Optimize the i2c_dw_read() function by reading the message flags only
once per message, rather than for every byte.

The message flags are accessed both in the outer loop and the inner loop,
so move the declaration of the local flags variable to the outer loop.

The message index is only modified by the outer loop, so reading the
flags in the inner loop was always getting the same value.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>
---
 drivers/i2c/busses/i2c-designware-master.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
index 45bfca05bb30..4493568e2fa3 100644
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -593,11 +593,12 @@ i2c_dw_read(struct dw_i2c_dev *dev)
 	unsigned int rx_valid;
 
 	for (; dev->msg_read_idx < dev->msgs_num; dev->msg_read_idx++) {
+		u32 flags = msgs[dev->msg_read_idx].flags;
 		unsigned int tmp;
 		u32 len;
 		u8 *buf;
 
-		if (!(msgs[dev->msg_read_idx].flags & I2C_M_RD))
+		if (!(flags & I2C_M_RD))
 			continue;
 
 		if (!(dev->status & STATUS_READ_IN_PROGRESS)) {
@@ -611,8 +612,6 @@ i2c_dw_read(struct dw_i2c_dev *dev)
 		regmap_read(dev->map, DW_IC_RXFLR, &rx_valid);
 
 		for (; len > 0 && rx_valid > 0; len--, rx_valid--) {
-			u32 flags = msgs[dev->msg_read_idx].flags;
-
 			regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
 			tmp &= DW_IC_DATA_CMD_DAT;
 			/* Ensure length byte is a valid value */

-- 
2.52.0

Hi Benoit,

On Tue, Jan 20, 2026 at 10:28:01AM +0100, Benoît Monin wrote:
> Optimize the i2c_dw_read() function by reading the message flags only
> once per message, rather than for every byte.
> 
> The message flags are accessed both in the outer loop and the inner loop,
> so move the declaration of the local flags variable to the outer loop.
> 
> The message index is only modified by the outer loop, so reading the
> flags in the inner loop was always getting the same value.
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>

This patch has already been applied. If you are going to respin,
please take it off.

Andi