[EXTERNAL] Re: [PATCH] usb: cdns3: gadget.c: Set fast access bit

[Ravi Gunasekaran]

Hi Roger,

On 05/05/23 6:02 pm, Roger Quadros wrote:
> Hi Ravi,
> 
> On 05/05/2023 15:13, Ravi Gunasekaran wrote:
>> From: Aswath Govindraju <a-govindraju at ti.com>
>>
>> When the device port is in a low power state [U3/L2/Not Connected],
>> accesses to usb device registers may take a long time. This could lead to
>> potential core hang when the controller registers are accessed after the
>> port is disabled by setting DEVDS field. Setting the fast register access
>> bit ensures that the PHY clock is keeping up in active state.
>>
>> Therefore, set fast access bit to ensure the accesses to device registers
>> are quick even in low power states.
>>
>> Signed-off-by: Aswath Govindraju <a-govindraju at ti.com>
>> ---
>>  drivers/usb/cdns3/gadget.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
>> index fcaeab9cc1..fddc8c931a 100644
>> --- a/drivers/usb/cdns3/gadget.c
>> +++ b/drivers/usb/cdns3/gadget.c
>> @@ -2321,6 +2321,9 @@ static void cdns3_gadget_config(struct cdns3_device *priv_dev)
>>  	writel(USB_IEN_INIT, &regs->usb_ien);
>>  	writel(USB_CONF_CLK2OFFDS | USB_CONF_L1DS, &regs->usb_conf);
>>  
>> +	/* Set the Fast access bit */
>> +	writel(PUSB_PWR_FST_REG_ACCESS, &priv_dev->regs->usb_pwr);
>> +
> 
> Should this be done in cdns3_gadget_udc_start() so it is symmetric?
> 

cdns3_gadget_config() is called in cdns3_gadget_udc_start() and 
cdns3_gadget_resume(). These settings seems to be needed during resume
as well.

>>  	cdns3_configure_dmult(priv_dev, NULL);
>>  
>>  	cdns3_gadget_pullup(&priv_dev->gadget, 1);
>> @@ -2378,6 +2381,7 @@ static int cdns3_gadget_udc_stop(struct usb_gadget *gadget)
>>  
>>  	/* disable interrupt for device */
>>  	writel(0, &priv_dev->regs->usb_ien);
>> +	writel(0, &priv_dev->regs->usb_pwr);
>>  	writel(USB_CONF_DEVDS, &priv_dev->regs->usb_conf);
>>  
>>  	return ret;
>>
>> base-commit: a25dcda452bf6a6de72764a8d990d72e5def643d
> 
> cheers,
> -roger

-- 
Regards,
Ravi