From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nishanth Menon Subject: Re: [PATCH v6] OMAP2/3: I2C: Errata ID i207: Clear wrong RDR interrupt Date: Wed, 28 Apr 2010 05:05:27 -0500 Message-ID: <4BD80867.7020801@ti.com> References: <1272433677-28658-1-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: <1272433677-28658-1-git-send-email-manjugk-l0cyMroinI0@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "G, Manjunath Kondaiah" Cc: "linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org" , "Kalliguddi, Hema" , Aaro Koskinen , Tony Lindgren List-Id: linux-i2c@vger.kernel.org very minor comments below: On 04/28/2010 12:47 AM, G, Manjunath Kondaiah wrote: > 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. > > The below sequence is required in interrupt handler for > handling this errata: > 1. If RDR is set to 1, clear RDR > 2. Read I2C status register and check for BusBusy bit. If BusBusy > bit is set, skip remaining steps. > 3. If BusBusy bit is not set, perform read operation on I2C status > register. > 4. If RDR is set, clear the same. Check RDR again and clear if it sets > RDR bit again. > 5. Perform I2C Data Read operation N number of times(where N is value > read from the register BUFSTAT-RXSTAT bit fields). > > Note : This errata is applicable for OMAP2 and OMAP3 platforms only. > It is not applicable for OMAP4. > > Signed-off-by: Manjunatha GK > Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > Cc: ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org > Cc: Kalliguddi, Hema > Cc: Nishanth Menon > Cc: Aaro Koskinen > Cc: Tony Lindgren > --- > drivers/i2c/busses/i2c-omap.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 40 insertions(+), 0 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c > index ef73483..cdcdfeb 100644 > --- a/drivers/i2c/busses/i2c-omap.c > +++ b/drivers/i2c/busses/i2c-omap.c > @@ -166,6 +166,8 @@ enum { > #define SYSC_IDLEMODE_SMART 0x2 > #define SYSC_CLOCKACTIVITY_FCLK 0x2 > > +/* Errata definitions */ > +#define I2C_OMAP_ERRATA_I207 (1<< 0) ^^^^ tiny nit: s/1< > struct omap_i2c_dev { > struct device *dev; > @@ -199,6 +201,7 @@ struct omap_i2c_dev { > u16 bufstate; > u16 syscstate; > u16 westate; > + u16 errata; overall I'd prefer the term quirk over errata - quirk is more of a standard linux term used accross network, usb and other drivers, will allow the code to be a little more familiar with the upstream maintainers/reviewers.. but i leave it to tony and others to comment more.. maybe it is just me being an ass again ;) > }; > > const static u8 reg_map[] = { > @@ -498,6 +501,11 @@ static int omap_i2c_init(struct omap_i2c_dev *dev) > /* Take the I2C module out of reset: */ > omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN); > > + dev->errata = 0; > + > + if (cpu_is_omap2430() || cpu_is_omap34xx()) ^^^^^^^^ wont cpu_is_omap24xx() cover omap2420 as well? I think it might be better using that.. apologies on missing it in the last look. > + dev->errata |= I2C_OMAP_ERRATA_I207; > + > /* Enable interrupts */ > dev->iestate = (OMAP_I2C_IE_XRDY | OMAP_I2C_IE_RRDY | > OMAP_I2C_IE_ARDY | OMAP_I2C_IE_NACK | > @@ -695,6 +703,34 @@ omap_i2c_ack_stat(struct omap_i2c_dev *dev, u16 stat) > omap_i2c_write_reg(dev, OMAP_I2C_STAT_REG, stat); > } > > +static inline void i2c_omap_errata_i207(struct omap_i2c_dev *dev, u16 stat) > +{ > + /* > + * I2C Errata(Errata Nos. OMAP2: 1.67, OMAP3: 1.8) > + * Not applicable for OMAP4. > + * Under certain rare conditions, RDR could be set again > + * when the bus is busy, then ignore the interrupt and > + * clear the interrupt. > + */ > + if (stat& OMAP_I2C_STAT_RDR) { > + /* Step 1: If RDR is set, clear it */ > + omap_i2c_ack_stat(dev, OMAP_I2C_STAT_RDR); > + > + /* Step 2: */ > + if (!(omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG) > + & OMAP_I2C_STAT_BB)) { > + > + /* Step 3: */ > + if (omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG) > + & OMAP_I2C_STAT_RDR) { > + omap_i2c_ack_stat(dev, OMAP_I2C_STAT_RDR); > + dev_dbg(dev->dev, "RDR when bus is busy.\n"); > + } > + > + } > + } > +} > + > /* rev1 devices are apparently only on some 15xx */ > #ifdef CONFIG_ARCH_OMAP15XX > > @@ -826,6 +862,10 @@ complete: > } > if (stat& (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) { > u8 num_bytes = 1; > + > + if (dev->errata& I2C_OMAP_ERRATA_I207) > + i2c_omap_errata_i207(dev, stat); > + > if (dev->fifo_size) { > if (stat& OMAP_I2C_STAT_RRDY) > num_bytes = dev->fifo_size; Thanks, sparse and checkpatch are happy now :) Regards, Nishanth Menon