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

Nishanth Menon
2010-04-28T10:05:27Z

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.

> + 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