Re: [PATCH v10] usb: dwc3: debugfs: Resume dwc3 before accessing registers

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Tue, May 09, 2023, Johan Hovold wrote:
> On Tue, May 09, 2023 at 08:18:36PM +0530, Udipto Goswami wrote:
> > When the dwc3 device is runtime suspended, various required clocks are in
> > disabled state 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, make sure to resume
> > dwc3 then allow the function to proceed.
> > 
> > Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
> > Cc: stable@vger.kernel.org #3.2: 30332eeefec8: debugfs: regset32: Add Runtime PM support
> > Signed-off-by: Udipto Goswami <quic_ugoswami@quicinc.com>
> > ---
> > v10: Re-wrote the subject & the commit text along with the dependency.
> > v9: Fixed function dwc3_rx_fifo_size_show & return values in function
> > 	dwc3_link_state_write along with minor changes for code symmetry.
> > v8: Replace pm_runtime_get_sync with pm_runtime_resume_and get.
> > v7: Replaced pm_runtime_put with pm_runtime_put_sync & returned proper values.
> > v6: Added changes to handle get_dync failure appropriately.
> > v5: Reworked the patch to resume dwc3 while accessing the registers.
> > v4: Introduced pm_runtime_get_if_in_use in order to make sure dwc3 isn't
> > 	suspended while accessing the registers.
> > v3: Replace pr_err to dev_err. 
> > v2: Replaced return 0 with -EINVAL & seq_puts with pr_err.
> 
> I've verified that this prevents the system from hanging when accessing
> the debugfs interface while the controller is runtime suspended on the
> ThinkPad X13s (sc8280xp):
> 
> Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
> Tested-by: Johan Hovold <johan+linaro@kernel.org>
> 
> Johan

Thanks for the review and test!

Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

Thanks,
Thinh