From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bryan Wu Subject: Re: [PATCH 1/2] netdev/fec: fix performance impact from mdio poll operation Date: Sat, 08 May 2010 18:07:30 +0800 Message-ID: <4BE537E2.6010809@canonical.com> References: <1273199239-11057-1-git-send-email-bryan.wu@canonical.com> <1273199239-11057-2-git-send-email-bryan.wu@canonical.com> Reply-To: bryan.wu@canonical.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "davem@davemloft.net" , Sascha Hauer , Greg Ungerer , Amit Kucheria , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Andy Fleming Return-path: Received: from adelie.canonical.com ([91.189.90.139]:47125 "EHLO adelie.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752426Ab0EHKIA (ORCPT ); Sat, 8 May 2010 06:08:00 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 05/08/2010 12:06 AM, Andy Fleming wrote: > On Thursday, May 6, 2010, Bryan Wu wrote: >> BugLink: http://bugs.launchpad.net/bugs/546649 >> BugLink: http://bugs.launchpad.net/bugs/457878 >> >> After introducing phylib supporting, users experienced performace drop. That is >> because of the mdio polling operation of phylib. Use msleep to replace the busy >> waiting cpu_relax() and remove the warning message. > > I'm a little confused by this patch. In order to improve performance, > you made the mdio functions fail silently? Why are you getting > timeouts at all? From the BugLink, we experienced a lot of error message about mdio_read timeout. Actually, the logical in this function is quite simple and I still have no idea about why mdio_read timeout. That might be hardware defect. > The Phy lib is not going to respond well if an mdio > write times out without returning an error. And returning an error > means the whole state machine has to reset, as a failed write is not > something we currently handle gracefully. > Right, if we return error to phylib due to mdio read times out, the performance will drop a lot. > Is it possible to use an interrupt to get the phy state change? This > would allow the phy lib to stop its incessant polling. It doesn't > solve the question of why it's timing out, though. > I'm going to try the interrupt, but fec driver is shared by several SoCs. It might be a little complicated and still cannot fix the timing out issue. Is there any example driver to use an interrupt to get the phy state change? Thanks, -Bryan >> >> Signed-off-by: Bryan Wu >> Acked-by: Andy Whitcroft >> --- >> drivers/net/fec.c | 45 +++++++++++++++++++++------------------------ >> 1 files changed, 21 insertions(+), 24 deletions(-) >> >> diff --git a/drivers/net/fec.c b/drivers/net/fec.c >> index 2b1651a..9c58f6b 100644 >> --- a/drivers/net/fec.c >> +++ b/drivers/net/fec.c >> @@ -203,7 +203,7 @@ static void fec_stop(struct net_device *dev); >> #define FEC_MMFR_TA (2<< 16) >> #define FEC_MMFR_DATA(v) (v& 0xffff) >> >> -#define FEC_MII_TIMEOUT 10000 >> +#define FEC_MII_TIMEOUT 10 >> >> /* Transmitter timeout */ >> #define TX_TIMEOUT (2 * HZ) >> @@ -611,13 +611,29 @@ spin_unlock: >> /* >> * NOTE: a MII transaction is during around 25 us, so polling it... >> */ >> -static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum) >> +static int fec_enet_mdio_poll(struct fec_enet_private *fep) >> { >> - struct fec_enet_private *fep = bus->priv; >> int timeout = FEC_MII_TIMEOUT; >> >> fep->mii_timeout = 0; >> >> + /* wait for end of transfer */ >> + while (!(readl(fep->hwp + FEC_IEVENT)& FEC_ENET_MII)) { >> + msleep(1); >> + if (timeout--< 0) { >> + fep->mii_timeout = 1; >> + break; >> + } >> + } >> + >> + return 0; >> +} >> + >> +static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum) >> +{ >> + struct fec_enet_private *fep = bus->priv; >> + >> + >> /* clear MII end of transfer bit*/ >> writel(FEC_ENET_MII, fep->hwp + FEC_IEVENT); >> >> @@ -626,15 +642,7 @@ static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum) >> FEC_MMFR_PA(mii_id) | FEC_MMFR_RA(regnum) | >> FEC_MMFR_TA, fep->hwp + FEC_MII_DATA); >> >> - /* wait for end of transfer */ >> - while (!(readl(fep->hwp + FEC_IEVENT)& FEC_ENET_MII)) { >> - cpu_relax(); >> - if (timeout--< 0) { >> - fep->mii_timeout = 1; >> - printk(KERN_ERR "FEC: MDIO read timeout\n"); >> - return -ETIMEDOUT; >> - } >> - } >> + fec_enet_mdio_poll(fep); >> >> /* return value */ >> return FEC_MMFR_DATA(readl(fep->hwp + FEC_MII_DATA)); >> @@ -644,9 +652,6 @@ static int fec_enet_mdio_write(struct mii_bus *bus, int mii_id, int regnum, >> u16 value) >> { >> struct fec_enet_private *fep = bus->priv; >> - int timeout = FEC_MII_TIMEOUT; >> - >> - fep->mii_timeout = 0; >> >> /* clear MII end of transfer bit*/ >> writel(FEC_ENET_MII, fep->hwp + FEC_IEVENT); >> @@ -657,15 +662,7 @@ static int fec_enet_mdio_write(struct mii_bus *bus, int mii_id, int regnum, >> FEC_MMFR_TA | FEC_MMFR_DATA(value), >> fep->hwp + FEC_MII_DATA); >> >> - /* wait for end of transfer */ >> - while (!(readl(fep->hwp + FEC_IEVENT)& FEC_ENET_MII)) { >> - cpu_relax(); >> - if (timeout--< 0) { >> - fep->mii_timeout = 1; >> - printk(KERN_ERR "FEC: MDIO write timeout\n"); >> - return -ETIMEDOUT; >> - } >> - } >> + fec_enet_mdio_poll(fep); >> >> return 0; >> } >> -- >> 1.7.0.1 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe netdev" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >