hw/i2c/aspeed: Fix TXBUF transmission start position error

According to the ast2600 datasheet and the linux aspeed i2c driver,
the TXBUF transmission start position should be TXBUF[0] instead
of TXBUF[1],so the arg pool_start is useless,and the address is not
included in TXBUF.So even if Tx Count equals zero,there is at least
1 byte data needs to be transmitted,and M_TX_CMD should not be cleared
at this condition.The driver url is:
https://github.com/AspeedTech-BMC/linux/blob/aspeed-master-v5.15/drivers/i2c/busses/i2c-ast2600.c

Signed-off-by: Hang Yu <francis_yuu@stu.pku.edu.cn>
Fixes: 6054fc7 ("aspeed/i2c: Add support for pool buffer transfers")
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
(cherry picked from commit 961faf3)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/i2c/aspeed_i2c.c

@@ -226,7 +226,7 @@ static int aspeed_i2c_dma_read(AspeedI2CBus *bus, uint8_t *data)
     return 0;
 }
 
-static int aspeed_i2c_bus_send(AspeedI2CBus *bus, uint8_t pool_start)
+static int aspeed_i2c_bus_send(AspeedI2CBus *bus)
 {
     AspeedI2CClass *aic = ASPEED_I2C_GET_CLASS(bus->controller);
     int ret = -1;
@@ -239,7 +239,7 @@ static int aspeed_i2c_bus_send(AspeedI2CBus *bus, uint8_t pool_start)
                                                 TX_COUNT) + 1;
 
     if (SHARED_ARRAY_FIELD_EX32(bus->regs, reg_cmd, TX_BUFF_EN)) {
-        for (i = pool_start; i < pool_tx_count; i++) {
+        for (i = 0; i < pool_tx_count; i++) {
             uint8_t *pool_base = aic->bus_pool_base(bus);
 
             trace_aspeed_i2c_bus_send("BUF", i + 1, pool_tx_count,
@@ -273,7 +273,7 @@ static int aspeed_i2c_bus_send(AspeedI2CBus *bus, uint8_t pool_start)
         }
         SHARED_ARRAY_FIELD_DP32(bus->regs, reg_cmd, TX_DMA_EN, 0);
     } else {
-        trace_aspeed_i2c_bus_send("BYTE", pool_start, 1,
+        trace_aspeed_i2c_bus_send("BYTE", 0, 1,
                                   bus->regs[reg_byte_buf]);
         ret = i2c_send(bus->bus, bus->regs[reg_byte_buf]);
     }
@@ -446,10 +446,8 @@ static void aspeed_i2c_bus_cmd_dump(AspeedI2CBus *bus)
  */
 static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
 {
-    uint8_t pool_start = 0;
     uint32_t reg_intr_sts = aspeed_i2c_bus_intr_sts_offset(bus);
     uint32_t reg_cmd = aspeed_i2c_bus_cmd_offset(bus);
-    uint32_t reg_pool_ctrl = aspeed_i2c_bus_pool_ctrl_offset(bus);
     uint32_t reg_dma_len = aspeed_i2c_bus_dma_len_offset(bus);
 
     if (!aspeed_i2c_check_sram(bus)) {
@@ -483,27 +481,11 @@ static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
 
         SHARED_ARRAY_FIELD_DP32(bus->regs, reg_cmd, M_START_CMD, 0);
 
-        /*
-         * The START command is also a TX command, as the slave
-         * address is sent on the bus. Drop the TX flag if nothing
-         * else needs to be sent in this sequence.
-         */
-        if (SHARED_ARRAY_FIELD_EX32(bus->regs, reg_cmd, TX_BUFF_EN)) {
-            if (SHARED_ARRAY_FIELD_EX32(bus->regs, reg_pool_ctrl, TX_COUNT)
-                == 0) {
-                SHARED_ARRAY_FIELD_DP32(bus->regs, reg_cmd, M_TX_CMD, 0);
-            } else {
-                /*
-                 * Increase the start index in the TX pool buffer to
-                 * skip the address byte.
-                 */
-                pool_start++;
-            }
-        } else if (SHARED_ARRAY_FIELD_EX32(bus->regs, reg_cmd, TX_DMA_EN)) {
+        if (SHARED_ARRAY_FIELD_EX32(bus->regs, reg_cmd, TX_DMA_EN)) {
             if (bus->regs[reg_dma_len] == 0) {
                 SHARED_ARRAY_FIELD_DP32(bus->regs, reg_cmd, M_TX_CMD, 0);
             }
-        } else {
+        } else if (!SHARED_ARRAY_FIELD_EX32(bus->regs, reg_cmd, TX_BUFF_EN)) {
             SHARED_ARRAY_FIELD_DP32(bus->regs, reg_cmd, M_TX_CMD, 0);
         }
 
@@ -520,7 +502,7 @@ static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
 
     if (SHARED_ARRAY_FIELD_EX32(bus->regs, reg_cmd, M_TX_CMD)) {
         aspeed_i2c_set_state(bus, I2CD_MTXD);
-        if (aspeed_i2c_bus_send(bus, pool_start)) {
+        if (aspeed_i2c_bus_send(bus)) {
             SHARED_ARRAY_FIELD_DP32(bus->regs, reg_intr_sts, TX_NAK, 1);
             i2c_end_transfer(bus->bus);
         } else {