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|
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -283,7 +283,7 @@ comment "I2C system bus drivers (mostly
config I2C_AT91
tristate "Atmel AT91 I2C Two-Wire interface (TWI)"
- depends on ARCH_AT91 && EXPERIMENTAL && BROKEN
+ depends on ARCH_AT91 && EXPERIMENTAL
help
This supports the use of the I2C interface on Atmel AT91
processors.
--- a/drivers/i2c/busses/i2c-at91.c
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -11,8 +11,18 @@
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
+
+ D. Gilbert [20100318 AT91SAM9G20]
+ - Check for NACK, a NACK will abort current tranfser,
+ returned as errno=EREMOTEIO unless I2C_M_IGNORE_NAK is set
+ - Only supports 7 bit I2C device (slave) address
+ - clockrate adjustable (module_param).
*/
+
+/* Uncomment following line to see dev_dbg() output in logs */
+/* #define DEBUG 1 */
+
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/err.h>
@@ -32,26 +42,28 @@
#define TWI_CLOCK 100000 /* Hz. max 400 Kbits/sec */
+static unsigned int clockrate = TWI_CLOCK;
+static unsigned int prev_clockrate = TWI_CLOCK;
static struct clk *twi_clk;
static void __iomem *twi_base;
#define at91_twi_read(reg) __raw_readl(twi_base + (reg))
#define at91_twi_write(reg, val) __raw_writel((val), twi_base + (reg))
-
/*
- * Initialize the TWI hardware registers.
+ * Set TWI clock dividers based on clockrate (clock rate for SCL)
*/
-static void __devinit at91_twi_hwinit(void)
+static void at91_twi_clock_dividers(void)
{
unsigned long cdiv, ckdiv;
- at91_twi_write(AT91_TWI_IDR, 0xffffffff); /* Disable all interrupts */
- at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST); /* Reset peripheral */
- at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN); /* Set Master mode */
+ if (clockrate < 1000)
+ clockrate = 1000;
+ else if (clockrate > 400000)
+ clockrate = 400000;
- /* Calcuate clock dividers */
- cdiv = (clk_get_rate(twi_clk) / (2 * TWI_CLOCK)) - 3;
+ /* Calculate clock dividers */
+ cdiv = (clk_get_rate(twi_clk) / (2 * clockrate)) - 3;
cdiv = cdiv + 1; /* round up */
ckdiv = 0;
while (cdiv > 255) {
@@ -61,41 +73,92 @@ static void __devinit at91_twi_hwinit(vo
if (cpu_is_at91rm9200()) { /* AT91RM9200 Errata #22 */
if (ckdiv > 5) {
- printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value!\n");
+ printk(KERN_ERR "i2c-at91: Invalid AT91RM9200 clock rate\n");
ckdiv = 5;
}
}
+ /* AT91SAM9G20 has 3 bits for ckdiv so it cannot exceed 7 */
+ if (cpu_is_at91sam9g20()) {
+ if (ckdiv > 7) {
+ printk(KERN_ERR "i2c-at91: Invalid AT91SAM9G20 clock "
+ "rate, ckdiv=%lu\n", ckdiv);
+ ckdiv = 7;
+ }
+ }
at91_twi_write(AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv);
+ prev_clockrate = clockrate;
}
/*
- * Poll the i2c status register until the specified bit is set.
- * Returns 0 if timed out (100 msec).
+ * Initialize the TWI hardware registers.
*/
-static short at91_poll_status(unsigned long bit)
+static void __devinit at91_twi_hwinit(void)
{
- int loop_cntr = 10000;
+ at91_twi_write(AT91_TWI_IDR, 0xffffffff); /* Disable all interrupts */
+ at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST); /* Reset peripheral */
+ /* Set Master mode; Atmel suggests disabling slave mode */
+ at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN | AT91_TWI_SVDIS);
+ at91_twi_clock_dividers();
+}
+
+/*
+ * Poll the i2c status register until the specified bit is set or a NACK
+ * occurs. Returns 0 if timed out (50 msec). If nack_seen_p is non-NULL
+ * then write 0 to it first, then if the NACK bit is set in the status
+ * register then write 1 to it and immediately return with a value of 1.
