Re: [U-Boot] [PATCH] Exynos5: i2c: Fix read NACK handling and remove some redundancy

Hi Hung-ying Tyan,

On which branch is this patch based? It looks quite off from ToT.

I rebased this patch on u-boot-samsung and posted. But it's been quite some time since I posted it, so I am not sure if it could be applied straightway now.

On Mon, Mar 25, 2013 at 7:46 PM, Akshay Saraswat akshay.s@samsung.com wrote:

From: Gabe Black gabeblack@google.com

The exynos s3c24x0 i2c driver wouldn't do the right thing when a NACK was received on a read because it didn't attempt a read before waiting for the read to finish. Putting a call to ReadWriteByte in the NACK path fixed a problem where getting a NACK reading from a device would jam up the bus and prevent future accesses like probing from working.

Because other than the ReadWriteByte call the NACK and normal paths were almost the same thing, and to avoid future instances of the NACK path not working because it's not exercised normally, this change also consolidates those two paths.

Signed-off-by: Gabe Black gabeblack@google.com Signed-off-by: Akshay Saraswat akshay.s@samsung.com

---

drivers/i2c/s3c24x0_i2c.c | 53 ++++++++++++++++------------------------------- 1 file changed, 18 insertions(+), 35 deletions(-)

diff --git a/drivers/i2c/s3c24x0_i2c.c b/drivers/i2c/s3c24x0_i2c.c index d2b4eb0..91298a7 100644 --- a/drivers/i2c/s3c24x0_i2c.c +++ b/drivers/i2c/s3c24x0_i2c.c @@ -366,21 +366,25 @@ static int i2c_transfer(struct s3c24x0_i2c *i2c, break;

   case I2C_READ:

•           if (result == I2C_OK) {
  

•                   writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
  

•                   writel(chip, &i2c->iicds);
  

•                   /* send START */
  

•                   writel(readl(&i2c->iicstat) | I2C_START_STOP,
  

•                          &i2c->iicstat);
  

•                   ReadWriteByte(i2c);
  

•                   result = WaitForXfer(i2c);
  

•   {
  

•           int was_ok = (result == I2C_OK);
  

•           writel(chip, &i2c->iicds);
  

•           /* resend START */
  

•           writel(I2C_MODE_MR | I2C_TXRX_ENA |
  

•                                   I2C_START_STOP, &i2c->iicstat);
  

•           ReadWriteByte(i2c);
  

•           result = WaitForXfer(i2c);
  

•           if (was_ok || IsACK(i2c)) {
                   i = 0;
                   while ((i < data_len) && (result == I2C_OK)) {
                           /* disable ACK for final READ */
  

•                           if (i == data_len - 1)
  

•                                   writel(readl(&i2c->iiccon)
  

•                                                   & ~I2CCON_ACKGEN,
  

•                                                   &i2c->iiccon);
  

•                           if (i == data_len - 1) {
  

•                                   writel(readl(&i2c->iiccon) &
  

•                                         ~I2CCON_ACKGEN,
  

•                                         &i2c->iiccon);
  

•                           }
                           ReadWriteByte(i2c);
                           result = WaitForXfer(i2c);
                           data[i] = readl(&i2c->iicds);
  

@@ -388,35 +392,14 @@ static int i2c_transfer(struct s3c24x0_i2c *i2c, }

           } else {

•                   writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
  

•                   writel(chip, &i2c->iicds);
  

•                   /* send START */
  

•                   writel(readl(&i2c->iicstat) | I2C_START_STOP,
  

•                          &i2c->iicstat);
  

•                   result = WaitForXfer(i2c);
  

•                   if (IsACK(i2c)) {
  

•                           i = 0;
  

•                           while ((i < data_len) && (result == I2C_OK)) {
  

•                                   /* disable ACK for final READ */
  

•                                   if (i == data_len - 1)
  

•                                           writel(readl(&i2c->iiccon) &
  

•                                                   ~I2CCON_ACKGEN,
  

•                                                   &i2c->iiccon);
  

•                                   ReadWriteByte(i2c);
  

•                                   result = WaitForXfer(i2c);
  

•                                   data[i] = readl(&i2c->iicds);
  

•                                   i++;
  

•                           }
  

•                   } else {
  

•                           result = I2C_NACK;
  

•                   }
  

•                   result = I2C_NACK;
           }
  
           /* send STOP */
           writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
           ReadWriteByte(i2c);
           break;
  

•   }
  
   default:
           debug("i2c_transfer: bad call\n");
  

-- 1.8.0

Regards, Akshay Saraswat