i2c: i2c-cdns: Start read transaction after write to transfer_size reg

Avoid a race condition where read transaction is started
keeping expected bytes as 0. Which sometimes would result in sending
STOP signal as no data is expected. Observed on QEMU platform.

Signed-off-by: Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>
Reviewed-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/487c8026791bfd60719403a2df2c54bb0ae99232.1646122610.git.michal.simek@xilinx.com

diff --git a/drivers/i2c/i2c-cdns.c b/drivers/i2c/i2c-cdns.c
index a650dd6..5736afb 100644 (file)
--- a/drivers/i2c/i2c-cdns.c
+++ b/drivers/i2c/i2c-cdns.c
@@ -375,7 +375,6 @@ static int cdns_i2c_read_data(struct i2c_cdns_bus *i2c_bus, u32 addr, u8 *data,
                                curr_recv_count = recv_count;
                        }
                } else if (recv_count && !hold_quirk && !curr_recv_count) {
-                       writel(addr, &regs->address);
                        if (recv_count > CDNS_I2C_TRANSFER_SIZE) {
                                writel(CDNS_I2C_TRANSFER_SIZE,
                                       &regs->transfer_size);
@@ -384,6 +383,7 @@ static int cdns_i2c_read_data(struct i2c_cdns_bus *i2c_bus, u32 addr, u8 *data,
                                writel(recv_count, &regs->transfer_size);
                                curr_recv_count = recv_count;
                        }
+                       writel(addr, &regs->address);
                }
        }