From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nishanth Menon Subject: Re: [PATCH] OMAP3: I2C: Errata i207: Clear wrong RDR interrupt Date: Thu, 1 Apr 2010 08:53:04 -0500 Message-ID: <4BB4A540.9080000@ti.com> References: <1270124427-11208-1-git-send-email-manjugk@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1270124427-11208-1-git-send-email-manjugk-l0cyMroinI0@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "G, Manjunath Kondaiah" Cc: "ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org" , "linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "Kalliguddi, Hema" List-Id: linux-i2c@vger.kernel.org G, Manjunath Kondaiah had written, on 04/01/2010 07:20 AM, the following: > Under certain rare conditions, I2C_STAT[13].RDR bit may be set > and the corresponding interrupt fire, even there is no data in > the receive FIFO, or the I2C data transfer is still ongoing. > These spurious RDR events must be ignored by the software. > > This patch handles and ignores RDR spurious interrupts. > > Reviewed-by: Kalliguddi, Hema > Signed-off-by: Manjunatha GK > Cc: linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > Cc: ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org > Cc: Kalliguddi, Hema > --- > drivers/i2c/busses/i2c-omap.c | 13 +++++++++++++ > 1 files changed, 13 insertions(+), 0 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c > index f2019d2..acf4076 100644 > --- a/drivers/i2c/busses/i2c-omap.c > +++ b/drivers/i2c/busses/i2c-omap.c > @@ -796,6 +796,19 @@ complete: > } > if (stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) { > u8 num_bytes = 1; > + > + /* > + * OMAP3 I2C Errata ID: i207 > + * Under certain rare conditions, RDR could be set again > + * when the bus is busy, then clear and ignore the interrupt > + */ > + if (!(stat & OMAP_I2C_STAT_RRDY) && (stat & > + OMAP_I2C_STAT_BB)) { > + /* clear RDR */ > + omap_i2c_ack_stat(dev, stat & OMAP_I2C_STAT_RDR); > + dev_err(dev->dev, "I2C: RDR when bus is busy.\n"); > + return IRQ_HANDLED; > + } couple of comments after reading thru the errata: a) the sequence in the errata doc is: if (stat & OMAP_I2C_STAT_RDR) { /* This is cleaner that using an obtuse check using !(stat & OMAP_I2C_STAT_RRDY) */ omap_i2c_ack_stat(dev, stat & OMAP_I2C_STAT_RDR); /* dummy read - i think this needs clarification as to why */ if (omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG) & OMAP_I2C_STAT_BB) /* reason for the i2c_read_reg is because errata mentions a dummy stat read which might mean something for BB -> I am not sure may need to be checked with H/w team. */ continue; /* recheck - faster response compared to return and re generate interrupt */ } b) does this apply to OMAP2 and OMAP4? (unrelated sidenote: my usual crib: we probably need an errata management system soon considering the erratas that are getting workedaround in code.. :( ).. > if (dev->fifo_size) { > if (stat & OMAP_I2C_STAT_RRDY) > num_bytes = dev->fifo_size; -- Regards, Nishanth Menon