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@xxxxxxxxx>
Reviewed-by: Niklas Söderlund <niklas.soderlund@xxxxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
Affected drivers:
- drivers/crypto/ccree (fixed)
- drivers/gpu/drm/msm/disp/dpu1
- drivers/usb/dwc3
- drivers/usb/host/ehci-omap.c
- drivers/usb/host/ehci-tegra.c
- drivers/usb/host/ohci-platform.c
- drivers/usb/host/xhci-dbgcap.c
- drivers/usb/host/xhci-histb.c
- drivers/usb/host/xhci-hub.c
- drivers/usb/host/xhci-mtk.c
- drivers/usb/host/xhci-pci.c
- drivers/usb/host/xhci-tegra.c
- drivers/usb/host/xhci.c
- drivers/usb/mtu3
- drivers/usb/musb
drivers/usb/host/xhci-plat.c
Some drivers call pm_runtime_forbid(), but given the comment "users
should enable runtime pm using power/control in sysfs", this can be
overridden from userspace?
v2:
- Add Reviewed-by, Acked-by,
- s/locks/lock-ups/.
---
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 634b09d18b77f46f..204734f8d1c6d648 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>
@@ -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 3d013de64f70ec42..ad416853e722fca7 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;
--
2.17.1
