netdev - Re: [PATCH 3/4] net/fec: set phy_speed to the optimal frequency 2.5 MHz

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Date:	Tue, 20 Sep 2011 10:57:01 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Troy Kisky <troy.kisky@...ndarydevices.com>
CC:	Shawn Guo <shawn.guo@...aro.org>, <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	<linux-arm-kernel@...ts.infradead.org>, <patches@...aro.org>
Subject: Re: [PATCH 3/4] net/fec: set phy_speed to the optimal frequency 2.5
 MHz

On Mon, Sep 19, 2011 at 03:39:30PM -0700, Troy Kisky wrote:
> On 9/18/2011 4:54 AM, Shawn Guo wrote:
> >With the unnecessary 1 bit left-shift on fep->phy_speed during the
> >calculation, the phy_speed always runs at the half frequency of the
> >optimal one 2.5 MHz.
> >
> >The patch removes that 1 bit left-shift to get the optimal phy_speed.
> >
> >Signed-off-by: Shawn Guo<shawn.guo@...aro.org>
> >---
> >  drivers/net/fec.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> >diff --git a/drivers/net/fec.c b/drivers/net/fec.c
> >index 5ef0e34..04206e4 100644
> >--- a/drivers/net/fec.c
> >+++ b/drivers/net/fec.c
> >@@ -1007,7 +1007,7 @@ static int fec_enet_mii_init(struct platform_device *pdev)
> >  	/*
> >  	 * Set MII speed to 2.5 MHz (= clk_get_rate() / 2 * phy_speed)
> >  	 */
> >-	fep->phy_speed = DIV_ROUND_UP(clk_get_rate(fep->clk), 5000000)<<  1;
> >+	fep->phy_speed = DIV_ROUND_UP(clk_get_rate(fep->clk), 5000000);
> >  	writel(fep->phy_speed, fep->hwp + FEC_MII_SPEED);
> >
> >  	fep->mii_bus = mdiobus_alloc();
> Do you need to round up to an even value? Is the hardware
> documentation wrong?

The round up is something existed, and the patch does not touch that
part.

> Does this need a quirk? What boards has this been verified to fix?
> 

I tested this on i.mx28, i.mx53 and i.mx6q.  Do you see problem on
your platform?

-- 
Regards,
Shawn

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