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 at the same clock cycle.
Signed-off-by: Suman Tripathi <stripathi@xxxxxxx>
---
drivers/ata/ahci_xgene.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 84 insertions(+), 0 deletions(-)
diff --git a/drivers/ata/ahci_xgene.c b/drivers/ata/ahci_xgene.c
index 892ec74..60076a3 100644
--- a/drivers/ata/ahci_xgene.c
+++ b/drivers/ata/ahci_xgene.c
@@ -548,6 +548,89 @@ 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;
+ struct ahci_host_priv *hpriv;
+ unsigned int rc = 0;
+ void __iomem *mmio;
+ u32 irq_stat, irq_masked;
+
+ VPRINTK("ENTER\n");
+
+ hpriv = host->private_data;
+ mmio = hpriv->mmio;
+
+ /* sigh. 0xffffffff is a valid return from h/w */
+ irq_stat = readl(mmio + HOST_IRQ_STAT);
+ if (!irq_stat)
+ return IRQ_NONE;
+
+ irq_masked = irq_stat & hpriv->port_map;
+
+ spin_lock(&host->lock);
+
+ /*
+ * HOST_IRQ_STAT behaves as edge triggered latch meaning that
+ * it should be cleared before all the port events are cleared.
+ */
+ writel(irq_stat, mmio + HOST_IRQ_STAT);
+
+ rc = xgene_ahci_handle_broken_edge_irq(host, irq_masked);
+
+ spin_unlock(&host->lock);
+
+ VPRINTK("EXIT\n");
+
+ return IRQ_RETVAL(rc);
+
+}
+
static struct ata_port_operations xgene_ahci_v1_ops = {
.inherits = &ahci_ops,
.host_stop = xgene_ahci_host_stop,
@@ -780,6 +863,7 @@ skip_clk_phy:
break;
case XGENE_AHCI_V2:
hpriv->flags |= AHCI_HFLAG_YES_FBS;
+ hpriv->ahci_irq_intr = xgene_ahci_irq_intr;
break;
default:
break;
--
1.7.1
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