Re: [PATCH v2] x86: sysfb: remove sysfb when probing real hw

From: David Herrmann
Date: Wed Dec 18 2013 - 09:15:54 EST

Hi Pavel

On Wed, Dec 18, 2013 at 2:50 PM, David Herrmann <dh.herrmann@xxxxxxxxx> wrote:
> With CONFIG_X86_SYSFB=y, probing real hw-drivers may result in
> resource-conflicts and drivers will refuse to load. A call to
> request_mem_region() will fail, if the region overlaps with the mem-region
> used by simplefb. The common desktop DRM drivers (intel, nouveau, radeon)
> are not affected as they don't reserve their resources, but some others
> do, including (nvidiafb, cirrus, ..).
>
> The problem is that we add an IORESOURCE_MEM to the simple-framebuffer
> platform-device during bootup but never release it. Probing simplefb on
> this platform-device is fine, but the handover to real-hw via
> remove_conflicting_framebuffers() will only unload the fbdev driver, but
> keep the platform-device around. Thus, if the real hw-driver calls
> request_mem_region() and friends on the same PCI region, we will get a
> resource conflict and most drivers refuse to load. Users will see
> errors like:
> "nvidiafb: cannot reserve video memory at <xyz>"
>
> vesafb and efifb don't store any resources, so disabling CONFIG_X86_SYSFB
> and falling back to those drivers will avoid the bug. With sysfb enabled,
> we need to properly unload the simple-framebuffer devices before probing
> real hw-drivers.
>
> This patch adds sysfb_unregister() for that purpose. It can be called from
> any context (except from the platform-device ->probe and ->remove callback
> path), synchronously unloads any global sysfb and prevents new sysfbs from
> getting registered. Thus, you can call it even before any sysfb has been
> loaded. Note that for now we only do that for simple-framebuffer devices,
> as efi/vesa-framebuffer platform-drivers lack ->remove() callbacks.
> They're not affected by the resource-conflicts, so we can fix those later.
>
> This also changes remove_conflicting_framebuffer() to call this helper
> *before* trying its heuristic to remove conflicting drivers. This way, we
> unload sysfbs properly on any conflict. But to avoid dead-locks in
> register_framebuffer(), we must not call sysfb_unregister() for
> framebuffers probing on sysfb devices. Hence, we simply remove any
> aperture from simplefb and we're good to go. simplefb is unregistered by
> sysfb_unregister() now, so no reason to keep the apertures (on non-x86,
> there currently is no handover from simplefb, so we're fine. If it's
> added, they need to provide something like sysfb_unregister() too)

As you reported issues regarding nvidiafb, can you give this a try, too?

