ahci_xgene: fix the dma state machine lockup for the IDENTIFY DEVICE PIO mode command.

This patch fixes the dma state machine lockup due to the processing
of IDENTIFY DEVICE PIO mode command. The X-Gene AHCI controller
has an errata in which it cannot clear the BSY bit after the PIO setup
FIS. The dma state machine enters CMFatalErrorUpdate state and locks
up. This patch also removes the dma restart workaround from the read_id
function as the read_id function is only called by libata layer for
ATA_INTERNAL commands. But for some cases eg: PORT MULTIPLIER
and udev, the framework will enumerate using SCSI commands and it will
not call read_id function.
Signed-off-by: Loc Ho <lho@apm.com>
Signed-off-by: Suman Tripathi <stripathi@apm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/ahci_xgene.c

@@ -78,6 +78,7 @@
 struct xgene_ahci_context {
 	struct ahci_host_priv *hpriv;
 	struct device *dev;
+	u8 last_cmd[MAX_AHCI_CHN_PERCTR]; /* tracking the last command issued*/
 	void __iomem *csr_core;		/* Core CSR address of IP */
 	void __iomem *csr_diag;		/* Diag CSR address of IP */
 	void __iomem *csr_axi;		/* AXI CSR address of IP */
@@ -97,6 +98,50 @@ static int xgene_ahci_init_memram(struct xgene_ahci_context *ctx)
 	return 0;
 }
 
+/**
+ * xgene_ahci_restart_engine - Restart the dma engine.
+ * @ap : ATA port of interest
+ *
+ * Restarts the dma engine inside the controller.
+ */
+static int xgene_ahci_restart_engine(struct ata_port *ap)
+{
+	struct ahci_host_priv *hpriv = ap->host->private_data;
+
+	ahci_stop_engine(ap);
+	ahci_start_fis_rx(ap);
+	hpriv->start_engine(ap);
+
+	return 0;
+}
+
+/**
+ * xgene_ahci_qc_issue - Issue commands to the device
+ * @qc: Command to issue
+ *
+ * Due to Hardware errata for IDENTIFY DEVICE command, the controller cannot
+ * clear the BSY bit after receiving the PIO setup FIS. This results in the dma
+ * state machine goes into the CMFatalErrorUpdate state and locks up. By
+ * restarting the dma engine, it removes the controller out of lock up state.
+ */
+static unsigned int xgene_ahci_qc_issue(struct ata_queued_cmd *qc)
+{
+	struct ata_port *ap = qc->ap;
+	struct ahci_host_priv *hpriv = ap->host->private_data;
+	struct xgene_ahci_context *ctx = hpriv->plat_data;
+	int rc = 0;
+
+	if (unlikely(ctx->last_cmd[ap->port_no] == ATA_CMD_ID_ATA))
+		xgene_ahci_restart_engine(ap);
+
+	rc = ahci_qc_issue(qc);
+
+	/* Save the last command issued */
+	ctx->last_cmd[ap->port_no] = qc->tf.command;
+
+	return rc;
+}
+
 /**
  * xgene_ahci_read_id - Read ID data from the specified device
  * @dev: device
@@ -104,14 +149,12 @@ static int xgene_ahci_init_memram(struct xgene_ahci_context *ctx)
  * @id: data buffer
  *
  * This custom read ID function is required due to the fact that the HW
- * does not support DEVSLP and the controller state machine may get stuck
- * after processing the ID query command.
+ * does not support DEVSLP.
  */
 static unsigned int xgene_ahci_read_id(struct ata_device *dev,
 				       struct ata_taskfile *tf, u16 *id)
 {
 	u32 err_mask;
-	void __iomem *port_mmio = ahci_port_base(dev->link->ap);
 
 	err_mask = ata_do_dev_read_id(dev, tf, id);
 	if (err_mask)
@@ -133,16 +176,6 @@ static unsigned int xgene_ahci_read_id(struct ata_device *dev,
 	 */
 	id[ATA_ID_FEATURE_SUPP] &= ~(1 << 8);
 
-	/*
-	 * Due to HW errata, restart the port if no other command active.
-	 * Otherwise the controller may get stuck.
-	 */
-	if (!readl(port_mmio + PORT_CMD_ISSUE)) {
-		writel(PORT_CMD_FIS_RX, port_mmio + PORT_CMD);
-		readl(port_mmio + PORT_CMD);	/* Force a barrier */
-		writel(PORT_CMD_FIS_RX | PORT_CMD_START, port_mmio + PORT_CMD);
-		readl(port_mmio + PORT_CMD);	/* Force a barrier */
-	}
 	return 0;
 }
 
@@ -300,6 +333,7 @@ static struct ata_port_operations xgene_ahci_ops = {
 	.host_stop = xgene_ahci_host_stop,
 	.hardreset = xgene_ahci_hardreset,
 	.read_id = xgene_ahci_read_id,
+	.qc_issue = xgene_ahci_qc_issue,
 };
 
 static const struct ata_port_info xgene_ahci_port_info = {