ahci_xgene: Implement the workaround to fix the missing of the edge interrupt for...

Due to H/W errata, the HOST_IRQ_STAT register misses the edge interrupt
when clearing the HOST_IRQ_STAT register and hardware reporting the
PORT_IRQ_STAT register happens to be at the same clock cycle.

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

diff --git a/drivers/ata/ahci_xgene.c b/drivers/ata/ahci_xgene.c
index 8b8ccb6434e21bdc778c56f5bd03e6c793ee5027..8e3f7faf00d383f8eea284fe122e90a44ee7ce40 100644 (file)
--- a/drivers/ata/ahci_xgene.c
+++ b/drivers/ata/ahci_xgene.c
@@ -548,6 +548,51 @@ softreset_retry:
        return rc;
 }
 
+/**
+ * xgene_ahci_handle_broken_edge_irq - Handle the broken irq.
+ * @ata_host: Host that recieved the irq
+ * @irq_masked: HOST_IRQ_STAT value
+ *
+ * For hardware with broken edge trigger latch
+ * the HOST_IRQ_STAT register misses the edge interrupt
+ * when clearing of HOST_IRQ_STAT register and hardware
+ * reporting the PORT_IRQ_STAT register at the
+ * same clock cycle.
+ * As such, the algorithm below outlines the workaround.
+ *
+ * 1. Read HOST_IRQ_STAT register and save the state.
+ * 2. Clear the HOST_IRQ_STAT register.
+ * 3. Read back the HOST_IRQ_STAT register.
+ * 4. If HOST_IRQ_STAT register equals to zero, then
+ *    traverse the rest of port's PORT_IRQ_STAT register
+ *    to check if an interrupt is triggered at that point else
+ *    go to step 6.
+ * 5. If PORT_IRQ_STAT register of rest ports is not equal to zero
+ *    then update the state of HOST_IRQ_STAT saved in step 1.
+ * 6. Handle port interrupts.
+ * 7. Exit
+ */
+static int xgene_ahci_handle_broken_edge_irq(struct ata_host *host,
+                                            u32 irq_masked)
+{
+       struct ahci_host_priv *hpriv = host->private_data;
+       void __iomem *port_mmio;
+       int i;
+
+       if (!readl(hpriv->mmio + HOST_IRQ_STAT)) {
+               for (i = 0; i < host->n_ports; i++) {
+                       if (irq_masked & (1 << i))
+                               continue;
+
+                       port_mmio = ahci_port_base(host->ports[i]);
+                       if (readl(port_mmio + PORT_IRQ_STAT))
+                               irq_masked |= (1 << i);
+               }
+       }
+
+       return ahci_handle_port_intr(host, irq_masked);
+}
+
 static irqreturn_t xgene_ahci_irq_intr(int irq, void *dev_instance)
 {
        struct ata_host *host = dev_instance;
@@ -576,7 +621,7 @@ static irqreturn_t xgene_ahci_irq_intr(int irq, void *dev_instance)
         */
        writel(irq_stat, mmio + HOST_IRQ_STAT);
 
-       rc = ahci_handle_port_intr(host, irq_masked);
+       rc = xgene_ahci_handle_broken_edge_irq(host, irq_masked);
 
        spin_unlock(&host->lock);