[PATCH 1/1] hw/i2c/aspeed: Fix old reg slave receive

[Peter Delevoryas <peter@pjd.dev>]

I think when Klaus ported his slave mode changes from the original patch
series to the rewritten I2C module, he changed the behavior of the first
byte that is received by the slave device.

What's supposed to happen is that the AspeedI2CBus's slave device's
i2c_event callback should run, and if the event is "send_async", then it
should populate the byte buffer with the 8-bit I2C address that is being
sent to. Since we only support "send_async", the lowest bit should
always be 0 (indicating that the master is requesting to send data).

This is the code Klaus had previously, for reference. [1]

    switch (event) {
    case I2C_START_SEND:
        bus->buf = bus->dev_addr << 1;

        bus->buf &= I2CD_BYTE_BUF_RX_MASK;
        bus->buf <<= I2CD_BYTE_BUF_RX_SHIFT;

        bus->intr_status |= (I2CD_INTR_SLAVE_ADDR_RX_MATCH | I2CD_INTR_RX_DONE);
        aspeed_i2c_set_state(bus, I2CD_STXD);

        break;

[1]: https://lore.kernel.org/qemu-devel/20220331165737.1073520-4-its@irrelevant.dk/

Signed-off-by: Peter Delevoryas <peter@pjd.dev>
Fixes: a8d48f59cd021b25 ("hw/i2c/aspeed: add slave device in old register mode")
---
 hw/i2c/aspeed_i2c.c         | 8 +++++---
 include/hw/i2c/aspeed_i2c.h | 1 +
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/hw/i2c/aspeed_i2c.c b/hw/i2c/aspeed_i2c.c
index 42c6d69b82..c166fd20fa 100644
--- a/hw/i2c/aspeed_i2c.c
+++ b/hw/i2c/aspeed_i2c.c
@@ -1131,7 +1131,9 @@ static int aspeed_i2c_bus_slave_event(I2CSlave *slave, enum i2c_event event)
     AspeedI2CBus *bus = ASPEED_I2C_BUS(qbus->parent);
     uint32_t reg_intr_sts = aspeed_i2c_bus_intr_sts_offset(bus);
     uint32_t reg_byte_buf = aspeed_i2c_bus_byte_buf_offset(bus);
-    uint32_t value;
+    uint32_t reg_dev_addr = aspeed_i2c_bus_dev_addr_offset(bus);
+    uint32_t dev_addr = SHARED_ARRAY_FIELD_EX32(bus->regs, reg_dev_addr,
+                                                SLAVE_DEV_ADDR1);
 
     if (aspeed_i2c_is_new_mode(bus->controller)) {
         return aspeed_i2c_bus_new_slave_event(bus, event);
@@ -1139,8 +1141,8 @@ static int aspeed_i2c_bus_slave_event(I2CSlave *slave, enum i2c_event event)
 
     switch (event) {
     case I2C_START_SEND_ASYNC:
-        value = SHARED_ARRAY_FIELD_EX32(bus->regs, reg_byte_buf, TX_BUF);
-        SHARED_ARRAY_FIELD_DP32(bus->regs, reg_byte_buf, RX_BUF, value << 1);
+        /* Bit[0] == 0 indicates "send". */
+        SHARED_ARRAY_FIELD_DP32(bus->regs, reg_byte_buf, RX_BUF, dev_addr << 1);
 
         ARRAY_FIELD_DP32(bus->regs, I2CD_INTR_STS, SLAVE_ADDR_RX_MATCH, 1);
         SHARED_ARRAY_FIELD_DP32(bus->regs, reg_intr_sts, RX_DONE, 1);
diff --git a/include/hw/i2c/aspeed_i2c.h b/include/hw/i2c/aspeed_i2c.h
index 300a89b343..adc904d6c1 100644
--- a/include/hw/i2c/aspeed_i2c.h
+++ b/include/hw/i2c/aspeed_i2c.h
@@ -130,6 +130,7 @@ REG32(I2CD_CMD, 0x14) /* I2CD Command/Status */
     SHARED_FIELD(M_TX_CMD, 1, 1)
     SHARED_FIELD(M_START_CMD, 0, 1)
 REG32(I2CD_DEV_ADDR, 0x18) /* Slave Device Address */
+    SHARED_FIELD(SLAVE_DEV_ADDR1, 0, 7)
 REG32(I2CD_POOL_CTRL, 0x1C) /* Pool Buffer Control */
     SHARED_FIELD(RX_COUNT, 24, 5)
     SHARED_FIELD(RX_SIZE, 16, 5)
-- 
2.37.1