ahci_xgene: Implement the xgene_ahci_poll_reg_val to support PMP.

This patch implements the function xgene_ahci_poll_reg_val
to poll PxCI for multiple IDENTIFY DEVICE commands to finish before
restarting the DMA engine.

Signed-off-by: Suman Tripathi <stripathi@apm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 54 insertions, 2 deletions

diff --git a/drivers/ata/ahci_xgene.c b/drivers/ata/ahci_xgene.c
index cbcd20810355..afa9c03ecfd6 100644
--- a/drivers/ata/ahci_xgene.c
+++ b/drivers/ata/ahci_xgene.c
@@ -105,17 +105,69 @@ static int xgene_ahci_init_memram(struct xgene_ahci_context *ctx)
 }
 
 /**
+ * xgene_ahci_poll_reg_val- Poll a register on a specific value.
+ * @ap : ATA port of interest.
+ * @reg : Register of interest.
+ * @val : Value to be attained.
+ * @interval : waiting interval for polling.
+ * @timeout : timeout for achieving the value.
+ */
+static int xgene_ahci_poll_reg_val(struct ata_port *ap,
+                                   void __iomem *reg, unsigned
+                                   int val, unsigned long interval,
+                                   unsigned long timeout)
+{
+        unsigned long deadline;
+        unsigned int tmp;
+
+        tmp = ioread32(reg);
+        deadline = ata_deadline(jiffies, timeout);
+
+        while (tmp != val && time_before(jiffies, deadline)) {
+                ata_msleep(ap, interval);
+                tmp = ioread32(reg);
+        }
+
+        return tmp;
+}
+
+/**
  * xgene_ahci_restart_engine - Restart the dma engine.
  * @ap : ATA port of interest
  *
- * Restarts the dma engine inside the controller.
+ * Waits for completion of multiple commands and 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;
+        struct ahci_port_priv *pp = ap->private_data;
+        void __iomem *port_mmio = ahci_port_base(ap);
+        u32 fbs;
+
+        /*
+         * In case of PMP multiple IDENTIFY DEVICE commands can be
+         * issued inside PxCI. So need to poll PxCI for the
+         * completion of outstanding IDENTIFY DEVICE commands before
+         * we restart the DMA engine.
+         */
+        if (xgene_ahci_poll_reg_val(ap, port_mmio +
+                                    PORT_CMD_ISSUE, 0x0, 1, 100))
+                  return -EBUSY;
 
         ahci_stop_engine(ap);
         ahci_start_fis_rx(ap);
+
+        /*
+         * Enable the PxFBS.FBS_EN bit as it
+         * gets cleared due to stopping the engine.
+         */
+        if (pp->fbs_supported) {
+                fbs = readl(port_mmio + PORT_FBS);
+                writel(fbs | PORT_FBS_EN, port_mmio + PORT_FBS);
+                fbs = readl(port_mmio + PORT_FBS);
+        }
+
         hpriv->start_engine(ap);
 
         return 0;
@@ -374,7 +426,7 @@ static struct ata_port_operations xgene_ahci_ops = {
 };
 
 static const struct ata_port_info xgene_ahci_port_info = {
-        .flags = AHCI_FLAG_COMMON,
+        .flags = AHCI_FLAG_COMMON | ATA_FLAG_PMP,
         .pio_mask = ATA_PIO4,
         .udma_mask = ATA_UDMA6,
         .port_ops = &xgene_ahci_ops,