Messages in this thread Patch in this message | | | Date | Mon, 13 Nov 2023 09:39:07 +0100 | Subject | Re: [PATCH] Fix failure of simpledrm probe when trying to grab FB from the EFI-based Framebuffer | From | Thomas Zimmermann <> |
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Hi Javier
Am 12.11.23 um 11:35 schrieb Javier Martinez Canillas: > Andrew Worsley <amworsley@gmail.com> writes: > > Hello Andrew, > >> On Sat, 11 Nov 2023 at 20:10, Javier Martinez Canillas >> <javierm@redhat.com> wrote: >>> >> .... >>>> On Sat, 11 Nov 2023 at 15:30, Andrew Worsley <amworsley@gmail.com> wrote: >>>>> >>>>> The simpledrm.c does not call aperture_remove_conflicting_devices() in it's probe >>>>> function as the drivers/video/aperture.c documentation says it should. Consequently >>>>> it's request for the FB memory fails. >>>>> >>> >>> The current behaviour is correct since aperture_remove_conflicting_devices() >>> is for native drivers to remove simple framebuffer devices such as simpledrm, >>> simplefb, efifb, etc. >> >> The efifb is the driver that has "grabbed" the FB earlier >> >> Here's a debug output with a dump_stack() call in the devm_aperture_acquire() >> % grep --color -A14 -B4 devm_aperture_acquire ~/dmesg2.txt >> [ 0.055752] efifb: framebuffer at 0xbd58dc000, using 16000k, total 16000k >> [ 0.055755] efifb: mode is 2560x1600x32, linelength=10240, pages=1 >> [ 0.055758] efifb: scrolling: redraw >> [ 0.055759] efifb: Truecolor: size=2:10:10:10, shift=30:20:10:0 >> [ 0.055771] devm_aperture_acquire: dump stack for debugging >> [ 0.055775] CPU: 2 PID: 1 Comm: swapper/0 Tainted: G S > > I see. This is the problem then. Your platform then is using a Device Tree > that contains a "simple-framebuffer" node but also doing a UEFI boot and > providing an EFI GOP table that is picked by the Linux EFI stub on boot. > > [...] > >>> >>>>> ... >>>>> [ 3.085302] simple-framebuffer bd58dc000.framebuffer: [drm] *ERROR* could not acquire memory range [??? 0xffff6e1d8629d580-0x2a5000001a7 flags 0x0]: -16 >>>>> [ 3.086433] simple-framebuffer: probe of bd58dc000.framebuffer failed with error -16 >>>>> ... >>>>> >>> >>> This is -EBUSY. What is your kernel configuration? Can you share it please. >> >> Attached - hope that's acceptable... >> >> > > Thanks a lot for providing this. It was very helpful to understand the issue. > > [...] > >>> >>> I would rather try to understand what is going on in your setup and why >>> the acquire is returning -EBUSY. >>> >> >> Ok - thanks - let me know where to go from here. >> > > I think that what we should do instead is to prevent both the EFI GOP and > "simple-framebuffer" to provide a system framebuffer information and the > kernel to register two devices (a "simple-framebuffer" by the OF core and > an "efi-framebuffer" by the sysfb infrastructure). > > In my opinion, the DTB is the best source of truth on an DT platform and > so is the sysfb that should be disabled if there's a "simple-framebuffer" > DT node found. > > Can you please try the following (untested) patch? > > From 7bf4a7917962c24c9f15aaf6e798db9d652c6806 Mon Sep 17 00:00:00 2001 > From: Javier Martinez Canillas <javierm@redhat.com> > Date: Sun, 12 Nov 2023 11:06:22 +0100 > Subject: [PATCH] of/platform: Disable sysfb if a simple-framebuffer node is > found > > Some DT platforms use EFI to boot and in this case the EFI Boot Services > may register a EFI_GRAPHICS_OUTPUT_PROTOCOL handle, that will later be > queried by the Linux EFI stub to fill the global struct screen_info data. > > The data is used by the Generic System Framebuffers (sysfb) framework to > add a platform device with platform data about the system framebuffer. > > But if there is a "simple-framebuffer" node in the DT, the OF core will > also do the same and add another device for the system framebuffer. > > This could lead for example, to two platform devices ("simple-framebuffer" > and "efi-framebuffer") to be added and matched with their corresponding > drivers. So both efifb and simpledrm will be probed, leading to following: > > [ 0.055752] efifb: framebuffer at 0xbd58dc000, using 16000k, total 16000k > [ 0.055755] efifb: mode is 2560x1600x32, linelength=10240, pages=1 > [ 0.055758] efifb: scrolling: redraw > [ 0.055759] efifb: Truecolor: size=2:10:10:10, shift=30:20:10:0 > ... > [ 3.295896] simple-framebuffer bd58dc000.framebuffer: [drm] *ERROR* > could not acquire memory range [??? 0xffff79f30a29ee40-0x2a5000001a7 > flags 0x0]: -16 > [ 3.298018] simple-framebuffer: probe of bd58dc000.framebuffer > failed with error -16 > > To prevent the issue, make the OF core to disable sysfb if there is a node > with a "simple-framebuffer" compatible. That way only this device will be > registered and sysfb would not attempt to register another one using the > screen_info data even if this has been filled. > > Reported-by: Andrew Worsley <amworsley@gmail.com> > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
It's a known problem and a know workaround. I don't find it particularly elegant, but have no other solution either. It would be much nicer to have a way for the sysfb code to detect whether it should create a device for the framebuffer.
Best regards Thomas
> --- > drivers/of/platform.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > index f235ab55b91e..a9fd91e6a6df 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -621,8 +621,21 @@ static int __init of_platform_default_populate_init(void) > } > > node = of_get_compatible_child(of_chosen, "simple-framebuffer"); > - of_platform_device_create(node, NULL, NULL); > - of_node_put(node); > + if (node) { > + /* > + * Since a "simple-framebuffer" device is already added > + * here, disable the Generic System Framebuffers (sysfb) > + * to prevent it from registering another device for the > + * system framebuffer later (e.g: using the screen_info > + * data that may had been filled as well). > + * > + * This can happen for example on DT systems that do EFI > + * booting and may provide a GOP table to the EFI stub. > + */ > + sysfb_disable(); > + of_platform_device_create(node, NULL, NULL); > + of_node_put(node); > + } > > /* Populate everything else. */ > of_platform_default_populate(NULL, NULL, NULL);
-- 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) [unhandled content-type:application/pgp-signature] | |