From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out001.atlarge.net (out001.atlarge.net [129.41.63.69]) by ozlabs.org (Postfix) with ESMTP id 228A8DDE46 for ; Wed, 11 Jul 2007 15:49:27 +1000 (EST) Date: Wed, 11 Jul 2007 07:49:23 +0200 From: Domen Puncer To: Jean Delvare Subject: Re: [PATCH] i2c-mpc: work around missing-9th-clock-pulse bug Message-ID: <20070711054923.GA4375@moe.telargo.com> References: <20070709071955.GD4186@moe.telargo.com> <20070710061736.GG4186@moe.telargo.com> <20070710144030.3786cbf3@hyperion.delvare> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20070710144030.3786cbf3@hyperion.delvare> Cc: i2c@lm-sensors.org, linuxppc-embedded@ozlabs.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 10/07/07 14:40 +0200, Jean Delvare wrote: > Hi Grant, hi Domen, > > On Tue, 10 Jul 2007 00:22:05 -0600, Grant Likely wrote: > > On 7/10/07, Domen Puncer wrote: > > > Work around a problem reported on: > > > http://ozlabs.org/pipermail/linuxppc-embedded/2005-July/019038.html > > > Without this patch I2C on mpc5200 becomes unusable after a while. > > > Tested on mpc5200 boards by Matthias and me. > > > > > > > > > Signed-off-by: Domen Puncer > > > > Looks good to me, > > > > Acked-by: Grant Likely > > OK, I will take this patch, but I'd like you to add a comment before > mpc_i2c_fixup() explaining what exactly the problem is and how it is > worked around. Otherwise it's a bit obscure what is going on. OK. > > I guess you want this patch in 2.6.23-rc1? Yes. So... v3: <----------- cut -------------> Work around a problem reported on: http://ozlabs.org/pipermail/linuxppc-embedded/2005-July/019038.html Without this patch I2C on mpc5200 becomes unusable after a while. Tested on mpc5200 boards by Matthias Fechner and me. Signed-off-by: Domen Puncer --- drivers/i2c/busses/i2c-mpc.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) Index: work-powerpc.git/drivers/i2c/busses/i2c-mpc.c =================================================================== --- work-powerpc.git.orig/drivers/i2c/busses/i2c-mpc.c +++ work-powerpc.git/drivers/i2c/busses/i2c-mpc.c @@ -74,6 +74,24 @@ static irqreturn_t mpc_i2c_isr(int irq, return IRQ_HANDLED; } +/* Sometimes 9th clock pulse isn't generated, so slave doesn't release + * the bus. Documented and suggested workaround on + * http://ozlabs.org/pipermail/linuxppc-embedded/2005-July/019038.html + */ +static void mpc_i2c_fixup(struct mpc_i2c *i2c) +{ + writeccr(i2c, 0); + udelay(30); + writeccr(i2c, CCR_MEN); + udelay(30); + writeccr(i2c, CCR_MSTA | CCR_MTX); + udelay(30); + writeccr(i2c, CCR_MSTA | CCR_MTX | CCR_MEN); + udelay(30); + writeccr(i2c, CCR_MEN); + udelay(30); +} + static int i2c_wait(struct mpc_i2c *i2c, unsigned timeout, int writing) { unsigned long orig_jiffies = jiffies; @@ -153,6 +171,7 @@ static void mpc_i2c_start(struct mpc_i2c static void mpc_i2c_stop(struct mpc_i2c *i2c) { writeccr(i2c, CCR_MEN); + writeccr(i2c, 0); } static int mpc_write(struct mpc_i2c *i2c, int target, @@ -245,6 +264,8 @@ static int mpc_xfer(struct i2c_adapter * } if (time_after(jiffies, orig_jiffies + HZ)) { pr_debug("I2C: timeout\n"); + if (readb(i2c->base + MPC_I2C_SR) == (CSR_MCF | CSR_MBB | CSR_RXAK)) + mpc_i2c_fixup(i2c); return -EIO; } schedule();