessarily. Can we
sort this out?
In anyway, the patch below is a quick revisited fix. It's calling
sysfb_remove_framebuffers(). Instead of finding over a platform name
string as you suggested, the patch just tries to remember the
instance.
The ifdef in fbmem.c looks ugly, but we can clean up such a thing
later. And, yes, the patch should be split.
thanks,
Takashi
---
diff --git a/arch/x86/include/asm/sysfb.h b/arch/x86/include/asm/sysfb.h
index 2aeb3e2..94ba0e4 100644
--- a/arch/x86/include/asm/sysfb.h
+++ b/arch/x86/include/asm/sysfb.h
@@ -76,8 +76,9 @@ static inline void sysfb_apply_efi_quirks(void)
bool parse_mode(const struct screen_info *si,
struct simplefb_platform_data *mode);
-int create_simplefb(const struct screen_info *si,
+struct platform_device *create_simplefb(const struct screen_info *si,
const struct simplefb_platform_data *mode);
+void sysfb_remove_framebuffers(void);
#else /* CONFIG_X86_SYSFB */
@@ -87,10 +88,10 @@ static inline bool parse_mode(const struct screen_info *si,
return false;
}
-static inline int create_simplefb(const struct screen_info *si,
+static inline struct platform_device *create_simplefb(const struct screen_info *si,
const struct simplefb_platform_data *mode)
{
- return -EINVAL;
+ return ERR_PTR(-EINVAL);
}
#endif /* CONFIG_X86_SYSFB */
diff --git a/arch/x86/kernel/sysfb.c b/arch/x86/kernel/sysfb.c
index 193ec2c..4faa5d0 100644
--- a/arch/x86/kernel/sysfb.c
+++ b/arch/x86/kernel/sysfb.c
@@ -38,23 +38,22 @@
#include <linux/screen_info.h>
#include <asm/sysfb.h>
+static struct platform_device *pd;
+
static __init int sysfb_init(void)
{
struct screen_info *si = &screen_info;
struct simplefb_platform_data mode;
- struct platform_device *pd;
const char *name;
bool compatible;
- int ret;
sysfb_apply_efi_quirks();
/* try to create a simple-framebuffer device */
compatible = parse_mode(si, &mode);
if (compatible) {
- ret = create_simplefb(si, &mode);
- if (!ret)
- return 0;
+ pd = create_simplefb(si, &mode);
+ return IS_ERR(pd) ? PTR_ERR(pd) : 0;
}
/* if the FB is incompatible, create a legacy framebuffer device */
@@ -70,5 +69,14 @@ static __init int sysfb_init(void)
return IS_ERR(pd) ? PTR_ERR(pd) : 0;
}
+void sysfb_remove_framebuffers(void)
+{
+ if (!IS_ERR_OR_NULL(pd)) {
+ platform_device_unregister(pd);
+ pd = NULL;
+ }
+}
+EXPORT_SYMBOL_GPL(sysfb_remove_framebuffers);
+
/* must execute after PCI subsystem for EFI quirks */
device_initcall(sysfb_init);
diff --git a/arch/x86/kernel/sysfb_simplefb.c b/arch/x86/kernel/sysfb_simplefb.c
index 86179d4..d90042ac 100644
--- a/arch/x86/kernel/sysfb_simplefb.c
+++ b/arch/x86/kernel/sysfb_simplefb.c
@@ -61,10 +61,9 @@ __init bool parse_mode(const struct screen_info *si,
return false;
}
-__init int create_simplefb(const struct screen_info *si,
+__init struct platform_device *create_simplefb(const struct screen_info *si,
const struct simplefb_platform_data *mode)
{
- struct platform_device *pd;
struct resource res;
unsigned long len;
@@ -74,7 +73,7 @@ __init int create_simplefb(const struct screen_info *si,
len = PAGE_ALIGN(len);
if (len > (u64)si->lfb_size << 16) {
printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
- return -EINVAL;
+ return ERR_PTR(-EINVAL);
}
/* setup IORESOURCE_MEM as framebuffer memory */
@@ -84,12 +83,8 @@ __init int create_simplefb(const struct screen_info *si,
res.start = si->lfb_base;
res.end = si->lfb_base + len - 1;
if (res.end <= res.start)
- return -EINVAL;
+ return ERR_PTR(-EINVAL);
- pd = platform_device_register_resndata(NULL, "simple-framebuffer", 0,
+ return platform_device_register_resndata(NULL, "simple-framebuffer", 0,
&res, 1, mode, sizeof(*mode));
- if (IS_ERR(pd))
- return PTR_ERR(pd);
-
- return 0;
}
diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 010d191..49b0f89 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -34,6 +34,9 @@
#include <linux/fb.h>
#include <asm/fb.h>
+#ifdef CONFIG_X86
+#include <asm/sysfb.h>
+#endif
/*
@@ -1600,6 +1603,9 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
"%s vs %s - removing generic driver\n",
name, registered_fb[i]->fix.id);
do_unregister_framebuffer(registered_fb[i]);
+#ifdef CONFIG_X86
+ sysfb_remove_framebuffers();
+#endif
}
}
}
diff --git a/drivers/video/simplefb.c b/drivers/video/simplefb.c
index 210f3a0..c825b88 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];
+ bool fb_registered;
+};
+
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 +73,11 @@ 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;
+
if (info->screen_base)
iounmap(info->screen_base);
+ priv->fb_registered = false;
}
static struct fb_ops simplefb_ops = {
@@ -169,6 +177,7 @@ 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 +197,7 @@ 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 +234,9 @@ 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 +254,7 @@ static int simplefb_probe(struct platform_device *pdev)
return ret;
}
+ priv->fb_registered = true;
dev_info(&pdev->dev, "fb%d: simplefb registered!\n", info->node);
return 0;
@@ -251,8 +263,11 @@ 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->fb_registered)
+ unregister_framebuffer(info);
- unregister_framebuffer(info);
framebuffer_release(info);
return 0;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/