sata_fsl: add support for interrupt coalsecing feature

Adds support for interrupt coalescing feature to reduce interrupt events.
Provides a mechanism of adjusting coalescing count and timeout tick by sysfs
at runtime, so that tradeoff of latency and CPU load can be made depending
on different applications.

Signed-off-by: Qiang Liu <qiang.liu@freescale.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/sata_fsl.c b/drivers/ata/sata_fsl.c
index 0120b0d1e9a5aa838cee9a7347992377012d6c8c..d6577b93bee3735a8eebf47a38f64dcc72aac182 100644 (file)
--- a/drivers/ata/sata_fsl.c
+++ b/drivers/ata/sata_fsl.c
@@ -6,7 +6,7 @@
  * Author: Ashish Kalra <ashish.kalra@freescale.com>
  * Li Yang <leoli@freescale.com>
  *
- * Copyright (c) 2006-2007, 2011 Freescale Semiconductor, Inc.
+ * Copyright (c) 2006-2007, 2011-2012 Freescale Semiconductor, Inc.
  *
  * This program is free software; you can redistribute  it and/or modify it
  * under  the terms of  the GNU General  Public License as published by the
@@ -26,6 +26,15 @@
 #include <asm/io.h>
 #include <linux/of_platform.h>
 
+static unsigned int intr_coalescing_count;
+module_param(intr_coalescing_count, int, S_IRUGO);
+MODULE_PARM_DESC(intr_coalescing_count,
+                                "INT coalescing count threshold (1..31)");
+
+static unsigned int intr_coalescing_ticks;
+module_param(intr_coalescing_ticks, int, S_IRUGO);
+MODULE_PARM_DESC(intr_coalescing_ticks,
+                                "INT coalescing timer threshold in AHB ticks");
 /* Controller information */
 enum {
        SATA_FSL_QUEUE_DEPTH    = 16,
@@ -82,6 +91,16 @@ enum {
        SATA_FSL_IRQ_FLAG       = IRQF_SHARED,
 };
 
+/*
+ * Interrupt Coalescing Control Register bitdefs  */
+enum {
+       ICC_MIN_INT_COUNT_THRESHOLD     = 1,
+       ICC_MAX_INT_COUNT_THRESHOLD     = ((1 << 5) - 1),
+       ICC_MIN_INT_TICKS_THRESHOLD     = 0,
+       ICC_MAX_INT_TICKS_THRESHOLD     = ((1 << 19) - 1),
+       ICC_SAFE_INT_TICKS              = 1,
+};
+
 /*
 * Host Controller command register set - per port
 */
@@ -263,8 +282,65 @@ struct sata_fsl_host_priv {
        void __iomem *csr_base;
        int irq;
        int data_snoop;
+       struct device_attribute intr_coalescing;
 };
 
+static void fsl_sata_set_irq_coalescing(struct ata_host *host,
+               unsigned int count, unsigned int ticks)
+{
+       struct sata_fsl_host_priv *host_priv = host->private_data;
+       void __iomem *hcr_base = host_priv->hcr_base;
+
+       if (count > ICC_MAX_INT_COUNT_THRESHOLD)
+               count = ICC_MAX_INT_COUNT_THRESHOLD;
+       else if (count < ICC_MIN_INT_COUNT_THRESHOLD)
+               count = ICC_MIN_INT_COUNT_THRESHOLD;
+
+       if (ticks > ICC_MAX_INT_TICKS_THRESHOLD)
+               ticks = ICC_MAX_INT_TICKS_THRESHOLD;
+       else if ((ICC_MIN_INT_TICKS_THRESHOLD == ticks) &&
+                       (count > ICC_MIN_INT_COUNT_THRESHOLD))
+               ticks = ICC_SAFE_INT_TICKS;
+
+       spin_lock(&host->lock);
+       iowrite32((count << 24 | ticks), hcr_base + ICC);
+
+       intr_coalescing_count = count;
+       intr_coalescing_ticks = ticks;
+       spin_unlock(&host->lock);
+
+       DPRINTK("intrrupt coalescing, count = 0x%x, ticks = %x\n",
+                       intr_coalescing_count, intr_coalescing_ticks);
+       DPRINTK("ICC register status: (hcr base: 0x%x) = 0x%x\n",
+                       hcr_base, ioread32(hcr_base + ICC));
+}
+
+static ssize_t fsl_sata_intr_coalescing_show(struct device *dev,
+               struct device_attribute *attr, char *buf)
+{
+       return sprintf(buf, "%d %d\n",
+                       intr_coalescing_count, intr_coalescing_ticks);
+}
+
+static ssize_t fsl_sata_intr_coalescing_store(struct device *dev,
+               struct device_attribute *attr,
+               const char *buf, size_t count)
+{
+       unsigned int coalescing_count,  coalescing_ticks;
+
+       if (sscanf(buf, "%d%d",
+                               &coalescing_count,
+                               &coalescing_ticks) != 2) {
+               printk(KERN_ERR "fsl-sata: wrong parameter format.\n");
+               return -EINVAL;
+       }
+
+       fsl_sata_set_irq_coalescing(dev_get_drvdata(dev),
+                       coalescing_count, coalescing_ticks);
+
+       return strlen(buf);
+}
+
 static inline unsigned int sata_fsl_tag(unsigned int tag,
                                        void __iomem *hcr_base)
 {
@@ -346,10 +422,10 @@ static unsigned int sata_fsl_fill_sg(struct ata_queued_cmd *qc, void *cmd_desc,
                        (unsigned long long)sg_addr, sg_len);
 
