Re: [PATCH v9 04/10] usb: dwc3: core: Skip setting event buffers for host only controllers

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

On Wed, Jun 21, 2023, Krishna Kurapati wrote:
> On some SoC's like SA8295P where the tertiary controller is host-only
> capable, GEVTADDRHI/LO, GEVTSIZ, GEVTCOUNT registers are not accessible.
> Trying to access them leads to a crash.
> 
> For DRD/Peripheral supported controllers, event buffer setup is done
> again in gadget_pullup. Skip setup or cleanup of event buffers if
> controller is host-only capable.
> 
> Suggested-by: Johan Hovold <johan@kernel.org>
> Signed-off-by: Krishna Kurapati <quic_kriskura@quicinc.com>
> ---
>  drivers/usb/dwc3/core.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 32ec05fc242b..e1ebae54454f 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -486,6 +486,11 @@ static void dwc3_free_event_buffers(struct dwc3 *dwc)
>  static int dwc3_alloc_event_buffers(struct dwc3 *dwc, unsigned int length)
>  {
>  	struct dwc3_event_buffer *evt;
> +	unsigned int hw_mode;
> +
> +	hw_mode = DWC3_GHWPARAMS0_MODE(dwc->hwparams.hwparams0);
> +	if (hw_mode == DWC3_GHWPARAMS0_MODE_HOST)
> +		return 0;

This is a little awkward. Returning 0 here indicates that this function
was successful, and the event buffers were allocated based on the
function name. Do this check outside of dwc3_alloc_one_event_buffer()
and specifically set dwc->ev_buf = NULL if that's the case.

Thanks,
Thinh

>  
>  	evt = dwc3_alloc_one_event_buffer(dwc, length);
>  	if (IS_ERR(evt)) {
> @@ -507,6 +512,9 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
>  {
>  	struct dwc3_event_buffer	*evt;
>  
> +	if (!dwc->ev_buf)
> +		return 0;
> +
>  	evt = dwc->ev_buf;
>  	evt->lpos = 0;
>  	dwc3_writel(dwc->regs, DWC3_GEVNTADRLO(0),
> @@ -524,6 +532,9 @@ void dwc3_event_buffers_cleanup(struct dwc3 *dwc)
>  {
>  	struct dwc3_event_buffer	*evt;
>  
> +	if (!dwc->ev_buf)
> +		return;
> +
>  	evt = dwc->ev_buf;
>  
>  	evt->lpos = 0;
> -- 
> 2.40.0
>