Hot-unplug all firmware-framebuffer devices as part of removing them via remove_conflicting_framebuffers() et al. Releases all memory regions to be acquired by native drivers.

Firmware, such as EFI, install a framebuffer while posting the computer. After removing the firmware-framebuffer device from fbdev, a native driver takes over the hardware and the firmware framebuffer becomes invalid.

Firmware-framebuffer drivers, specifically simplefb, don't release their device from Linux' device hierarchy. It still owns the firmware framebuffer and blocks the native drivers from loading. This has been observed in the vmwgfx driver. [1]

Initiating a device removal (i.e., hot unplug) as part of remove_conflicting_framebuffers() removes the underlying device and returns the memory range to the system.

[1] https://lore.kernel.org/dri-devel/20220117180359.18114-1-zack@kde.org/

v2: * rename variable 'dev' to 'device' (Javier)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Reported-by: Zack Rusin zackr@vmware.com Reviewed-by: Javier Martinez Canillas javierm@redhat.com Reviewed-by: Zack Rusin zackr@vmware.com CC: stable@vger.kernel.org # v5.11+ --- drivers/video/fbdev/core/fbmem.c | 29 ++++++++++++++++++++++++++--- include/linux/fb.h | 1 + 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 0fa7ede94fa6..b585339509b0 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -25,6 +25,7 @@ #include <linux/init.h> #include <linux/linux_logo.h> #include <linux/proc_fs.h> +#include <linux/platform_device.h> #include <linux/seq_file.h> #include <linux/console.h> #include <linux/kmod.h> @@ -1557,18 +1558,36 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, /* check all firmware fbs and kick off if the base addr overlaps */ for_each_registered_fb(i) { struct apertures_struct *gen_aper; + struct device *device;

if (!(registered_fb[i]->flags & FBINFO_MISC_FIRMWARE)) continue;

gen_aper = registered_fb[i]->apertures; + device = registered_fb[i]->device; if (fb_do_apertures_overlap(gen_aper, a) || (primary && gen_aper && gen_aper->count && gen_aper->ranges[0].base == VGA_FB_PHYS)) {

printk(KERN_INFO "fb%d: switching to %s from %s\n", i, name, registered_fb[i]->fix.id); - do_unregister_framebuffer(registered_fb[i]); + + /* + * If we kick-out a firmware driver, we also want to remove + * the underlying platform device, such as simple-framebuffer, + * VESA, EFI, etc. A native driver will then be able to + * allocate the memory range. + * + * If it's not a platform device, at least print a warning. A + * fix would add code to remove the device from the system. + */ + if (dev_is_platform(device)) { + registered_fb[i]->forced_out = true; + platform_device_unregister(to_platform_device(device)); + } else { + pr_warn("fb%d: cannot remove device\n", i); + do_unregister_framebuffer(registered_fb[i]); + } } } } @@ -1898,9 +1917,13 @@ EXPORT_SYMBOL(register_framebuffer); void unregister_framebuffer(struct fb_info *fb_info) { - mutex_lock(&registration_lock); + bool forced_out = fb_info->forced_out; + + if (!forced_out) + mutex_lock(&registration_lock); do_unregister_framebuffer(fb_info); - mutex_unlock(&registration_lock); + if (!forced_out) + mutex_unlock(&registration_lock); } EXPORT_SYMBOL(unregister_framebuffer);

diff --git a/include/linux/fb.h b/include/linux/fb.h index 3da95842b207..9a14f3f8a329 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -502,6 +502,7 @@ struct fb_info { } *apertures;

bool skip_vt_switch; /* no VT switch on suspend/resume required */ + bool forced_out; /* set when being removed by another driver */ };

static inline struct apertures_struct *alloc_apertures(unsigned int max_num) {

Requesting the framebuffer memory in simpledrm marks the memory range as busy. This used to be done by the firmware sysfb code, but the driver is the correct place.

v2: * use I/O memory if request_mem_region() fails (Jocelyn)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Reviewed-by: Javier Martinez Canillas javierm@redhat.com --- drivers/gpu/drm/tiny/simpledrm.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c index 04146da2d1d8..d191e87a37b5 100644 --- a/drivers/gpu/drm/tiny/simpledrm.c +++ b/drivers/gpu/drm/tiny/simpledrm.c @@ -526,21 +526,33 @@ static int simpledrm_device_init_mm(struct simpledrm_device *sdev) { struct drm_device *dev = &sdev->dev; struct platform_device *pdev = sdev->pdev; - struct resource *mem; + struct resource *res, *mem; void __iomem *screen_base; int ret;

- mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); - if (!mem) + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + if (!res) return -EINVAL;

- ret = devm_aperture_acquire_from_firmware(dev, mem->start, resource_size(mem)); + ret = devm_aperture_acquire_from_firmware(dev, res->start, resource_size(res)); if (ret) { drm_err(dev, "could not acquire memory range %pr: error %d\n", - mem, ret); + res, ret); return ret; }

+ mem = devm_request_mem_region(&pdev->dev, res->start, resource_size(res), + sdev->dev.driver->name); + if (!mem) { + /* + * We cannot make this fatal. Sometimes this comes from magic + * spaces our resource handlers simply don't know about. Use + * the I/O-memory resource as-is and try to map that instead. + */ + drm_warn(dev, "could not acquire memory region %pr\n", res); + mem = res; + } + screen_base = devm_ioremap_wc(&pdev->dev, mem->start, resource_size(mem)); if (!screen_base)

