Re: [PATCH 1/2] debugfs: regset32: Add Runtime PM support

[Greg Kroah-Hartman]

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>