i2c: npcm: Enable slave in eob interrupt

Nuvoton slave enable was in user space API call master_xfer, so it is
subject to delays from the OS scheduler. If the BMC is not enabled for
slave mode in time for master to send response, then it will NAK the
address match. Then the PLDM request timeout occurs.

If the slave enable is moved to the EOB interrupt service routine, then
the BMC can be ready in slave mode by the time it needs to receive a
response.

Signed-off-by: Charles Boyer <Charles.Boyer@fii-usa.com>
Signed-off-by: Vivekanand Veeracholan <vveerach@google.com>
Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
Link: https://lore.kernel.org/r/20241219090859.18722-5-kfting@nuvoton.com
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 1aae1a8a8055866de7033aa298d5d43d48f64260..3ca08b8ef8af3cf5819329daecec3878aecb1358 100644 (file)
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -1925,6 +1925,12 @@ static int npcm_i2c_int_master_handler(struct npcm_i2c *bus)
            (FIELD_GET(NPCM_I2CCST3_EO_BUSY,
                       ioread8(bus->reg + NPCM_I2CCST3)))) {
                npcm_i2c_irq_handle_eob(bus);
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+               /* reenable slave if it was enabled */
+               if (bus->slave)
+                       iowrite8(bus->slave->addr | NPCM_I2CADDR_SAEN,
+                                bus->reg + NPCM_I2CADDR1);
+#endif
                return 0;
        }