[PATCH] efifb: Fix runtime pm calls for non PCI efifb device

[Kai-Heng Feng]

Hi Sudeep,

On Tue, Apr 20, 2021 at 3:53 PM Sudeep Holla <sudeep.holla at arm.com> wrote:
>
> Gentle Ping! There is boot failure because of this issue with linux-next
> on few arm platforms with non PCIe efifb. Please review and get the fix
> merged ASAP so the testing on these platforms can continue with linux-next.

It was merged in drm-tip as d510c88cfbb2 ("efifb: Check efifb_pci_dev
before using it").

Kai-Heng

>
> On Thu, Apr 15, 2021 at 11:22:24AM +0100, Sudeep Holla wrote:
> > Commit a6c0fd3d5a8b ("efifb: Ensure graphics device for efifb stays at PCI D0")
> > added runtime pm calls to probe and remove routines to ensure the PCI
> > device for efifb stays in D0 state. However not ever efifb is based on
> > PCI device and efifb_pci_dev can be NULL if that is the case.
> >
> > In such cases, we will get a boot splat like below due to NULL dereference:
> > -->8
> >  Console: switching to colour frame buffer device 240x67
> >  fb0: EFI VGA frame buffer device
> >  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000270
> >  Mem abort info:
> >    ESR = 0x96000004
> >    EC = 0x25: DABT (current EL), IL = 32 bits
> >    SET = 0, FnV = 0
> >    EA = 0, S1PTW = 0
> >  Data abort info:
> >    ISV = 0, ISS = 0x00000004
> >    CM = 0, WnR = 0
> >  [0000000000000270] user address but active_mm is swapper
> >  Internal error: Oops: 96000004 [#1] PREEMPT SMP
> >  Modules linked in:
> >  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.12.0-rc7-next-20210413 #1
> >  Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform
> >  pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--)
> >  pc : pm_runtime_drop_link+0x12c/0x338
> >  lr : efifb_probe+0x7bc/0x7f0
> >  Call trace:
> >   pm_runtime_drop_link+0x12c/0x338
> >   efifb_probe+0x7bc/0x7f0
> >   platform_probe+0x68/0xd8
> >   really_probe+0xe4/0x3a8
> >   driver_probe_device+0x64/0xc8
> >   device_driver_attach+0x74/0x80
> >   __driver_attach+0x64/0xf0
> >   bus_for_each_dev+0x70/0xc0
> >   driver_attach+0x24/0x30
> >   bus_add_driver+0x150/0x1f8
> >   driver_register+0x64/0x120
> >   __platform_driver_register+0x28/0x38
> >   efifb_driver_init+0x1c/0x28
> >   do_one_initcall+0x48/0x2b0
> >   kernel_init_freeable+0x1e8/0x258
> >   kernel_init+0x14/0x118
> >   ret_from_fork+0x10/0x30
> >  Code: 88027c01 35ffffa2 17fff706 f9800051 (885f7c40)
> >  ---[ end trace 17d8da630bf8ff77 ]---
> >  Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> > -->8
> >
> > Fix the issue by checking for non-NULL efifb_pci_dev before dereferencing
> > for runtime pm calls in probe and remove routines.
> >
> > Fixes: a6c0fd3d5a8b ("efifb: Ensure graphics device for efifb stays at PCI D0")
> > Cc: Kai-Heng Feng <kai.heng.feng at canonical.com>
> > Cc: Alex Deucher <alexander.deucher at amd.com>
> > Cc: Thomas Zimmermann <tzimmermann at suse.de>
> > Cc: Peter Jones <pjones at redhat.com>
> > Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
> > ---
> >  drivers/video/fbdev/efifb.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> > index f58a545b3bf3..8ea8f079cde2 100644
> > --- a/drivers/video/fbdev/efifb.c
> > +++ b/drivers/video/fbdev/efifb.c
> > @@ -575,7 +575,8 @@ static int efifb_probe(struct platform_device *dev)
> >               goto err_fb_dealoc;
> >       }
> >       fb_info(info, "%s frame buffer device\n", info->fix.id);
> > -     pm_runtime_get_sync(&efifb_pci_dev->dev);
> > +     if (efifb_pci_dev)
> > +             pm_runtime_get_sync(&efifb_pci_dev->dev);
> >       return 0;
> >
> >  err_fb_dealoc:
> > @@ -602,7 +603,8 @@ static int efifb_remove(struct platform_device *pdev)
> >       unregister_framebuffer(info);
> >       sysfs_remove_groups(&pdev->dev.kobj, efifb_groups);
> >       framebuffer_release(info);
> > -     pm_runtime_put(&efifb_pci_dev->dev);
> > +     if (efifb_pci_dev)
> > +             pm_runtime_put(&efifb_pci_dev->dev);
> >
> >       return 0;
> >  }
> > --
> > 2.25.1
> >
>
> --
> Regards,
> Sudeep