Hi Avri,
Thanks for your patch!
On Sun, 26 Jan 2025 at 07:48, Avri Altman <avri.altman@xxxxxxx> wrote:
> This commit addresses an issue where `clk_gating.state` is being toggled
> in `ufshcd_setup_clocks` even if clock gating is not allowed. This can
> lead to a crash with the following error:
>
> BUG: spinlock bad magic on CPU#6, swapper/0/1
> lock: 0xffffff84443014e8, .magic: 00000000, .owner: <none>/-1,
> .owner_cpu: 0
> CPU: 6 UID: 0 PID: 1 Comm: swapper/0 Not tainted
> 6.13.0-rcar3-initrd-08318-g75abbef32a94 #896
> Hardware name: R-Car S4 Starter Kit board (DT)
> Call trace:
> show_stack+0x18/0x24 (C)
> dump_stack_lvl+0x60/0x80
> dump_stack+0x18/0x24
> spin_bug+0x7c/0xa0
> do_raw_spin_lock+0x34/0xb4
> _raw_spin_lock_irqsave+0x1c/0x30
> class_spinlock_irqsave_constructor+0x18/0x30
> ufshcd_setup_clocks+0x98/0x23c
> ufshcd_init+0x288/0xd38
> ufshcd_pltfrm_init+0x618/0x738
> ufs_renesas_probe+0x18/0x24
> platform_probe+0x68/0xb8
> really_probe+0x138/0x268
> __driver_probe_device+0xf4/0x10c
> driver_probe_device+0x3c/0xf8
> __driver_attach+0xf0/0x100
> bus_for_each_dev+0x84/0xdc
> driver_attach+0x24/0x30
> bus_add_driver+0xe8/0x1dc
> driver_register+0xbc/0xf8
> __platform_driver_register+0x24/0x30
> ufs_renesas_platform_init+0x1c/0x28
> do_one_initcall+0x84/0x1f4
> kernel_init_freeable+0x238/0x23c
> kernel_init+0x20/0x120
> ret_from_fork+0x10/0x20
Note that after "[PATCH v3 1/2] scsi: ufs: core: Ensure clk_gating.lock
is used only after initialization", I no longer see the above BUG(), so
I don't think it's a good idea to include this log.
> The root cause of the issue is that `clk_gating.state` is being toggled
> even if clock gating is not allowed. This can lead to the spinlock being
> used before it is properly initialized.
Which doesn't mean the underlying issue no longer exists...
> The fix is to add a check for `hba->clk_gating.is_initialized` before
> toggling `clk_gating.state` in `ufshcd_setup_clocks`. Since
> `clk_gating.lock` is now initialized unconditionally, this is for
> documentation purposes, to ensure clarity in the code. The primary fix
> remains to prevent toggling the `clk_gating.state` if clock gating is
> not allowed.
>
> Fixes: 1ab27c9cf8b6 ("ufs: Add support for clock gating")
> Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> Signed-off-by: Avri Altman <avri.altman@xxxxxxx>
Seems to work fine on R-Car S4 SK, so
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