Requesting the framebuffer memory in simpledrm marks the memory range as busy. This used to be done by the firmware sysfb code, but the driver is the correct place.

v2: * store memory region in struct for later cleanup (Javier)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de --- drivers/video/fbdev/simplefb.c | 65 +++++++++++++++++++++++----------- 1 file changed, 45 insertions(+), 20 deletions(-)

diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c index 57541887188b..94fc9c6d0411 100644 --- a/drivers/video/fbdev/simplefb.c +++ b/drivers/video/fbdev/simplefb.c @@ -66,16 +66,36 @@ static int simplefb_setcolreg(u_int regno, u_int red, u_int green, u_int blue, return 0; }

-struct simplefb_par; +struct simplefb_par { + u32 palette[PSEUDO_PALETTE_SIZE]; + struct resource *mem; +#if defined CONFIG_OF && defined CONFIG_COMMON_CLK + bool clks_enabled; + unsigned int clk_count; + struct clk **clks; +#endif +#if defined CONFIG_OF && defined CONFIG_REGULATOR + bool regulators_enabled; + u32 regulator_count; + struct regulator **regulators; +#endif +}; + static void simplefb_clocks_destroy(struct simplefb_par *par); static void simplefb_regulators_destroy(struct simplefb_par *par);

static void simplefb_destroy(struct fb_info *info) { + struct simplefb_par *par = info->par; + struct resource *mem = par->mem; + simplefb_regulators_destroy(info->par); simplefb_clocks_destroy(info->par); if (info->screen_base) iounmap(info->screen_base); + + if (mem) + release_mem_region(mem->start, resource_size(mem)); }

static const struct fb_ops simplefb_ops = { @@ -169,20 +189,6 @@ static int simplefb_parse_pd(struct platform_device *pdev, return 0; }

-struct simplefb_par { - u32 palette[PSEUDO_PALETTE_SIZE]; -#if defined CONFIG_OF && defined CONFIG_COMMON_CLK - bool clks_enabled; - unsigned int clk_count; - struct clk **clks; -#endif -#if defined CONFIG_OF && defined CONFIG_REGULATOR - bool regulators_enabled; - u32 regulator_count; - struct regulator **regulators; -#endif -}; - #if defined CONFIG_OF && defined CONFIG_COMMON_CLK /* * Clock handling code. @@ -405,7 +411,7 @@ static int simplefb_probe(struct platform_device *pdev) struct simplefb_params params; struct fb_info *info; struct simplefb_par *par; - struct resource *mem; + struct resource *res, *mem;

/* * Generic drivers must not be registered if a framebuffer exists. @@ -430,15 +436,28 @@ static int simplefb_probe(struct platform_device *pdev) if (ret) return ret;

- mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); - if (!mem) { + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + if (!res) { dev_err(&pdev->dev, "No memory resource\n"); return -EINVAL; }

+ mem = request_mem_region(res->start, resource_size(res), "simplefb"); + if (!mem) { + /* + * We cannot make this fatal. Sometimes this comes from magic + * spaces our resource handlers simply don't know about. Use + * the I/O-memory resource as-is and try to map that instead. + */ + dev_warn(&pdev->dev, "simplefb: cannot reserve video memory at %pR\n", res); + mem = res; + } + info = framebuffer_alloc(sizeof(struct simplefb_par), &pdev->dev); - if (!info) - return -ENOMEM; + if (!info) { + ret = -ENOMEM; + goto error_release_mem_region; + } platform_set_drvdata(pdev, info);

par = info->par; @@ -495,6 +514,9 @@ static int simplefb_probe(struct platform_device *pdev) info->var.xres, info->var.yres, info->var.bits_per_pixel, info->fix.line_length);

+ if (mem != res) + par->mem = mem; /* release in clean-up handler */ + ret = register_framebuffer(info); if (ret < 0) { dev_err(&pdev->dev, "Unable to register simplefb: %d\n", ret); @@ -513,6 +535,9 @@ static int simplefb_probe(struct platform_device *pdev) iounmap(info->screen_base); error_fb_release: framebuffer_release(info); +error_release_mem_region: + if (mem != res) + release_mem_region(mem->start, resource_size(mem)); return ret; }

Add a TODO item about requesting memory regions for each driver. The current DRM drivers don't do this consistently.

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Reviewed-by: Javier Martinez Canillas javierm@redhat.com --- Documentation/gpu/todo.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index da138dd39883..1b2372ef4131 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -467,6 +467,21 @@ Contact: Thomas Zimmermann tzimmermann@suse.de

Level: Intermediate

+Request memory regions in all drivers +------------------------------------- + +Go through all drivers and add code to request the memory regions that the +driver uses. This requires adding calls to request_mem_region(), +pci_request_region() or similar functions. Use helpers for managed cleanup +where possible. + +Drivers are pretty bad at doing this and there used to be conflicts among +DRM and fbdev drivers. Still, it's the correct thing to do. + +Contact: Thomas Zimmermann tzimmermann@suse.de + +Level: Starter +

Core refactorings =================