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debugfs: regset32: Add Runtime PM support

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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 lock-ups.

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@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Geert Uytterhoeven 2020-02-11 19:18:55 +01:00 committed by Herbert Xu
parent 9e00df7156
commit 30332eeefe
2 changed files with 9 additions and 0 deletions
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8
fs/debugfs/file.c
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@ -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>
@ -1060,7 +1061,14 @@ 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;
}

1
include/linux/debugfs.h
View file

@ -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;