Re: [PATCH] I2C update for 2.6.8-rc1

Greg KH
2004-07-15T00:18:58Z

ChangeSet 1.1784.13.2, 2004/07/08 16:06:22-07:00, ebs@ebshome.net

[PATCH] I2C PPC4xx IIC driver: 0-length transactions bit-banging implementation

IBM PPC 4xx i2c controller doesn't support 0-length transactions (e.g. used by
SMBUS_QUICK). This patch implements bit-banging emulation for such requests and
removes temporary kludge added earlier.

Signed-off-by: Eugene Surovegin <ebs@ebshome.net>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/i2c/busses/i2c-ibm_iic.c | 132 +++++++++++++++++++++++++++++++++++++--
1 files changed, 126 insertions(+), 6 deletions(-)

diff -Nru a/drivers/i2c/busses/i2c-ibm_iic.c b/drivers/i2c/busses/i2c-ibm_iic.c
--- a/drivers/i2c/busses/i2c-ibm_iic.c 2004-07-14 17:00:40 -07:00
+++ b/drivers/i2c/busses/i2c-ibm_iic.c 2004-07-14 17:00:40 -07:00
@@ -45,7 +45,7 @@

#include "i2c-ibm_iic.h"

-#define DRIVER_VERSION "2.01"
+#define DRIVER_VERSION "2.1"

MODULE_DESCRIPTION("IBM IIC driver v" DRIVER_VERSION);
MODULE_LICENSE("GPL");
@@ -96,6 +96,31 @@
# define DUMP_REGS(h,dev) ((void)0)
#endif

+/* Bus timings (in ns) for bit-banging */
+static struct i2c_timings {
+ unsigned int hd_sta;
+ unsigned int su_sto;
+ unsigned int low;
+ unsigned int high;
+ unsigned int buf;
+} timings [] = {
+/* Standard mode (100 KHz) */
+{
+ .hd_sta = 4000,
+ .su_sto = 4000,
+ .low = 4700,
+ .high = 4000,
+ .buf = 4700,
+},
+/* Fast mode (400 KHz) */
+{
+ .hd_sta = 600,
+ .su_sto = 600,
+ .low = 1300,
+ .high = 600,
+ .buf = 1300,
+}};
+
/* Enable/disable interrupt generation */
static inline void iic_interrupt_mode(struct ibm_iic_private* dev, int enable)
{
@@ -196,6 +221,104 @@
}

/*
+ * Do 0-length transaction using bit-banging through IIC_DIRECTCNTL register.
+ */
+
+/* Wait for SCL and/or SDA to be high */
+static int iic_dc_wait(volatile struct iic_regs *iic, u8 mask)
+{
+ unsigned long x = jiffies + HZ / 28 + 2;
+ while ((in_8(&iic->directcntl) & mask) != mask){
+ if (unlikely(time_after(jiffies, x)))
+ return -1;
+ cond_resched();
+ }
+ return 0;
+}
+
+static int iic_smbus_quick(struct ibm_iic_private* dev, const struct i2c_msg* p)
+{
+ volatile struct iic_regs* iic = dev->vaddr;
+ const struct i2c_timings* t = &timings[dev->fast_mode ? 1 : 0];
+ u8 mask, v, sda;
+ int i, res;
+
+ /* Only 7-bit addresses are supported */
+ if (unlikely(p->flags & I2C_M_TEN)){
+ DBG("%d: smbus_quick - 10 bit addresses are not supported\n",
+ dev->idx);
+ return -EINVAL;
+ }
+
+ DBG("%d: smbus_quick(0x%02x)\n", dev->idx, p->addr);
+
+ /* Reset IIC interface */
+ out_8(&iic->xtcntlss, XTCNTLSS_SRST);
+
+ /* Wait for bus to become free */
+ out_8(&iic->directcntl, DIRCNTL_SDAC | DIRCNTL_SCC);
+ if (unlikely(iic_dc_wait(iic, DIRCNTL_MSDA | DIRCNTL_MSC)))
+ goto err;
+ ndelay(t->buf);
+
+ /* START */
+ out_8(&iic->directcntl, DIRCNTL_SCC);
+ sda = 0;
+ ndelay(t->hd_sta);
+
+ /* Send address */
+ v = (u8)((p->addr << 1) | ((p->flags & I2C_M_RD) ? 1 : 0));
+ for (i = 0, mask = 0x80; i < 8; ++i, mask >>= 1){
+ out_8(&iic->directcntl, sda);
+ ndelay(t->low / 2);
+ sda = (v & mask) ? DIRCNTL_SDAC : 0;
+ out_8(&iic->directcntl, sda);
+ ndelay(t->low / 2);
+
+ out_8(&iic->directcntl, DIRCNTL_SCC | sda);
+ if (unlikely(iic_dc_wait(iic, DIRCNTL_MSC)))
+ goto err;
+ ndelay(t->high);
+ }
+
+ /* ACK */
+ out_8(&iic->directcntl, sda);
+ ndelay(t->low / 2);
+ out_8(&iic->directcntl, DIRCNTL_SDAC);
+ ndelay(t->low / 2);
+ out_8(&iic->directcntl, DIRCNTL_SDAC | DIRCNTL_SCC);
+ if (unlikely(iic_dc_wait(iic, DIRCNTL_MSC)))
+ goto err;
+ res = (in_8(&iic->directcntl) & DIRCNTL_MSDA) ? -EREMOTEIO : 1;
+ ndelay(t->high);
+
+ /* STOP */
+ out_8(&iic->directcntl, 0);
+ ndelay(t->low);
+ out_8(&iic->directcntl, DIRCNTL_SCC);
+ if (unlikely(iic_dc_wait(iic, DIRCNTL_MSC)))
+ goto err;
+ ndelay(t->su_sto);
+ out_8(&iic->directcntl, DIRCNTL_SDAC | DIRCNTL_SCC);
+
+ ndelay(t->buf);
+
+ DBG("%d: smbus_quick -> %s\n", dev->idx, res ? "NACK" : "ACK");
+out:
+ /* Remove reset */
+ out_8(&iic->xtcntlss, 0);
+
+ /* Reinitialize interface */
+ iic_dev_init(dev);
+
+ return res;
+err:
+ DBG("%d: smbus_quick - bus is stuck\n", dev->idx);
+ res = -EREMOTEIO;
+ goto out;
+}
+
+/*
* IIC interrupt handler
*/
static irqreturn_t iic_handler(int irq, void *dev_id, struct pt_regs *regs)
@@ -457,13 +580,10 @@
if (unlikely(msgs[i].len <= 0)){
if (num == 1 && !msgs[0].len){
/* Special case for I2C_SMBUS_QUICK emulation.
- * Although this logic is FAR FROM PERFECT, this
- * is what previous driver version did.
* IBM IIC doesn't support 0-length transactions
- * (except bit-banging through IICx_DIRECTCNTL).
+ * so we have to emulate them using bit-banging.
*/
- DBG("%d: zero-length msg kludge\n", dev->idx);
- return 0;
+ return iic_smbus_quick(dev, &msgs[0]);
}
DBG("%d: invalid len %d in msg[%d]\n", dev->idx,
msgs[i].len, i);