debugfs: regset32: Add Runtime PM support

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>

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 634b09d18b77f46f5a24f0cd0f75ab8fae0e7876..204734f8d1c6d6485524d66c8e1281e6eff98fef 100644 (file)
--- 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>
 
@@ -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;
 }
 

diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 3d013de64f70ec42e330ba04546b34fca02bd2b1..ad416853e722fca742944d13c1085255093229c8 100644 (file)
--- 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;