Subject: Re: [PATCH v3 27/31] net: can: mscan: add common clock support for mpc512x

From: Marc Kleine-Budde <[email-masked]>
Date: Mon, 22 Jul 2013 15:04:52 +0200

On 07/22/2013 02:14 PM, Gerhard Sittig wrote:
> implement a .get_clock() callback for the MPC512x platform which uses
> the common clock infrastructure (eliminating direct access to the clock
> control registers from within the CAN network driver), and provide the
> corresponding .put_clock() callback to release resources after use
> 
> keep the previous implementation of MPC512x support in place during
> migration, since common clock support is optional
> 
> this change is neutral to the MPC5200 platform
> 
> Signed-off-by: Gerhard Sittig <[email-masked]>
> ---
>  drivers/net/can/mscan/mpc5xxx_can.c |  169 +++++++++++++++++++++++++++++++++++
>  1 file changed, 169 insertions(+)
> 
> diff --git a/drivers/net/can/mscan/mpc5xxx_can.c b/drivers/net/can/mscan/mpc5xxx_can.c
> index e59b3a3..4897929 100644
> --- a/drivers/net/can/mscan/mpc5xxx_can.c
> +++ b/drivers/net/can/mscan/mpc5xxx_can.c
> @@ -109,6 +109,167 @@ static u32 mpc52xx_can_get_clock(struct platform_device *ofdev,
>  #endif /* CONFIG_PPC_MPC52xx */
>  
>  #ifdef CONFIG_PPC_MPC512x
> +
> +#if IS_ENABLED(CONFIG_COMMON_CLK)
> +
> +static u32 mpc512x_can_get_clock(struct platform_device *ofdev,
> +				 const char *clock_source, int *mscan_clksrc)
> +{
> +	struct device_node *np;
> +	u32 clockdiv;
> +	enum {
> +		CLK_FROM_AUTO,
> +		CLK_FROM_IPS,
> +		CLK_FROM_SYS,
> +		CLK_FROM_REF,
> +	} clk_from;
> +	struct clk *clk_in, *clk_can;
> +	unsigned long freq_calc;
> +	struct mscan_priv *priv;
> +
> +	/* the caller passed in the clock source spec that was read from
> +	 * the device tree, get the optional clock divider as well
> +	 */
> +	np = ofdev->dev.of_node;
> +	clockdiv = 1;
> +	of_property_read_u32(np, "fsl,mscan-clock-divider", &clockdiv);
> +	dev_dbg(&ofdev->dev, "device tree specs: clk src[%s] div[%d]\n",
> +		clock_source ? clock_source : "<NULL>", clockdiv);
> +
> +	/* when clock-source is 'ip', the CANCTL1[CLKSRC] bit needs to
> +	 * get set, and the 'ips' clock is the input to the MSCAN
> +	 * component
> +	 *
> +	 * for clock-source values of 'ref' or 'sys' the CANCTL1[CLKSRC]
> +	 * bit needs to get cleared, an optional clock-divider may have
> +	 * been specified (the default value is 1), the appropriate
> +	 * MSCAN related MCLK is the input to the MSCAN component
> +	 *
> +	 * in the absence of a clock-source spec, first an optimal clock
> +	 * gets determined based on the 'sys' clock, if that fails the
> +	 * 'ref' clock is used
> +	 */
> +	clk_from = CLK_FROM_AUTO;
> +	if (clock_source) {
> +		/* interpret the device tree's spec for the clock source */
> +		if (!strcmp(clock_source, "ip"))
> +			clk_from = CLK_FROM_IPS;
> +		else if (!strcmp(clock_source, "sys"))
> +			clk_from = CLK_FROM_SYS;
> +		else if (!strcmp(clock_source, "ref"))
> +			clk_from = CLK_FROM_REF;
> +		else
> +			goto err_invalid;
> +		dev_dbg(&ofdev->dev, "got a clk source spec[%d]\n", clk_from);
> +	}
> +	if (clk_from == CLK_FROM_AUTO) {
> +		/* no spec so far, try the 'sys' clock; round to the
> +		 * next MHz and see if we can get a multiple of 16MHz
> +		 */
> +		dev_dbg(&ofdev->dev, "no clk source spec, trying SYS\n");
> +		clk_in = devm_clk_get(&ofdev->dev, "sys");
> +		if (IS_ERR(clk_in))
> +			goto err_notavail;
> +		freq_calc = clk_get_rate(clk_in);
> +		freq_calc +=  499999;
> +		freq_calc /= 1000000;
> +		freq_calc *= 1000000;
> +		if ((freq_calc % 16000000) == 0) {
> +			clk_from = CLK_FROM_SYS;
> +			clockdiv = freq_calc / 16000000;
> +			dev_dbg(&ofdev->dev,
> +				"clk fit, sys[%lu] div[%d] freq[%lu]\n",
> +				freq_calc, clockdiv, freq_calc / clockdiv);
> +		}
> +	}
> +	if (clk_from == CLK_FROM_AUTO) {
> +		/* no spec so far, use the 'ref' clock */
> +		dev_dbg(&ofdev->dev, "no clk source spec, trying REF\n");
> +		clk_in = devm_clk_get(&ofdev->dev, "ref");
> +		if (IS_ERR(clk_in))
> +			goto err_notavail;
> +		clk_from = CLK_FROM_REF;
> +		freq_calc = clk_get_rate(clk_in);
> +		dev_dbg(&ofdev->dev,
> +			"clk fit, ref[%lu] (no div) freq[%lu]\n",
> +			freq_calc, freq_calc);
> +	}
> +
> +	/* select IPS or MCLK as the MSCAN input (returned to the caller),
> +	 * setup the MCLK mux source and rate if applicable, apply the
> +	 * optionally specified or derived above divider, and determine
> +	 * the actual resulting clock rate to return to the caller
> +	 */
> +	switch (clk_from) {
> +	case CLK_FROM_IPS:
> +		clk_can = devm_clk_get(&ofdev->dev, "ips");
> +		if (IS_ERR(clk_can))
> +			goto err_notavail;
> +		if (clk_prepare(clk_can)) {

