Re: [PATCH V2] AHCI: Workaround for ThunderX Errata#22536

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Hello.

On 2/13/2016 2:20 AM, tchalamarla@xxxxxxxxxxxxxxxxxx wrote:

From: Tirumalesh Chalamarla <tchalamarla@xxxxxxxxxxxxxxxxxx>

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

Signed-off-by: Tirumalesh Chalamarla <tchalamarla@xxxxxxxxxxxxxxxxxx>
---
  drivers/ata/Makefile        |  2 +-
  drivers/ata/ahci.c          |  3 ++
  drivers/ata/ahci.h          |  1 +
  drivers/ata/ahci_thunderx.c | 73 +++++++++++++++++++++++++++++++++++++++++++++
  4 files changed, 78 insertions(+), 1 deletion(-)
  create mode 100644 drivers/ata/ahci_thunderx.c

diff --git a/drivers/ata/Makefile b/drivers/ata/Makefile
index 1857952..a36e70d 100644
--- a/drivers/ata/Makefile
+++ b/drivers/ata/Makefile
@@ -2,7 +2,7 @@
  obj-$(CONFIG_ATA)		+= libata.o

  # non-SFF interface
-obj-$(CONFIG_SATA_AHCI)		+= ahci.o libahci.o
+obj-$(CONFIG_SATA_AHCI)		+= ahci.o libahci.o ahci_thunderx.o
  obj-$(CONFIG_SATA_ACARD_AHCI)	+= acard-ahci.o libahci.o
  obj-$(CONFIG_SATA_AHCI_PLATFORM) += ahci_platform.o libahci.o libahci_platform.o
  obj-$(CONFIG_SATA_FSL)		+= sata_fsl.o
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 546a369..76e310e 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1560,6 +1560,9 @@ 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;

+	if (pdev->vendor == 0x177d && pdev->device == 0xa01c)
+		ahci_thunderx_init(&pdev->dev, hpriv);
+
  	/* save initial config */
  	ahci_pci_save_initial_config(pdev, hpriv);

diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 167ba7e..77ae20d 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -425,6 +425,7 @@ void ahci_print_info(struct ata_host *host, const char *scc_s);
  int ahci_host_activate(struct ata_host *host, struct scsi_host_template *sht);
  void ahci_error_handler(struct ata_port *ap);
  u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked);
+void ahci_thunderx_init(struct device *dev, struct ahci_host_priv *hpriv);

  static inline void __iomem *__ahci_port_base(struct ata_host *host,
  					     unsigned int port_no)
diff --git a/drivers/ata/ahci_thunderx.c b/drivers/ata/ahci_thunderx.c
new file mode 100644
index 0000000..223e170
--- /dev/null
+++ b/drivers/ata/ahci_thunderx.c
@@ -0,0 +1,73 @@
+/*
+ * SATA glue for Cavium Thunder SOCs.
+ *
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2010-2016 Cavium Networks
+ *
+ */
+
+#include <linux/module.h>
+#include "ahci.h"
+#include "libata.h"
+
+static irqreturn_t ahci_thunderx_irq_intr(int irq, void *dev_instance)

   *_irq_intr() is a bit tautological.

+{
+	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;

   Why not do this in the initializers?

+
+	/* sigh.  0xffffffff is a valid return from h/w */
+	irq_stat = readl(mmio + HOST_IRQ_STAT);
+	if (!irq_stat)
+		return IRQ_NONE;
+redo:

   Closer to the next statement, please.

+
+	irq_masked = irq_stat & hpriv->port_map;
+
+	spin_lock(&host->lock);
+
+	rc = ahci_handle_port_intr(host, irq_masked);
+

   No need for empty line here.

+	if (!rc)
+		handled = 0;

   Doesn't this override the valid result in case of looping?

+
+	writel(irq_stat, mmio + HOST_IRQ_STAT);
+
+	/* 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
+	 */
+	irq_stat = readl(mmio + HOST_IRQ_STAT);
+
+	spin_unlock(&host->lock);
+
+	if (irq_stat)
+		goto redo;

   You can have a *do*/*while* loop, no need for *goto*.

+
+	VPRINTK("EXIT\n");
+
+	return IRQ_RETVAL(handled);
+}
+
+void ahci_thunderx_init(struct device *dev, struct ahci_host_priv *hpriv)
+{
+	hpriv->irq_handler = ahci_thunderx_irq_intr;
+}
+EXPORT_SYMBOL_GPL(ahci_thunderx_init);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Cavium, Inc. <support@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Cavium Inc. ThunderX sata config.");

MBR, Sergei

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