[PATCH net] net: dsa: mv88e6xxx: Wait for EEPROM done before HW reset

[PATCH net] net: dsa: mv88e6xxx: Wait for EEPROM done before HW reset

[Alfred Lee]

If the switch is reset during active EEPROM transactions, as in
just after an SoC reset after power up, the I2C bus transaction
may be cut short leaving the EEPROM internal I2C state machine
in the wrong state.  When the switch is reset again, the bad
state machine state may result in data being read from the wrong
memory location causing the switch to enter unexpect mode
rendering it inoperational.

Signed-off-by: Alfred Lee <l00g33k@gmail.com>
Fixes: 8abbffd27ced ("net: dsa: mv88e6xxx: Wait for EEPROM done after HW reset")
---
 drivers/net/dsa/mv88e6xxx/chip.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index c7d51a539451..7af2f08a62f1 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -3034,6 +3034,14 @@ static void mv88e6xxx_hardware_reset(struct mv88e6xxx_chip *chip)
 
 	/* If there is a GPIO connected to the reset pin, toggle it */
 	if (gpiod) {
+		/* If the switch has just been reset and not yet completed
+		 * loading EEPROM, the reset may interrupt the I2C transaction
+		 * mid-byte, causing the first EEPROM read after the reset
+		 * from the wrong location resulting in the switch booting
+		 * to wrong mode and inoperable.
+		 */
+		mv88e6xxx_g1_wait_eeprom_done(chip);
+
 		gpiod_set_value_cansleep(gpiod, 1);
 		usleep_range(10000, 20000);
 		gpiod_set_value_cansleep(gpiod, 0);
-- 
2.41.0

Re: [PATCH net] net: dsa: mv88e6xxx: Wait for EEPROM done before HW reset

[Andrew Lunn]

On Fri, Aug 11, 2023 at 01:30:20PM -0700, Alfred Lee wrote:
> If the switch is reset during active EEPROM transactions, as in
> just after an SoC reset after power up, the I2C bus transaction
> may be cut short leaving the EEPROM internal I2C state machine
> in the wrong state. When the switch is reset again, the bad
> state machine state may result in data being read from the wrong
> memory location causing the switch to enter unexpect mode
> rendering it inoperational.
> 
> Fixes: 8abbffd27ced ("net: dsa: mv88e6xxx: Wait for EEPROM done after HW
> reset")
> Signed-off-by: Alfred Lee <l00g33k@gmail.com>
> ---
> drivers/net/dsa/mv88e6xxx/chip.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/
> chip.c
> index c7d51a539451..7af2f08a62f1 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.c
> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> @@ -3034,6 +3034,14 @@ static void mv88e6xxx_hardware_reset(struct
> mv88e6xxx_chip *chip)
> /* If there is a GPIO connected to the reset pin, toggle it */
> if (gpiod) {
> + /* If the switch has just been reset and not yet completed
> + * loading EEPROM, the reset may interrupt the I2C transaction
> + * mid-byte, causing the first EEPROM read after the reset
> + * from the wrong location resulting in the switch booting
> + * to wrong mode and inoperable.
> + */
> + mv88e6xxx_g1_wait_eeprom_done(chip);
> +
> gpiod_set_value_cansleep(gpiod, 1);
> usleep_range(10000, 20000);
> gpiod_set_value_cansleep(gpiod, 0);

Hi Alfred

It looks like all the white spacing in the email has been
destroyed. Please check your mail configuration. You might want to
email the patch to only yourself, and then make sure it cleanly
applies via 'git am'

    Andrew

---
pw-bot: cr