I would just call prepare_enable in the main mscan driver, then we don't
need a special "clock is prepared but not enabled" contract.

> +			devm_clk_put(&ofdev->dev, clk_can);

not needed, as this driver instance will fail, doesn't it?

> +			goto err_notavail;
> +		}
> +		priv = netdev_priv(dev_get_drvdata(&ofdev->dev));
> +		priv->clk_can = clk_can;
> +		freq_calc = clk_get_rate(clk_can);
> +		*mscan_clksrc = MSCAN_CLKSRC_IPS;
> +		dev_dbg(&ofdev->dev, "clk from IPS, clksrc[%d] freq[%lu]\n",
> +			*mscan_clksrc, freq_calc);
> +		break;
> +	case CLK_FROM_SYS:
> +	case CLK_FROM_REF:
> +		clk_can = devm_clk_get(&ofdev->dev, "mclk");
> +		if (IS_ERR(clk_can))
> +			goto err_notavail;
> +		if (clk_prepare(clk_can)) {
> +			devm_clk_put(&ofdev->dev, clk_can);

same here

> +			goto err_notavail;
> +		}
> +		priv = netdev_priv(dev_get_drvdata(&ofdev->dev));
> +		priv->clk_can = clk_can;
> +		if (clk_from == CLK_FROM_SYS)
> +			clk_in = devm_clk_get(&ofdev->dev, "sys");
> +		if (clk_from == CLK_FROM_REF)
> +			clk_in = devm_clk_get(&ofdev->dev, "ref");
> +		if (IS_ERR(clk_in))
> +			goto err_notavail;
> +		clk_set_parent(clk_can, clk_in);
> +		freq_calc = clk_get_rate(clk_in);
> +		freq_calc /= clockdiv;
> +		clk_set_rate(clk_can, freq_calc);
> +		freq_calc = clk_get_rate(clk_can);
> +		*mscan_clksrc = MSCAN_CLKSRC_BUS;
> +		dev_dbg(&ofdev->dev, "clk from MCLK, clksrc[%d] freq[%lu]\n",
> +			*mscan_clksrc, freq_calc);
> +		break;
> +	default:
> +		goto err_invalid;
> +	}
> +
> +	return freq_calc;
> +
> +err_invalid:
> +	dev_err(&ofdev->dev, "invalid clock source specification\n");
> +	return 0;

return 0 in case of error? Please add a comment what this 0 means here.
> +
> +err_notavail:
> +	dev_err(&ofdev->dev, "cannot acquire or setup clock source\n");
> +	return 0;
> +}
> +
> +static void mpc512x_can_put_clock(struct platform_device *ofdev)
> +{
> +	struct mscan_priv *priv;
> +
> +	priv = netdev_priv(dev_get_drvdata(&ofdev->dev));
> +	if (priv->clk_can) {
> +		clk_unprepare(priv->clk_can);
> +		devm_clk_put(&ofdev->dev, priv->clk_can);

devm_clk_put can be removed, it's called automatically.

> +	}
> +}
> +
> +#else	/* COMMON_CLK */
> +
>  struct mpc512x_clockctl {
>  	u32 spmr;		/* System PLL Mode Reg */
>  	u32 sccr[2];		/* System Clk Ctrl Reg 1 & 2 */
> @@ -239,12 +400,18 @@ exit_put:
>  	of_node_put(np_clock);
>  	return freq;
>  }
> +
> +#define mpc512x_can_put_clock NULL
> +
> +#endif	/* COMMON_CLK */
> +
>  #else /* !CONFIG_PPC_MPC512x */
>  static u32 mpc512x_can_get_clock(struct platform_device *ofdev,
>  				 const char *clock_name, int *mscan_clksrc)
>  {
>  	return 0;
>  }
> +#define mpc512x_can_put_clock NULL
>  #endif /* CONFIG_PPC_MPC512x */
>  
>  static const struct of_device_id mpc5xxx_can_table[];
> @@ -386,11 +553,13 @@ static int mpc5xxx_can_resume(struct platform_device *ofdev)
>  static const struct mpc5xxx_can_data mpc5200_can_data = {
>  	.type = MSCAN_TYPE_MPC5200,
>  	.get_clock = mpc52xx_can_get_clock,
> +	/* .put_clock not applicable */
>  };
>  
>  static const struct mpc5xxx_can_data mpc5121_can_data = {
>  	.type = MSCAN_TYPE_MPC5121,
>  	.get_clock = mpc512x_can_get_clock,
> +	.put_clock = mpc512x_can_put_clock,
>  };
>  
>  static const struct of_device_id mpc5xxx_can_table[] = {
> 

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |