Staging: heci: fix setting h_is bit in h_csr register

Host software could issue interrupts to ME firmware, using H_IG bit. While
Setting H_IG bit, host software should preserve all the other bits in H_CSR
unchanged. In the original function which sets H_CSR register, they first read
the register, then set some bits, and write the whole 32bits back to the
register. And that the special behavior of H_IS (write-one-to-zero) causes problem.
This patch fixes the issue in the following ways:

 - Modify heci_set_csr_register() function so that it doesn't change H_IS bit.
 - Add interface heci_csr_clear_his() to clear H_IS bit. This function is called
   after H_IS checking (dev->host_hw_state & H_IS == H_IS).
 - In original heci_csr_disable_interrupts() function, it not only clears H_IE
   bit, sometimes it also clears H_IS bit. This patch separates the two parts.
 - Avoid calling write_heci_register() function to set H_CSR register directly,
   and instead using heci_set_csr_register() function

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/heci/heci_init.c

@@ -249,7 +249,7 @@ int heci_hw_init(struct iamt_heci_device *dev)
 
 	if ((dev->host_hw_state & H_IS) == H_IS) {
 		/* acknowledge interrupt and stop interupts */
-		heci_set_csr_register(dev);
+		heci_csr_clear_his(dev);
 	}
 	dev->recvd_msg = 0;
 	DBG("reset in start the heci device.\n");
@@ -354,7 +354,7 @@ void heci_reset(struct iamt_heci_device *dev, int interrupts)
 	dev->host_hw_state &= ~H_RST;
 	dev->host_hw_state |= H_IG;
 
-	write_heci_register(dev, H_CSR, dev->host_hw_state);
+	heci_set_csr_register(dev);
 
 	DBG("currently saved host_hw_state = 0x%08x.\n",
 	    dev->host_hw_state);

drivers/staging/heci/heci_interface.c

@@ -44,12 +44,15 @@
 
 
 /**
- * heci_set_csr_register - write H_CSR register to the heci device
+ * heci_set_csr_register - write H_CSR register to the heci device,
+ * and ignore the H_IS bit for it is write-one-to-zero.
  *
  * @dev: device object for our driver
  */
 void heci_set_csr_register(struct iamt_heci_device *dev)
 {
+	if ((dev->host_hw_state & H_IS) == H_IS)
+		dev->host_hw_state &= ~H_IS;
 	write_heci_register(dev, H_CSR, dev->host_hw_state);
 	dev->host_hw_state = read_heci_register(dev, H_CSR);
 }
@@ -76,6 +79,16 @@ void heci_csr_disable_interrupts(struct iamt_heci_device *dev)
 	heci_set_csr_register(dev);
 }
 
+/**
+ * heci_csr_clear_his - clear H_IS bit in H_CSR
+ *
+ * @dev: device object for our driver
+ */
+void heci_csr_clear_his(struct iamt_heci_device *dev)
+{
+	write_heci_register(dev, H_CSR, dev->host_hw_state);
+	dev->host_hw_state = read_heci_register(dev, H_CSR);
+}
 
 /**
  * _host_get_filled_slots - get number of device filled buffer slots
@@ -185,7 +198,7 @@ int heci_write_message(struct iamt_heci_device *dev,
 	}
 
 	dev->host_hw_state |= H_IG;
-	write_heci_register(dev, H_CSR, dev->host_hw_state);
+	heci_set_csr_register(dev);
 	dev->me_hw_state = read_heci_register(dev, ME_CSR_HA);
 	if ((dev->me_hw_state & ME_RDY_HRA) != ME_RDY_HRA)
 		return 0;

drivers/staging/heci/heci_interface.h

@@ -133,6 +133,7 @@ enum client_disconnect_status_types{
 void heci_set_csr_register(struct iamt_heci_device *dev);
 void heci_csr_enable_interrupts(struct iamt_heci_device *dev);
 void heci_csr_disable_interrupts(struct iamt_heci_device *dev);
+void heci_csr_clear_his(struct iamt_heci_device *dev);
 
 void heci_read_slots(struct iamt_heci_device *dev,
 		     unsigned char *buffer, unsigned long buffer_length);

drivers/staging/heci/interrupt.c

@@ -92,6 +92,9 @@ irqreturn_t heci_isr_interrupt(int irq, void *dev_id)
 	/* disable interrupts */
 	heci_csr_disable_interrupts(dev);
 
+	/* clear H_IS bit in H_CSR */
+	heci_csr_clear_his(dev);
+
 	/*
 	 * Our device interrupted, schedule work the heci_bh_handler
 	 * to handle the interrupt processing. This needs to be a
@@ -251,6 +254,9 @@ end:
 		/* acknowledge interrupt and disable interrupts */
 		heci_csr_disable_interrupts(dev);
 
+		/* clear H_IS bit in H_CSR */
+		heci_csr_clear_his(dev);
+
 		PREPARE_WORK(&dev->work, heci_bh_handler);
 		DBG("schedule work the heci_bh_handler.\n");
 		rets = schedule_work(&dev->work);