Re: [PATCH 1/2 v3] fs_enet/mii-fec.c: fix MII speed calculation

[Grant Likely <grant.likely@secretlab.ca>]

On Wed, Jul 15, 2009 at 9:18 AM, Wolfgang Denk<wd@denx.de> wrote:
> The MII speed calculation was based on the CPU clock (ppc_proc_freq),
> but for MPC512x we must use the bus clock instead.
>
> This patch makes it use the correct clock and makes sure we don't
> clobber reserved bits in the MII_SPEED register.
>
> Signed-off-by: Wolfgang Denk <wd@denx.de>
> Cc: Grant Likely <grant.likely@secretlab.ca>
> Cc: Kumar Gala <galak@kernel.crashing.org>
> Cc: <netdev@vger.kernel.org>
> ---
> Please ignore patch v2, it's crap.
> Hope this is a bit better.
>
>  arch/powerpc/include/asm/mpc5xxx.h   |   10 +++++++++
>  arch/powerpc/sysdev/mpc5xxx_clocks.c |   37 ++++++++++++++++++++++++++++++++++

Drop the common code bit.  The 5200 and 5121 are different devices and
it is a tiny bit of code.  I don't think there is any benefit to
having it as a common function.  Just roll the get_mii_speed function
in the mii-fec driver itself.

Also, this patch can be quite a bit simpler if you use the .data
pointer in the drivers match table to specify the function used to
return the bus clock speed.  Something like this:

static struct of_device_id fs_enet_mdio_fec_match[] = {
	{
		.compatible = "fsl,pq1-fec-mdio",
	},
#if defined(CONFIG_PPC_MPC512x)
	{
		.compatible = "fsl,mpc5121-fec-mdio",
		.data = mpc5xxx_get_bus_frequency,
	},
#endif
	{},
};

and

int *get_bus_freq(of_node *) = data;
if (get_bus_freq)
        bus_freq = get_bus_freq(np);
else
        bus_freq = ppc_proc_freq / 2;

... then do the regular calculation here and add in the additional
robustification you did in this patch.

Heck, you could even eliminate the if/else above if the normal case
you have a get_bus_speed function for the original ppc_proc_freq case,
but I'm not sure if it is worth it.