                /* warn if each s/g element is not dword aligned */
-               if (sg_addr & 0x03)
+               if (unlikely(sg_addr & 0x03))
                        ata_port_err(qc->ap, "s/g addr unaligned : 0x%llx\n",
                                     (unsigned long long)sg_addr);
-               if (sg_len & 0x03)
+               if (unlikely(sg_len & 0x03))
                        ata_port_err(qc->ap, "s/g len unaligned : 0x%x\n",
                                     sg_len);
 
@@ -1245,6 +1321,13 @@ static int sata_fsl_init_controller(struct ata_host *host)
        iowrite32(0x00000FFFF, hcr_base + CE);
        iowrite32(0x00000FFFF, hcr_base + DE);
 
+       /*
+        * reset the number of command complete bits which will cause the
+        * interrupt to be signaled
+        */
+       fsl_sata_set_irq_coalescing(host, intr_coalescing_count,
+                       intr_coalescing_ticks);
+
        /*
         * host controller will be brought on-line, during xx_port_start()
         * callback, that should also initiate the OOB, COMINIT sequence
@@ -1309,7 +1392,7 @@ static int sata_fsl_probe(struct platform_device *ofdev)
        void __iomem *csr_base = NULL;
        struct sata_fsl_host_priv *host_priv = NULL;
        int irq;
-       struct ata_host *host;
+       struct ata_host *host = NULL;
        u32 temp;
 
        struct ata_port_info pi = sata_fsl_port_info[0];
@@ -1356,6 +1439,10 @@ static int sata_fsl_probe(struct platform_device *ofdev)
 
        /* allocate host structure */
        host = ata_host_alloc_pinfo(&ofdev->dev, ppi, SATA_FSL_MAX_PORTS);
+       if (!host) {
+               retval = -ENOMEM;
+               goto error_exit_with_cleanup;
+       }
 
        /* host->iomap is not used currently */
        host->private_data = host_priv;
@@ -1373,10 +1460,24 @@ static int sata_fsl_probe(struct platform_device *ofdev)
 
        dev_set_drvdata(&ofdev->dev, host);
 
+       host_priv->intr_coalescing.show = fsl_sata_intr_coalescing_show;
+       host_priv->intr_coalescing.store = fsl_sata_intr_coalescing_store;
+       sysfs_attr_init(&host_priv->intr_coalescing.attr);
+       host_priv->intr_coalescing.attr.name = "intr_coalescing";
+       host_priv->intr_coalescing.attr.mode = S_IRUGO | S_IWUSR;
+       retval = device_create_file(host->dev, &host_priv->intr_coalescing);
+       if (retval)
+               goto error_exit_with_cleanup;
+
        return 0;
 
 error_exit_with_cleanup:
 
+       if (host) {
+               dev_set_drvdata(&ofdev->dev, NULL);
+               ata_host_detach(host);
+       }
+
        if (hcr_base)
                iounmap(hcr_base);
        if (host_priv)
@@ -1390,6 +1491,8 @@ static int sata_fsl_remove(struct platform_device *ofdev)
        struct ata_host *host = dev_get_drvdata(&ofdev->dev);
        struct sata_fsl_host_priv *host_priv = host->private_data;
 
+       device_remove_file(&ofdev->dev, &host_priv->intr_coalescing);
+
        ata_host_detach(host);
 
        dev_set_drvdata(&ofdev->dev, NULL);