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

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Message-ID: <20230623222754.auuce7y6c2e7ymvw@synopsys.com>
Date:   Fri, 23 Jun 2023 22:27:57 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Krishna Kurapati <quic_kriskura@...cinc.com>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Felipe Balbi <balbi@...nel.org>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        Johan Hovold <johan@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "quic_pkondeti@...cinc.com" <quic_pkondeti@...cinc.com>,
        "quic_ppratap@...cinc.com" <quic_ppratap@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        "quic_harshq@...cinc.com" <quic_harshq@...cinc.com>,
        "ahalaney@...hat.com" <ahalaney@...hat.com>,
        "quic_shazhuss@...cinc.com" <quic_shazhuss@...cinc.com>
Subject: Re: [PATCH v9 04/10] usb: dwc3: core: Skip setting event buffers for
 host only controllers

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@...nel.org>
> Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.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
>