RE: [PATCH v6] OMAP2/3: I2C: Errata ID i207: Clear wrong RDR interrupt

G, Manjunath Kondaiah
2010-04-28T10:20:22Z

> -----Original Message-----
> From: Menon, Nishanth
> Sent: Wednesday, April 28, 2010 3:35 PM
> 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
> Subject: Re: [PATCH v6] OMAP2/3: I2C: Errata ID i207: Clear
> wrong RDR interrupt
>
> 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<manjugk-l0cyMroinI0@public.gmane.org>
> > Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> > Cc: ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org
> > Cc: Kalliguddi, Hema<hemahk-l0cyMroinI0@public.gmane.org>
> > Cc: Nishanth Menon<nm-l0cyMroinI0@public.gmane.org>
> > Cc: Aaro Koskinen<Aaro.Koskinen-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org>
> > Cc: Tony Lindgren<tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
> > ---
> > 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<</1 << (need a space)
> >
> > 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.

This errata is not applicable for 2420 and it is applicable for:
1. omap2430
2. omap34xx(including omap3630).

Sorry. My earlier patch was using this errata logic for all omap's
except omap4 which was wrong(for omap2420 and omap1 - not sure, I don't have
any data hence ignoring this errata for omap1 also).

>
> > + 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
> --
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