On Tue, Apr 04, 2023 at 03:30:55PM +0530, Udipto Goswami wrote:
> When the dwc3 device is runtime suspended, various required clocks would
> get disabled and it is not guaranteed that access to any registers would
> work. Depending on the SoC glue, a register read could be as benign as
> returning 0 or be fatal enough to hang the system.
>
> In order to prevent such scenarios of fatal errors, bail out of debugfs
> function is dwc3 is suspended.
>
> Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
> Signed-off-by: Udipto Goswami <quic_ugoswami@xxxxxxxxxxx>
> ---
> v4: Introduced pm_runtime_get_if_in_use in order to make sure dwc3 isn't
> suspended while accessing the registers.
>
> drivers/usb/dwc3/debugfs.c | 191 ++++++++++++++++++++++++++++++++-----
> 1 file changed, 169 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
> index 850df0e6bcab..e57cafb7da4b 100644
> --- a/drivers/usb/dwc3/debugfs.c
> +++ b/drivers/usb/dwc3/debugfs.c
> @@ -543,13 +543,25 @@ static int dwc3_link_state_show(struct seq_file *s, void *unused)
> enum dwc3_link_state state;
> u32 reg;
> u8 speed;
> + int ret = 0;
> +
> + ret = pm_runtime_get_if_in_use(dwc->dev);
> + /* check if pm runtime get fails, bail out early */
> + if (ret < 0)
> + goto err_nolock;
> +
> + if (!ret) {
> + ret = -EINVAL;
> + dev_err(dwc->dev,
> + "Invalid operation, DWC3 suspended!");
> + goto err_nolock;
> + }
This is backwards. If you need the device to be active to access these
registers then you should resume it unconditionally instead of failing.
Johan
