linux-kernel - Re: [PATCH 2/2] clk: X1000: Add support for calculat REFCLK of USB PHY.

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Date:   Fri, 26 Jun 2020 19:36:10 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     周琰杰 <zhouyanjie@...yeetech.com>
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        sboyd@...nel.org, mturquette@...libre.com,
        dongsheng.qiu@...enic.com, aric.pzqi@...enic.com,
        rick.tyliu@...enic.com, yanfei.li@...enic.com,
        sernia.zhou@...mail.com, zhenwenjin@...il.com
Subject: Re: [PATCH 2/2] clk: X1000: Add support for calculat REFCLK of USB
 PHY.

Hi Zhou,

Le sam. 27 juin 2020 à 0:48, 周琰杰 (Zhou Yanjie) 
<zhouyanjie@...yeetech.com> a écrit :
> Add new functions to "x1000_otg_phy_ops" to calculat the rate of 
> REFCLK,
> which is needed by USB PHY in the Ingenic X1000 SoC.
> 
> Tested-by: 周正 (Zhou Zheng) <sernia.zhou@...mail.com>
> Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@...yeetech.com>
> ---
>  drivers/clk/ingenic/x1000-cgu.c | 113 
> ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 113 insertions(+)
> 
> diff --git a/drivers/clk/ingenic/x1000-cgu.c 
> b/drivers/clk/ingenic/x1000-cgu.c
> index 453f3323cb99..a61c16f98a11 100644
> --- a/drivers/clk/ingenic/x1000-cgu.c
> +++ b/drivers/clk/ingenic/x1000-cgu.c
> @@ -48,8 +48,114 @@
>  #define USBPCR_SIDDQ		BIT(21)
>  #define USBPCR_OTG_DISABLE	BIT(20)
> 
> +/* bits within the USBPCR1 register */
> +#define USBPCR1_REFCLKSEL_SHIFT	26
> +#define USBPCR1_REFCLKSEL_MASK	(0x3 << USBPCR1_REFCLKSEL_SHIFT)
> +#define USBPCR1_REFCLKSEL_CORE	(0x2 << USBPCR1_REFCLKSEL_SHIFT)
> +#define USBPCR1_REFCLKDIV_SHIFT	24
> +#define USBPCR1_REFCLKDIV_MASK	(0x3 << USBPCR1_REFCLKDIV_SHIFT)
> +#define USBPCR1_REFCLKDIV_48	(0x2 << USBPCR1_REFCLKDIV_SHIFT)
> +#define USBPCR1_REFCLKDIV_24	(0x1 << USBPCR1_REFCLKDIV_SHIFT)
> +#define USBPCR1_REFCLKDIV_12	(0x0 << USBPCR1_REFCLKDIV_SHIFT)
> +
>  static struct ingenic_cgu *cgu;
> 
> +static u8 x1000_otg_phy_get_parent(struct clk_hw *hw)
> +{
> +	/* we only use CLKCORE, revisit if that ever changes */
> +	return 0;
> +}
> +
> +static int x1000_otg_phy_set_parent(struct clk_hw *hw, u8 idx)
> +{
> +	unsigned long flags;
> +	u32 usbpcr1;
> +
> +	if (idx > 0)
> +		return -EINVAL;
> +
> +	spin_lock_irqsave(&cgu->lock, flags);
> +
> +	usbpcr1 = readl(cgu->base + CGU_REG_USBPCR1);
> +	usbpcr1 &= ~USBPCR1_REFCLKSEL_MASK;
> +	/* we only use CLKCORE */
> +	usbpcr1 |= USBPCR1_REFCLKSEL_CORE;
> +	writel(usbpcr1, cgu->base + CGU_REG_USBPCR1);
> +
> +	spin_unlock_irqrestore(&cgu->lock, flags);
> +	return 0;
> +}

If you only support one parent, maybe set that bit in the 
x1000_cgu_init(), then you can drop the get_parent/set_parent.

> +
> +static unsigned long x1000_otg_phy_recalc_rate(struct clk_hw *hw,
> +						unsigned long parent_rate)
> +{
> +	u32 usbpcr1;
> +	unsigned refclk_div;
> +
> +	usbpcr1 = readl(cgu->base + CGU_REG_USBPCR1);
> +	refclk_div = usbpcr1 & USBPCR1_REFCLKDIV_MASK;
> +
> +	switch (refclk_div) {
> +	case USBPCR1_REFCLKDIV_12:
> +		return 12000000;
> +
> +	case USBPCR1_REFCLKDIV_24:
> +		return 24000000;
> +
> +	case USBPCR1_REFCLKDIV_48:
> +		return 48000000;
> +	}

On your setup, what frequency is configured for the "otg" clock? Is it 
48 MHz?

I believe CLKCORE is the OTG core's clock (aka "otg"), and I'm pretty 
sure that these fields only represent CLKCORE/4, CLKCORE/2, CLKCORE/1, 
but the doc expects CLKCORE==48MHz.

In that case the "otg_phy" should be parented to "otg", and the rate 
should be computed according to the parent rate and the divider 
configured.

> +
> +	BUG();

Don't use BUG() - it pisses off Linus :)
And it's reserved for bugs that will take the whole system down, I 
think. Better use WARN().

Cheers,
-Paul

> +	return parent_rate;
> +}
> +
> +static long x1000_otg_phy_round_rate(struct clk_hw *hw, unsigned 
> long req_rate,
> +				      unsigned long *parent_rate)
> +{
> +	if (req_rate < 18000000)
> +		return 12000000;
> +
> +	if (req_rate < 36000000)
> +		return 24000000;
> +
> +	return 48000000;
> +}
> +
> +static int x1000_otg_phy_set_rate(struct clk_hw *hw, unsigned long 
> req_rate,
> +				   unsigned long parent_rate)
> +{
> +	unsigned long flags;
> +	u32 usbpcr1, div_bits;
> +
> +	switch (req_rate) {
> +	case 12000000:
> +		div_bits = USBPCR1_REFCLKDIV_12;
> +		break;
> +
> +	case 24000000:
> +		div_bits = USBPCR1_REFCLKDIV_24;
> +		break;
> +
> +	case 48000000:
> +		div_bits = USBPCR1_REFCLKDIV_48;
> +		break;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	spin_lock_irqsave(&cgu->lock, flags);
> +
> +	usbpcr1 = readl(cgu->base + CGU_REG_USBPCR1);
> +	usbpcr1 &= ~USBPCR1_REFCLKDIV_MASK;
> +	usbpcr1 |= div_bits;
> +	writel(usbpcr1, cgu->base + CGU_REG_USBPCR1);
> +
> +	spin_unlock_irqrestore(&cgu->lock, flags);
> +	return 0;
> +}
> +
>  static int x1000_usb_phy_enable(struct clk_hw *hw)
>  {
>  	void __iomem *reg_opcr		= cgu->base + CGU_REG_OPCR;
> @@ -80,6 +186,13 @@ static int x1000_usb_phy_is_enabled(struct clk_hw 
> *hw)
>  }
> 
>  static const struct clk_ops x1000_otg_phy_ops = {
> +	.get_parent = x1000_otg_phy_get_parent,
> +	.set_parent = x1000_otg_phy_set_parent,
> +
> +	.recalc_rate = x1000_otg_phy_recalc_rate,
> +	.round_rate = x1000_otg_phy_round_rate,
> +	.set_rate = x1000_otg_phy_set_rate,
> +
>  	.enable		= x1000_usb_phy_enable,
>  	.disable	= x1000_usb_phy_disable,
>  	.is_enabled	= x1000_usb_phy_is_enabled,
> --
> 2.11.0
>