ahci_xgene: Implement the workaround to fix the missing of the edge interrupt for the HOST_IRQ_STAT.
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 8b8ccb6..8e3f7fa 100644
--- a/drivers/ata/ahci_xgene.c
+++ b/drivers/ata/ahci_xgene.c
@@ -548,6 +548,51 @@
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 @@
*/
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);