Thanks
David

> Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
> ---
> v2:
> - remove simplefb apertures to avoid dead-lock
> - skip sysfb_unregister() if no apertures are set
> - merge sysfb_alloc() into sysfb_register()
> - simplify sysfb_unregister() logic
> - call sysfb_unregister() even if SYSFB=n but X86=y
>
> Tested with efifb and simplefb + i915 handover on x86.
>
> Thanks
> David
>
> arch/x86/include/asm/sysfb.h | 6 ++++
> arch/x86/kernel/sysfb.c | 63 ++++++++++++++++++++++++++++++++++++++++
> arch/x86/kernel/sysfb_simplefb.c | 9 ++----
> drivers/video/fbmem.c | 19 ++++++++++++
> drivers/video/simplefb.c | 8 -----
> 5 files changed, 90 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/include/asm/sysfb.h b/arch/x86/include/asm/sysfb.h
> index 2aeb3e2..10d719d 100644
> --- a/arch/x86/include/asm/sysfb.h
> +++ b/arch/x86/include/asm/sysfb.h
> @@ -11,6 +11,7 @@
> * any later version.
> */
>
> +#include <linux/fb.h>
> #include <linux/kernel.h>
> #include <linux/platform_data/simplefb.h>
> #include <linux/screen_info.h>
> @@ -59,6 +60,11 @@ struct efifb_dmi_info {
> int flags;
> };
>
> +__init int sysfb_register(const char *name, int id,
> + const struct resource *res, unsigned int res_num,
> + const void *data, size_t data_size);
> +void sysfb_unregister(const struct apertures_struct *apert, bool primary);
> +
> #ifdef CONFIG_EFI
>
> extern struct efifb_dmi_info efifb_dmi_list[];
> diff --git a/arch/x86/kernel/sysfb.c b/arch/x86/kernel/sysfb.c
> index 193ec2c..9d8da8d 100644
> --- a/arch/x86/kernel/sysfb.c
> +++ b/arch/x86/kernel/sysfb.c
> @@ -33,11 +33,74 @@
> #include <linux/init.h>
> #include <linux/kernel.h>
> #include <linux/mm.h>
> +#include <linux/mutex.h>
> #include <linux/platform_data/simplefb.h>
> #include <linux/platform_device.h>
> #include <linux/screen_info.h>
> #include <asm/sysfb.h>
>
> +static DEFINE_MUTEX(sysfb_lock);
> +static struct platform_device *sysfb_dev;
> +
> +__init int sysfb_register(const char *name, int id,
> + const struct resource *res, unsigned int res_num,
> + const void *data, size_t data_size)
> +{
> + struct platform_device *pd;
> + int ret = 0;
> +
> + mutex_lock(&sysfb_lock);
> + if (!sysfb_dev) {
> + pd = platform_device_register_resndata(NULL, name, id,
> + res, res_num,
> + data, data_size);
> + if (IS_ERR(pd))
> + ret = PTR_ERR(pd);
> + else
> + sysfb_dev = pd;
> + }
> + mutex_unlock(&sysfb_lock);
> +
> + return ret;
> +}
> +
> +static bool sysfb_match(const struct apertures_struct *apert, bool primary)
> +{
> + struct screen_info *si = &screen_info;
> + unsigned int i;
> + const struct aperture *a;
> +
> + if (!apert || primary)
> + return true;
> +
> + for (i = 0; i < apert->count; ++i) {
> + a = &apert->ranges[i];
> + if (a->base >= si->lfb_base &&
> + a->base < si->lfb_base + ((u64)si->lfb_size << 16))
> + return true;
> + if (si->lfb_base >= a->base &&
> + si->lfb_base < a->base + a->size)
> + return true;
> + }
> +
> + return false;
> +}
> +
> +/* unregister the sysfb and prevent new sysfbs from getting registered */
> +void sysfb_unregister(const struct apertures_struct *apert, bool primary)
> +{
> + mutex_lock(&sysfb_lock);
> + if (!IS_ERR(sysfb_dev) && sysfb_dev) {
> + if (sysfb_match(apert, primary)) {
> + platform_device_unregister(sysfb_dev);
> + sysfb_dev = ERR_PTR(-EALREADY);
> + }
> + } else {
> + sysfb_dev = ERR_PTR(-EALREADY);
> + }
> + mutex_unlock(&sysfb_lock);
> +}
> +
> static __init int sysfb_init(void)
> {
> struct screen_info *si = &screen_info;
> diff --git a/arch/x86/kernel/sysfb_simplefb.c b/arch/x86/kernel/sysfb_simplefb.c
> index 86179d4..a760d47 100644
> --- a/arch/x86/kernel/sysfb_simplefb.c
> +++ b/arch/x86/kernel/sysfb_simplefb.c
> @@ -64,7 +64,6 @@ __init bool parse_mode(const struct screen_info *si,
> __init int create_simplefb(const struct screen_info *si,
> const struct simplefb_platform_data *mode)
> {
> - struct platform_device *pd;
> struct resource res;
> unsigned long len;
>
> @@ -86,10 +85,6 @@ __init int create_simplefb(const struct screen_info *si,
> if (res.end <= res.start)
> return -EINVAL;
>
> - pd = platform_device_register_resndata(NULL, "simple-framebuffer", 0,
> - &res, 1, mode, sizeof(*mode));
> - if (IS_ERR(pd))
> - return PTR_ERR(pd);
> -
> - return 0;
> + return sysfb_register("simple-framebuffer", 0, &res, 1, mode,
> + sizeof(*mode));
> }
> diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
> index 010d191..590a46a 100644
> --- a/drivers/video/fbmem.c
> +++ b/drivers/video/fbmem.c
> @@ -35,6 +35,9 @@
>
> #include <asm/fb.h>
>
> +#if IS_ENABLED(CONFIG_X86)
> +#include <asm/sysfb.h>
> +#endif
>
> /*
> * Frame buffer device initialization and setup routines
> @@ -1604,6 +1607,17 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
> }
> }
>
> +static void remove_conflicting_sysfb(const struct apertures_struct *apert,
> + bool primary)
> +{
> + if (!apert)
> + return;
> +
> +#if IS_ENABLED(CONFIG_X86)
> + sysfb_unregister(apert, primary);
> +#endif
> +}
> +
> static int do_register_framebuffer(struct fb_info *fb_info)
> {
> int i;
> @@ -1742,6 +1756,8 @@ EXPORT_SYMBOL(unlink_framebuffer);
> void remove_conflicting_framebuffers(struct apertures_struct *a,
> const char *name, bool primary)
> {
> + remove_conflicting_sysfb(a, primary);
> +
> mutex_lock(&registration_lock);
> do_remove_conflicting_framebuffers(a, name, primary);
> mutex_unlock(&registration_lock);
> @@ -1762,6 +1778,9 @@ register_framebuffer(struct fb_info *fb_info)
> {
> int ret;
>
> + remove_conflicting_sysfb(fb_info->apertures,
> + fb_is_primary_device(fb_info));
> +
> mutex_lock(&registration_lock);
> ret = do_register_framebuffer(fb_info);
> mutex_unlock(&registration_lock);
> diff --git a/drivers/video/simplefb.c b/drivers/video/simplefb.c
> index 210f3a0..9f4a0cf 100644
> --- a/drivers/video/simplefb.c
> +++ b/drivers/video/simplefb.c
> @@ -209,14 +209,6 @@ static int simplefb_probe(struct platform_device *pdev)
> info->var.blue = params.format->blue;
> info->var.transp = params.format->transp;
>
> - info->apertures = alloc_apertures(1);
> - if (!info->apertures) {
> - framebuffer_release(info);
> - return -ENOMEM;
> - }
> - info->apertures->ranges[0].base = info->fix.smem_start;
> - info->apertures->ranges[0].size = info->fix.smem_len;
> -
> info->fbops = &simplefb_ops;
> info->flags = FBINFO_DEFAULT | FBINFO_MISC_FIRMWARE;
> info->screen_base = ioremap_wc(info->fix.smem_start,
> --
> 1.8.5.1
>
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