G, Manjunath Kondaiah had written, on 04/27/2010 09:47 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.
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@xxxxxx>
Cc: linux-i2c@xxxxxxxxxxxxxxx
Cc: ben-linux@xxxxxxxxx
Cc: Kalliguddi, Hema <hemahk@xxxxxx>
Cc: Nishanth Menon <nm@xxxxxx>
Cc: Aaro Koskinen <Aaro.Koskinen@xxxxxxxxx>
Cc: Tony Lindgren <tony@xxxxxxxxxxx>
---
drivers/i2c/busses/i2c-omap.c | 39 +++++++++++++++++++++++++++++++++++++++
1 files changed, 39 insertions(+), 0 deletions(-)
diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index ef73483..f232f96 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -199,6 +199,7 @@ struct omap_i2c_dev {
u16 bufstate;
u16 syscstate;
u16 westate;
+ bool errata_i207;
Just my 2cents:
Could we use a u32 quirk? this will allow multiple similar quirks
(already existing in the driver to use this mechanism)
and
#define OMAP_I2C_QUIRK_i207 0x1
/* we can add more quirks here and cleanup the i2c driver quiet a bit */
#define IS_OMAP_I2C_QUIRK(d,q) ((d)->q & quirk)
};
const static u8 reg_map[] = {
@@ -498,6 +499,12 @@ 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_i207 = false;
+
+ if (cpu_is_omap2430() || cpu_is_omap34xx()) {
+ dev->errata_i207 = true;
+ }
oneliner with {}? did you run checkpatch.pl?
+
/* Enable interrupts */
dev->iestate = (OMAP_I2C_IE_XRDY | OMAP_I2C_IE_RRDY |
OMAP_I2C_IE_ARDY | OMAP_I2C_IE_NACK |
@@ -695,6 +702,34 @@ 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 the bus is busy.\n");
+ }
+
+ }
+ }
+}
+
/* rev1 devices are apparently only on some 15xx */
#ifdef CONFIG_ARCH_OMAP15XX
@@ -826,6 +861,10 @@ complete:
}
if (stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) {
u8 num_bytes = 1;
+
+ if (dev->errata_i207)
+ i2c_omap_errata_i207(dev, stat);
+
if (dev->fifo_size) {
if (stat & OMAP_I2C_STAT_RRDY)
num_bytes = dev->fifo_size;
looks good overall.. thanks..
--
Regards,
Nishanth Menon
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