Re: [PATCH v2 1/3] hwmon: (pmbus/tps53679) Fix TPS53676 phase page decoding

[Guenter Roeck]

Hi,

On 9/15/26 09:48, Pradhan, Sanman wrote:
> From: Sanman Pradhan <psanman@xxxxxxxxxxx>
>
> tps53676_identify() reads the USER_DATA_03 phase configuration to count
> the phases assigned to each channel and derive the number of PMBus pages.
> In each 16-bit phase descriptor the channel (PAGE) is encoded in bit 4 and
> the firing order in bits 3:0, but the code tested bit 3 (0x08), which is
> part of the firing-order field.
>
> TPS53676 supports up to seven phases, so firing-order bit 3 is never set.
> As a result the existing test classifies every enabled phase as channel A.
> On a dual-channel configuration the phases assigned to channel B are
> therefore miscounted as channel A and page 1 is not exposed.
>
> Test the PAGE field (bit 4) instead.

tps53676_identify() has a second problem: It does not set the current page
to 0 for single-page systems. If the BIOS/ROMMON had selected page 1 for
some reason, the page register is never updated because pmbus_set_page()
does not set the page number if the number of pages is 1. Please fix that
as well.

Thanks,
Guenter

> Fixes: cb3d37b59012 ("hwmon: (pmbus/tps53679) Add support for TI TPS53676")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Sanman Pradhan <psanman@xxxxxxxxxxx>
> ---
>   drivers/hwmon/pmbus/tps53679.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/pmbus/tps53679.c b/drivers/hwmon/pmbus/tps53679.c
> index fa0fdf1e3e6c9..680339a6b90fe 100644
> --- a/drivers/hwmon/pmbus/tps53679.c
> +++ b/drivers/hwmon/pmbus/tps53679.c
> @@ -188,7 +188,7 @@ static int tps53676_identify(struct i2c_client *client,
>   		return -EIO;
>   	for (i = 0; i < 2 * TPS53676_MAX_PHASES; i += 2) {
>   		if (buf[i + 1] & 0x80) {
> -			if (buf[i] & 0x08)
> +			if (buf[i] & BIT(4))
>   				phases_b++;
>   			else
>   				phases_a++;