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Subject[PATCH V3] AHCI: Workaround for ThunderX Errata#22536
Date
From: Tirumalesh Chalamarla <tchalamarla@caviumnetworks.com>

Due to Errata in ThunderX, HOST_IRQ_STAT should be
cleared before leaving the interrupt handler.
The patch attempts to satisfy the need.

Changes from V2:
- removed newfile
- code is now under CONFIG_ARM64

Changes from V1:
- Rebased on top of libata/for-4.6
- Moved ThunderX intr handler to new file

Signed-off-by: Tirumalesh Chalamarla <tchalamarla@caviumnetworks.com>
---
drivers/ata/ahci.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 546a369..c8496fc 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1325,6 +1325,44 @@ static inline void ahci_gtf_filter_workaround(struct ata_host *host)
{}
#endif

+#ifdef CONFIG_ARM64
+/* Due to ERRATA#22536, ThunderX need to handle
+ * HOST_IRQ_STAT differently.
+ * Work around is to make sure all pending IRQs
+ * are served before leaving handler
+ */
+static irqreturn_t ahci_thunderx_irq_handler(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;
+ unsigned int handled = 1;
+
+ VPRINTK("ENTER\n");
+ hpriv = host->private_data;
+ mmio = hpriv->mmio;
+ irq_stat = readl(mmio + HOST_IRQ_STAT);
+ if (!irq_stat)
+ return IRQ_NONE;
+
+ do {
+ irq_masked = irq_stat & hpriv->port_map;
+ spin_lock(&host->lock);
+ rc = ahci_handle_port_intr(host, irq_masked);
+ if (!rc)
+ handled = 0;
+ writel(irq_stat, mmio + HOST_IRQ_STAT);
+ irq_stat = readl(mmio + HOST_IRQ_STAT);
+ spin_unlock(&host->lock);
+ } while (irq_stat);
+ VPRINTK("EXIT\n");
+
+ return IRQ_RETVAL(handled);
+}
+#endif
+
/*
* ahci_init_msix() - optionally enable per-port MSI-X otherwise defer
* to single msi.
@@ -1560,6 +1598,12 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
if (ahci_broken_devslp(pdev))
hpriv->flags |= AHCI_HFLAG_NO_DEVSLP;

+#ifdef CONFIG_ARM64
+ /* this should be done before save config*/
+ if (pdev->vendor == 0x177d && pdev->device == 0xa01c)
+ hpriv->irq_handler = ahci_thunderx_irq_handler;
+#endif
+
/* save initial config */
ahci_pci_save_initial_config(pdev, hpriv);

--
2.1.0
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