linux-kernel - Re: [PATCH v8 4/9] usb: dwc3: core: Skip setting event buffers for host only controllers

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Message-ID: <ZGN0W0YbIjzmQnH1@hovoldconsulting.com>
Date:   Tue, 16 May 2023 14:17:31 +0200
From:   Johan Hovold <johan@...nel.org>
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>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, quic_pkondeti@...cinc.com,
        quic_ppratap@...cinc.com, quic_wcheng@...cinc.com,
        quic_jackp@...cinc.com, quic_harshq@...cinc.com,
        ahalaney@...hat.com
Subject: Re: [PATCH v8 4/9] usb: dwc3: core: Skip setting event buffers for
 host only controllers

On Sun, May 14, 2023 at 11:19:12AM +0530, 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 setup them up during core_init 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.
> 
> Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
> ---
>  drivers/usb/dwc3/core.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index e983aef1fb93..46192d08d1b6 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -505,6 +505,11 @@ static int dwc3_alloc_event_buffers(struct dwc3 *dwc, unsigned int length)
>  int dwc3_event_buffers_setup(struct dwc3 *dwc)
>  {
>  	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;
>  
>  	evt = dwc->ev_buf;

How about adding this check to dwc3_alloc_event_buffers() instead as
there should be no need to allocate buffer that you never use?

Then you can just check dwc->ev_buf here and elsewhere.

Johan