linux-kernel - Re: [PATCH v2 3/7] usb: dwc3: Calculate REFCLKPER based on reference clock

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Date:   Thu, 20 Jan 2022 16:53:44 +0000
From:   Robert Hancock <robert.hancock@...ian.com>
To:     "sean.anderson@...o.com" <sean.anderson@...o.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
CC:     "bjagadee@...eaurora.org" <bjagadee@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Thinh.Nguyen@...opsys.com" <Thinh.Nguyen@...opsys.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "baruch@...s.co.il" <baruch@...s.co.il>
Subject: Re: [PATCH v2 3/7] usb: dwc3: Calculate REFCLKPER based on reference
 clock

On Tue, 2022-01-18 at 19:24 -0500, Sean Anderson wrote:
> Instead of using a special property to determine the reference clock
> period, use the rate of the reference clock. When we have a legacy
> snps,ref-clock-period-ns property and no reference clock, use it
> instead. Fractional clocks are not currently supported, and will be
> dealt with in the next commit.
> 
> Signed-off-by: Sean Anderson <sean.anderson@...o.com>
> ---
> 
> (no changes since v1)
> 
>  drivers/usb/dwc3/core.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 699ab9abdc47..5214daceda86 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -348,13 +348,22 @@ static void dwc3_frame_length_adjustment(struct dwc3
> *dwc)
>  static void dwc3_ref_clk_period(struct dwc3 *dwc)
>  {
>  	u32 reg;
> +	unsigned long rate, period;
>  
> -	if (dwc->ref_clk_per == 0)
> +	if (dwc->ref_clk) {
> +		rate = clk_get_rate(dwc->ref_clk);
> +		if (!rate)
> +			return;
> +		period = NSEC_PER_SEC / rate;
> +	} else if (dwc->ref_clk_per) {
> +		period = dwc->ref_clk_per;
> +	} else {
>  		return;
> +	}
>  
>  	reg = dwc3_readl(dwc->regs, DWC3_GUCTL);
>  	reg &= ~DWC3_GUCTL_REFCLKPER_MASK;
> -	reg |=  FIELD_PREP(DWC3_GUCTL_REFCLKPER_MASK, dwc->ref_clk_per);
> +	reg |=  FIELD_PREP(DWC3_GUCTL_REFCLKPER_MASK, period);
>  	dwc3_writel(dwc->regs, DWC3_GUCTL, reg);
>  }
>  

Looks good here on a ZynqMP board.

Reviewed-by: Robert Hancock <robert.hancock@...ian.com>
Tested-by: Robert Hancock <robert.hancock@...ian.com>