[PATCH 2/2 v2] MPC52xx FEC: be more conservative when setting MII_SPEED register
Grant Likely
grant.likely at secretlab.ca
Fri Jul 17 08:48:08 EST 2009
On Thu, Jul 16, 2009 at 3:42 PM, Wolfgang Denk<wd at denx.de> wrote:
> This patch adds error checking and prevents clobbering unrelated bits
> (reserved bits or the DIS_PREAMBLE bit) when writing the MII_SPEED
> register on MPC52xx systems.
>
> Signed-off-by: Wolfgang Denk <wd at denx.de>
> Cc: Grant Likely <grant.likely at secretlab.ca>
> Cc: Kumar Gala <galak at kernel.crashing.org>
> Cc: <netdev at vger.kernel.org>
Mostly good. One comment below. When it's resolved, feel free to add
my acked-by line. Thanks for getting this done.
> @@ -105,8 +105,23 @@ static int mpc52xx_fec_mdio_probe(struct of_device *of,
> dev_set_drvdata(dev, bus);
>
> /* set MII speed */
> - out_be32(&priv->regs->mii_speed,
> - ((mpc5xxx_get_bus_frequency(of->node) >> 20) / 5) << 1);
> + clock = mpc5xxx_get_bus_frequency(of->node);
> + if (!clock) {
> + dev_err(&of->dev, "could not determine IPS/IPB clock\n");
> + goto out_unmap;
> + }
Just thought of something. If it cannot find the clock, then wouldn't
it be better to just use the maximum divider and print a warning
instead of bailing completely? This goes for the other patch as well.
> +
> + /* scale for a MII clock <= 2.5 MHz */
> + speed = (clock + 2499999) / 2500000;
> +
> + /* only 6 bits (25:30) available for MII speed */
> + if (speed > 0x3F) {
> + speed = 0x3F;
> + dev_err(&of->dev, "MII clock (%d Hz) exceeds max (2.5 MHz)\n",
> + clock / speed);
> + }
> +
> + clrsetbits_be32(&priv->regs->mii_speed, 0x7E, speed << 1);
>
> err = of_mdiobus_register(bus, np);
> if (err)
> --
> 1.6.0.6
>
>
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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