[RFC 3/3] Re: [PATCH] mpc52xx_psc_spi: fix it for CONFIG_PPC_MERGE

[David Brownell]

On Friday 25 May 2007, Domen Puncer wrote:

> For clk.h, it does seem quite some code, compared what's there currently.

You're using it wrong then ...


> --- work-powerpc.git.orig/drivers/spi/mpc52xx_psc_spi.c
> +++ work-powerpc.git/drivers/spi/mpc52xx_psc_spi.c
> @@ -18,6 +18,7 @@
>  
>  #if defined(CONFIG_PPC_MERGE)
>  #include <asm/of_platform.h>
> +#include <linux/clk.h>
>  #else
>  #include <linux/platform_device.h>
>  #endif
> @@ -106,13 +107,52 @@ static void mpc52xx_psc_spi_activate_cs(
>  	/* Set clock frequency and bits per word
>  	 * Because psc->ccr is defined as 16bit register instead of 32bit
>  	 * just set the lower byte of BitClkDiv
> +	 * Because BitClkDiv is 8-bit on mpc5200. Lets stay compatible.
>  	 */
> +#if defined(CONFIG_PPC_MERGE)
>  	ccr = in_be16(&psc->ccr);
>  	ccr &= 0xFF00;
> +	{
> +		u8 bitclkdiv = 2;	/* minimum bitclkdiv */
> +		int speed = cs->speed_hz ? cs->speed_hz : 1000000;
> +		char clk_name[10];
> +		struct clk *clk;	// TODO into mps, clk_get, clk_put
> +		int mclk;
> +		int system;
> +		/*
> +		 * pscclk = mclk/(bitclkdiv+1))		bitclkdiv is 8-bit, >= 2
> +		 * mclk = fsys/(mclkdiv+1)		mclkdiv is 9-bit, >= 1
> +		 * as mclkdiv has higher precision, we want is as big as possible
> +		 * => we get < 0.002*clock error
> +		 */
> +
> +		snprintf(clk_name, 10, "psc%i_mclk", spi->master->bus_num);
> +
> +		clk = clk_get(&spi->dev, clk_name);

Don't expect spi->dev to have a clock.  Instead, the host controller
has a clock, which would be looked up the probe() routine, then released
in remove():  clock = clk_get(dev, "clockname"), with the clock framework
using "dev" to identify which clock it returns.  (That is, the function
clock for all SPI controllers would have the same name ... not for
example "spi1_fclk", "spi2_fclk", etc. but instead "spi_fclk".)


> +		if (!clk)
> +			dev_err(&spi->dev, "couldn't get %s clock\n", clk_name);
> +
> +		system = clk_get_rate(clk_get_parent(clk));	// TODO, checking, refcounting
> +		mclk = speed * (bitclkdiv+1);
> +		if (system/mclk > 512) { /* bigger than mclkdiv */
> +			bitclkdiv = system/512/speed;
> +			mclk = speed * (bitclkdiv+1);
> +		}
> +
> +		if (clk_set_rate(clk, mclk))
> +			dev_err(&spi->dev, "couldn't set %s's rate\n", clk_name);
> +
> +		dev_info(&spi->dev, "clock: wanted: %i, got: %li\n", speed,
> +				clk_round_rate(clk, mclk) / (bitclkdiv+1));
> +
> +		ccr |= bitclkdiv;
> +	}
> +#else
>  	if (cs->speed_hz)
>  		ccr |= (MCLK / cs->speed_hz - 1) & 0xFF;
>  	else /* by default SPI Clk 1MHz */
>  		ccr |= (MCLK / 1000000 - 1) & 0xFF;
> +#endif
>  	out_be16(&psc->ccr, ccr);
>  	mps->bits_per_word = cs->bits_per_word;
>  
\