>  drivers/net/fs_enet/mii-fec.c        |   13 +++++++++--
>  3 files changed, 57 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/mpc5xxx.h b/arch/powerpc/include/asm/mpc5xxx.h
> index 5ce9c5f..86ab29f 100644
> --- a/arch/powerpc/include/asm/mpc5xxx.h
> +++ b/arch/powerpc/include/asm/mpc5xxx.h
> @@ -15,8 +15,18 @@
>
>  #ifndef __ASM_POWERPC_MPC5xxx_H__
>  #define __ASM_POWERPC_MPC5xxx_H__
> +#include <linux/of_platform.h>
>
>  extern unsigned long mpc5xxx_get_bus_frequency(struct device_node *node);
>
> +#if defined(CONFIG_PPC_MPC512x) || defined(CONFIG_PPC_MPC52xx)
> +extern int mpc5xxx_get_mii_speed(struct of_device *ofdev);
> +#else
> +static inline int mpc5xxx_get_mii_speed(struct of_device *ofdev)
> +{
> +       return -1;
> +}
> +#endif
> +
>  #endif /* __ASM_POWERPC_MPC5xxx_H__ */
>
> diff --git a/arch/powerpc/sysdev/mpc5xxx_clocks.c b/arch/powerpc/sysdev/mpc5xxx_clocks.c
> index 34e12f9..e26d12b 100644
> --- a/arch/powerpc/sysdev/mpc5xxx_clocks.c
> +++ b/arch/powerpc/sysdev/mpc5xxx_clocks.c
> @@ -31,3 +31,40 @@ mpc5xxx_get_bus_frequency(struct device_node *node)
>        return p_bus_freq ? *p_bus_freq : 0;
>  }
>  EXPORT_SYMBOL(mpc5xxx_get_bus_frequency);
> +
> +/**
> + *     mpc5xxx_get_mii_speed - Get the MII_SPEED value
> + *     @node:  device node
> + *
> + *     Returns the MII_SPEED value for MPC512x and MPC52xx systems.
> + *     The value gets computed such that the resulting MDC frequency
> + *     is 2.5 MHz or lower.
> + */
> +
> +int
> +mpc5xxx_get_mii_speed(struct of_device *ofdev)
> +{
> +       unsigned int clock, speed;
> +
> +       clock = mpc5xxx_get_bus_frequency(ofdev->node);
> +
> +       if (!clock) {
> +               dev_err(&ofdev->dev, "could not determine IPS/IPB clock\n");
> +               return -ENODEV;
> +       }
> +
> +       /* scale for a MII clock <= 2.5 MHz */
> +       speed = (clock + 2499999) / 2500000;
> +
> +       /* only 6 bits available for MII speed */
> +       if (speed > 0x3F) {
> +               speed = 0x3F;
> +               dev_err(&ofdev->dev,
> +                       "MII clock (%d MHz) exceeds max (2.5 MHz)\n",
> +                       clock / speed);
> +       }
> +
> +       /* Field is in bits 25:30 of MII_SPEED register */
> +       return speed << 1;
> +}
> +EXPORT_SYMBOL(mpc5xxx_get_mii_speed);
> diff --git a/drivers/net/fs_enet/mii-fec.c b/drivers/net/fs_enet/mii-fec.c
> index 75a0999..a28d39f 100644
> --- a/drivers/net/fs_enet/mii-fec.c
> +++ b/drivers/net/fs_enet/mii-fec.c
> @@ -36,6 +36,7 @@
>  #include <asm/pgtable.h>
>  #include <asm/irq.h>
>  #include <asm/uaccess.h>
> +#include <asm/mpc5xxx.h>
>
>  #include "fs_enet.h"
>  #include "fec.h"
> @@ -103,7 +104,6 @@ static int fs_enet_fec_mii_reset(struct mii_bus *bus)
>  static int __devinit fs_enet_mdio_probe(struct of_device *ofdev,
>                                         const struct of_device_id *match)
>  {
> -       struct device_node *np = NULL;
>        struct resource res;
>        struct mii_bus *new_bus;
>        struct fec_info *fec;
> @@ -133,13 +133,20 @@ static int __devinit fs_enet_mdio_probe(struct of_device *ofdev,
>        if (!fec->fecp)
>                goto out_fec;
>
> -       fec->mii_speed = ((ppc_proc_freq + 4999999) / 5000000) << 1;
> +       if (of_device_is_compatible(ofdev->node, "fsl,mpc5121-fec-mdio")) {
> +               i = mpc5xxx_get_mii_speed(ofdev);
> +               if (i < 0)
> +                       goto out_unmap_regs;
> +               fec->mii_speed = i;
> +       } else {
> +               fec->mii_speed = ((ppc_proc_freq + 4999999) / 5000000) << 1;
> +       }
>
>        setbits32(&fec->fecp->fec_r_cntrl, FEC_RCNTRL_MII_MODE);
>        setbits32(&fec->fecp->fec_ecntrl, FEC_ECNTRL_PINMUX |
>                                          FEC_ECNTRL_ETHER_EN);
>        out_be32(&fec->fecp->fec_ievent, FEC_ENET_MII);
> -       out_be32(&fec->fecp->fec_mii_speed, fec->mii_speed);
> +       clrsetbits_be32(&fec->fecp->fec_mii_speed, 0x7E, fec->mii_speed);
>
>        new_bus->phy_mask = ~0;
>        new_bus->irq = kmalloc(sizeof(int) * PHY_MAX_ADDR, GFP_KERNEL);
> --
> 1.6.0.6
>
>



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.