linux-kernel - Re: [PATCH v2 5/7] usb: dwc3: Add snps,ref-clock-frequency-hz property for ACPI

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Message-ID: <5275ea80-400e-d1de-f03e-c2ea81f959dc@synopsys.com>
Date:   Mon, 24 Jan 2022 22:44:14 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Sean Anderson <sean.anderson@...o.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
CC:     Felipe Balbi <balbi@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Balaji Prakash J <bjagadee@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Robert Hancock <robert.hancock@...ian.com>,
        Baruch Siach <baruch@...s.co.il>
Subject: Re: [PATCH v2 5/7] usb: dwc3: Add snps,ref-clock-frequency-hz
 property for ACPI

Sean Anderson wrote:
> This property allows setting the reference clock frequency properly for
> ACPI-based systems. It is not documented under dt-bindings, since it is
> not intended for use on DT-based systems. DT-based systems should use
> the clocks property instead.
> 
> Frequency is preferred over period since it has greater precision when
> used in calculations.
> 
> Signed-off-by: Sean Anderson <sean.anderson@...o.com>
> ---
> 
> Changes in v2:
> - New
> 
>  drivers/usb/dwc3/core.c | 6 ++++--
>  drivers/usb/dwc3/core.h | 4 +++-
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 883e119377f0..5f3dc5f6cbcb 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -350,8 +350,8 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc)
>  	u32 reg;
>  	unsigned long decr, fladj, rate, period;
>  
> -	if (dwc->ref_clk) {
> -		rate = clk_get_rate(dwc->ref_clk);
> +	if (dwc->ref_clk || dwc->ref_clk_freq) {
> +		rate = clk_get_rate(dwc->ref_clk) ?: dwc->ref_clk_freq;
>  		if (!rate)
>  			return;
>  		period = NSEC_PER_SEC / rate;
> @@ -1492,6 +1492,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  				 &dwc->fladj);
>  	device_property_read_u32(dev, "snps,ref-clock-period-ns",
>  				 &dwc->ref_clk_per);
> +	device_property_read_u32(dev, "snps,ref-clock-frequency-hz",
> +				 &dwc->ref_clk_freq);

Please also document in dwc3 DT file whenever we add a new property.

Thanks,
Thinh

>  
>  	dwc->dis_metastability_quirk = device_property_read_bool(dev,
>  				"snps,dis_metastability_quirk");
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index eb9c1efced05..00a792459fec 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -988,7 +988,8 @@ struct dwc3_scratchpad_array {
>   * @regs: base address for our registers
>   * @regs_size: address space size
>   * @fladj: frame length adjustment
> - * @ref_clk_per: reference clock period configuration
> + * @ref_clk_per: reference clock period; deprecated in favor of @ref_clk_freq
> + * @ref_clk_freq: reference clock frequency to use if @ref_clk is missing
>   * @irq_gadget: peripheral controller's IRQ number
>   * @otg_irq: IRQ number for OTG IRQs
>   * @current_otg_role: current role of operation while using the OTG block
> @@ -1171,6 +1172,7 @@ struct dwc3 {
>  
>  	u32			fladj;
>  	u32			ref_clk_per;
> +	u32			ref_clk_freq;
>  	u32			irq_gadget;
>  	u32			otg_irq;
>  	u32			current_otg_role;