On Wed, Sep 12, 2018 at 03:31:06PM -0700, Jae Hyun Yoo wrote:

quoted

I played with the code on both sides. I had to make changes in both
the linux kernel and in qemu to get the code to work again.
See attached.

Guenter

---
Linux:

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index c258c4d9a4c0..3d518e09369f 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c

@@ -552,6 +552,9 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
 	spin_lock(&bus->lock);
 	irq_received = readl(bus->base + ASPEED_I2C_INTR_STS_REG);
+	/* Ack all interrupts except for Rx done */
+	writel(irq_received & ~ASPEED_I2CD_INTR_RX_DONE,
+	       bus->base + ASPEED_I2C_INTR_STS_REG);
 	irq_remaining = irq_received;
 #if IS_ENABLED(CONFIG_I2C_SLAVE)

@@ -584,8 +587,10 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
 			"irq handled != irq. expected 0x%08x, but was 0x%08x\n",
 			irq_received, irq_handled);
-	/* Ack all interrupt bits. */
-	writel(irq_received, bus->base + ASPEED_I2C_INTR_STS_REG);
+	/* Ack Rx done */
+	if (irq_received & ASPEED_I2CD_INTR_RX_DONE)
+		writel(ASPEED_I2CD_INTR_RX_DONE,
+		       bus->base + ASPEED_I2C_INTR_STS_REG);
 	spin_unlock(&bus->lock);
 	return irq_remaining ? IRQ_NONE : IRQ_HANDLED;
 }

---
qemu:

diff --git a/hw/i2c/aspeed_i2c.c b/hw/i2c/aspeed_i2c.c
index c762c73..0d4aa08 100644
--- a/hw/i2c/aspeed_i2c.c
+++ b/hw/i2c/aspeed_i2c.c

@@ -180,6 +180,33 @@ static uint8_t aspeed_i2c_get_state(AspeedI2CBus *bus)
     return (bus->cmd >> I2CD_TX_STATE_SHIFT) & I2CD_TX_STATE_MASK;
 }
+static void aspeed_i2c_handle_rx_cmd(AspeedI2CBus *bus)
+{
+    int ret;
+
+    if (!(bus->cmd & (I2CD_M_RX_CMD | I2CD_M_S_RX_CMD_LAST))) {
+        return;
+    }
+    if (bus->intr_status & I2CD_INTR_RX_DONE) {
+        return;
+    }
+
+    aspeed_i2c_set_state(bus, I2CD_MRXD);
+    ret = i2c_recv(bus->bus);
+    if (ret < 0) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: read failed\n", __func__);
+        ret = 0xff;
+    } else {
+        bus->intr_status |= I2CD_INTR_RX_DONE;
+    }
+    bus->buf = (ret & I2CD_BYTE_BUF_RX_MASK) << I2CD_BYTE_BUF_RX_SHIFT;
+    if (bus->cmd & I2CD_M_S_RX_CMD_LAST) {
+        i2c_nack(bus->bus);
+    }
+    bus->cmd &= ~(I2CD_M_RX_CMD | I2CD_M_S_RX_CMD_LAST);
+    aspeed_i2c_set_state(bus, I2CD_MACTIVE);
+}
+
 /*
  * The state machine needs some refinement. It is only used to track
  * invalid STOP commands for the moment.

@@ -188,7 +215,7 @@ static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
 {
     bus->cmd &= ~0xFFFF;
     bus->cmd |= value & 0xFFFF;
-    bus->intr_status = 0;
+    bus->intr_status &= I2CD_INTR_RX_DONE;
     if (bus->cmd & I2CD_M_START_CMD) {
         uint8_t state = aspeed_i2c_get_state(bus) & I2CD_MACTIVE ?

@@ -227,22 +254,7 @@ static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
     }
     if (bus->cmd & (I2CD_M_RX_CMD | I2CD_M_S_RX_CMD_LAST)) {
-        int ret;
-
-        aspeed_i2c_set_state(bus, I2CD_MRXD);
-        ret = i2c_recv(bus->bus);
-        if (ret < 0) {
-            qemu_log_mask(LOG_GUEST_ERROR, "%s: read failed\n", __func__);
-            ret = 0xff;
-        } else {
-            bus->intr_status |= I2CD_INTR_RX_DONE;
-        }
-        bus->buf = (ret & I2CD_BYTE_BUF_RX_MASK) << I2CD_BYTE_BUF_RX_SHIFT;
-        if (bus->cmd & I2CD_M_S_RX_CMD_LAST) {
-            i2c_nack(bus->bus);
-        }
-        bus->cmd &= ~(I2CD_M_RX_CMD | I2CD_M_S_RX_CMD_LAST);
-        aspeed_i2c_set_state(bus, I2CD_MACTIVE);
+        aspeed_i2c_handle_rx_cmd(bus);
     }
     if (bus->cmd & I2CD_M_STOP_CMD) {

@@ -263,6 +275,7 @@ static void aspeed_i2c_bus_write(void *opaque, hwaddr offset,
                                  uint64_t value, unsigned size)
 {
     AspeedI2CBus *bus = opaque;
+    int status;
     switch (offset) {
     case I2CD_FUN_CTRL_REG:

@@ -283,9 +296,16 @@ static void aspeed_i2c_bus_write(void *opaque, hwaddr offset,
         bus->intr_ctrl = value & 0x7FFF;
         break;
     case I2CD_INTR_STS_REG:
+        status = bus->intr_status;
         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);
+        }
+        if ((status & I2CD_INTR_RX_DONE) && !(bus->intr_status & I2CD_INTR_RX_DONE)) {
+            aspeed_i2c_handle_rx_cmd(bus);
+            aspeed_i2c_bus_raise_interrupt(bus);
+        }
         break;
     case I2CD_DEV_ADDR_REG:
         qemu_log_mask(LOG_UNIMP, "%s: slave mode not implemented\n",

Nice fix! LGTM. I've tested the new patch and checked that it works well
on both low and high bus speed environments. Thanks a lot!

Can you please submit this patch?

Assuming you mean both patches, sure, can do. I'll need to clean up
the qemu patch a bit, though; it looks too messy for my liking.

Guenter