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

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Message-ID: <52b5c1ac-ac69-2ca7-1bf4-01b1f53b1634@quicinc.com>
Date:   Tue, 16 May 2023 19:58:10 +0530
From:   Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
To:     Johan Hovold <johan@...nel.org>
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 5/16/2023 5:47 PM, Johan Hovold wrote:
> 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.
> 

Thanks for this idea. We can save 4096 bytes from being allocated this 
way. Will get this in next version.

Regards,
Krishna,