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

[Roger Quadros <rogerq@kernel.org>]

Hi Ravi,

On 05/05/2023 15:13, Ravi Gunasekaran wrote:
> From: Aswath Govindraju <a-govindraju@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@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_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