On Fri, Jan 24, 2020 at 02:29:56PM +0100, Geert Uytterhoeven wrote:
> Hardware registers of devices under control of power management cannot
> be accessed at all times. If such a device is suspended, register
> accesses may lead to undefined behavior, like reading bogus values, or
> causing exceptions or system locks.
>
> Extend struct debugfs_regset32 with an optional field to let device
> drivers specify the device the registers in the set belong to. This
> allows debugfs_show_regset32() to make sure the device is resumed while
> its registers are being read.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> ---
> fs/debugfs/file.c | 8 ++++++++
> include/linux/debugfs.h | 1 +
> 2 files changed, 9 insertions(+)
>
> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> index dede25247b81f72a..5e52d68421c678f2 100644
> --- a/fs/debugfs/file.c
> +++ b/fs/debugfs/file.c
> @@ -18,6 +18,7 @@
> #include <linux/slab.h>
> #include <linux/atomic.h>
> #include <linux/device.h>
> +#include <linux/pm_runtime.h>
> #include <linux/poll.h>
> #include <linux/security.h>
>
> @@ -1057,7 +1058,14 @@ static int debugfs_show_regset32(struct seq_file *s, void *data)
> {
> struct debugfs_regset32 *regset = s->private;
>
> + if (regset->dev)
> + pm_runtime_get_sync(regset->dev);
> +
> debugfs_print_regs32(s, regset->regs, regset->nregs, regset->base, "");
> +
> + if (regset->dev)
> + pm_runtime_put(regset->dev);
> +
> return 0;
> }
>
> diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
> index bf9b6cafa4c26a68..5d0783ae09f365ac 100644
> --- a/include/linux/debugfs.h
> +++ b/include/linux/debugfs.h
> @@ -35,6 +35,7 @@ struct debugfs_regset32 {
> const struct debugfs_reg32 *regs;
> int nregs;
> void __iomem *base;
> + struct device *dev; /* Optional device for Runtime PM */
> };
>
> extern struct dentry *arch_debugfs_dir;
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