+ */
+static short at91_poll_status(unsigned long bit, int * nack_seen_p)
+{
+ int loop_cntr = 5000;
+ unsigned long stat;
+
+ if (nack_seen_p)
+ *nack_seen_p = 0;
+ if (clockrate <= 20000)
+ loop_cntr = 100;
do {
- udelay(10);
- } while (!(at91_twi_read(AT91_TWI_SR) & bit) && (--loop_cntr > 0));
+ if (clockrate <= 20000)
+ udelay(100);
+ else if (clockrate <= 100000)
+ udelay(10);
+ else
+ udelay(3);
+ stat = at91_twi_read(AT91_TWI_SR);
+ if ((stat & AT91_TWI_NACK) && nack_seen_p) {
+ *nack_seen_p = 1;
+ return 1;
+ }
+ } while (!(stat & bit) && (--loop_cntr > 0));
return (loop_cntr > 0);
}
static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length)
{
+ int nack_seen = 0;
+ int sent_stop = 0;
+
/* Send Start */
- at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
+ if (1 == length) {
+ at91_twi_write(AT91_TWI_CR, AT91_TWI_START | AT91_TWI_STOP);
+ sent_stop = 1;
+ } else
+ at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
/* Read data */
while (length--) {
- if (!length) /* need to send Stop before reading last byte */
+ /* send Stop before reading last byte (if not already done) */
+ if ((0 == length) && (0 == sent_stop))
at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
- if (!at91_poll_status(AT91_TWI_RXRDY)) {
+ if (!at91_poll_status(AT91_TWI_RXRDY, &nack_seen)) {
dev_dbg(&adap->dev, "RXRDY timeout\n");
return -ETIMEDOUT;
+ } else if (nack_seen) {
+ dev_dbg(&adap->dev, "read NACKed\n");
+ /* NACK supplies Stop */
+ return -EREMOTEIO;
}
*buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff);
}
@@ -105,16 +168,24 @@ static int xfer_read(struct i2c_adapter
static int xfer_write(struct i2c_adapter *adap, unsigned char *buf, int length)
{
+ int nack_seen = 0;
+
/* Load first byte into transmitter */
at91_twi_write(AT91_TWI_THR, *buf++);
- /* Send Start */
+ /* Send Start [AT91SAM9G20 does not need this on write] */
at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
do {
- if (!at91_poll_status(AT91_TWI_TXRDY)) {
+ if (!at91_poll_status(AT91_TWI_TXRDY, &nack_seen)) {
dev_dbg(&adap->dev, "TXRDY timeout\n");
+ /* Set Master mode again */
+ at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN);
return -ETIMEDOUT;
+ } else if (nack_seen) {
+ dev_dbg(&adap->dev, "write NACKed\n");
+ /* NACK supplies Stop */
+ return -EREMOTEIO;
}
length--; /* byte was transmitted */
@@ -123,7 +194,7 @@ static int xfer_write(struct i2c_adapter
at91_twi_write(AT91_TWI_THR, *buf++);
} while (length);
- /* Send Stop */
+ /* Send Stop [AT91SAM9G20 does not need this on write] */
at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
return 0;
@@ -136,11 +207,19 @@ static int xfer_write(struct i2c_adapter
* Instead the "internal device address" has to be written using a separate
* i2c message.
* http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
+ * [dpg] By 2010 silicon bugs should be fixed, will need IADR for 10 bit device address
*/
static int at91_xfer(struct i2c_adapter *adap, struct i2c_msg *pmsg, int num)
{
int i, ret;
+ int nack_seen = 0;
+ if (prev_clockrate != clockrate) {
+ dev_dbg(&adap->dev, "at91_xfer: prev_clockrate=%u "
+ "clockrate=%u, change\n", prev_clockrate, clockrate);
+ at91_twi_clock_dividers();
+ msleep(1); /* let things settle */
+ }
dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
for (i = 0; i < num; i++) {
@@ -158,13 +237,23 @@ static int at91_xfer(struct i2c_adapter
else
ret = xfer_write(adap, pmsg->buf, pmsg->len);
- if (ret)
- return ret;
-
+ if (ret) {
+ if ((I2C_M_IGNORE_NAK & pmsg->flags) &&
+ (-EREMOTEIO == ret)) {
+ dev_dbg(&adap->dev, "transfer "
+ "NACKed, skip to next\n");
+ pmsg++;
+ continue;
+ } else
+ return ret;
+ }
/* Wait until transfer is finished */
- if (!at91_poll_status(AT91_TWI_TXCOMP)) {
+ if (!at91_poll_status(AT91_TWI_TXCOMP, &nack_seen)) {
dev_dbg(&adap->dev, "TXCOMP timeout\n");
return -ETIMEDOUT;
+ } else if (nack_seen) {
+ dev_dbg(&adap->dev, "TXCOMP NACKed\n");
+ return -EREMOTEIO;
}
}
dev_dbg(&adap->dev, "transfer complete\n");
@@ -239,7 +328,8 @@ static int __devinit at91_i2c_probe(stru
goto fail3;
}
- dev_info(&pdev->dev, "AT91 i2c bus driver.\n");
+ dev_info(&pdev->dev, "AT91 TWI (I2C) bus driver [SCL %d Hz]\n",
+ clockrate);
return 0;
fail3:
@@ -295,6 +385,11 @@ static int at91_i2c_resume(struct platfo
#define at91_i2c_resume NULL
#endif
+/* I2C clock speed, in Hz 0-400kHz*/
+module_param(clockrate, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(clockrate,
+ "SCL clock rate, 1000 to 400000 Hz (def: 100 kHz)");
+
/* work with "modprobe at91_i2c" from hotplugging or coldplugging */
MODULE_ALIAS("platform:at91_i2c");
@@ -323,5 +418,5 @@ module_init(at91_i2c_init);
module_exit(at91_i2c_exit);
MODULE_AUTHOR("Rick Bronson");
-MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
+MODULE_DESCRIPTION("I2C (TWI) master driver for Atmel AT91");
MODULE_LICENSE("GPL");
|
