aspeed/i2c: interrupts should be cleared by software only

aspeed i2c interrupts should be cleared by software only, and the bus
interrupt should be lowered when all interrupts have been cleared.
Signed-off-by: NCédric Le Goater <clg@kaod.org>
Message-id: 20180914063506.20815-2-clg@kaod.org
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
[PMM: drop TODO comment describing an issue which is
 fixed later in the patch series, and clean up commit message]
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/i2c/aspeed_i2c.c

@@ -52,6 +52,13 @@
 #define I2CD_AC_TIMING_REG2     0x08       /* Clock and AC Timing Control #1 */
 #define I2CD_INTR_CTRL_REG      0x0c       /* I2CD Interrupt Control */
 #define I2CD_INTR_STS_REG       0x10       /* I2CD Interrupt Status */
+
+#define   I2CD_INTR_SLAVE_ADDR_MATCH       (0x1 << 31) /* 0: addr1 1: addr2 */
+#define   I2CD_INTR_SLAVE_ADDR_RX_PENDING  (0x1 << 30)
+/* bits[19-16] Reserved */
+
+/* All bits below are cleared by writing 1 */
+#define   I2CD_INTR_SLAVE_INACTIVE_TIMEOUT (0x1 << 15)
 #define   I2CD_INTR_SDA_DL_TIMEOUT         (0x1 << 14)
 #define   I2CD_INTR_BUS_RECOVER_DONE       (0x1 << 13)
 #define   I2CD_INTR_SMBUS_ALERT            (0x1 << 12) /* Bus [0-3] only */
@@ -59,7 +66,7 @@
 #define   I2CD_INTR_SMBUS_DEV_ALERT_ADDR   (0x1 << 10) /* Removed */
 #define   I2CD_INTR_SMBUS_DEF_ADDR         (0x1 << 9)  /* Removed */
 #define   I2CD_INTR_GCALL_ADDR             (0x1 << 8)  /* Removed */
-#define   I2CD_INTR_SLAVE_MATCH            (0x1 << 7)  /* use RX_DONE */
+#define   I2CD_INTR_SLAVE_ADDR_RX_MATCH    (0x1 << 7)  /* use RX_DONE */
 #define   I2CD_INTR_SCL_TIMEOUT            (0x1 << 6)
 #define   I2CD_INTR_ABNORMAL               (0x1 << 5)
 #define   I2CD_INTR_NORMAL_STOP            (0x1 << 4)
@@ -188,7 +195,6 @@ static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
 {
     bus->cmd &= ~0xFFFF;
     bus->cmd |= value & 0xFFFF;
-    bus->intr_status = 0;
 
     if (bus->cmd & I2CD_M_START_CMD) {
         uint8_t state = aspeed_i2c_get_state(bus) & I2CD_MACTIVE ?
@@ -284,8 +290,10 @@ static void aspeed_i2c_bus_write(void *opaque, hwaddr offset,
         break;
     case I2CD_INTR_STS_REG:
         bus->intr_status &= ~(value & 0x7FFF);
-        bus->controller->intr_status &= ~(1 << bus->id);
-        qemu_irq_lower(bus->controller->irq);
+        if (!bus->intr_status) {
+            bus->controller->intr_status &= ~(1 << bus->id);
+            qemu_irq_lower(bus->controller->irq);
+        }
         break;
     case I2CD_DEV_ADDR_REG:
         qemu_log_mask(LOG_UNIMP, "%s: slave mode not implemented\n",