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Re: [PATCH] MIPS: Octeon: Adding driver to measure interrupt latency on

To: Venkat Subbiah <vsubbiah@caviumnetworks.com>
Subject: Re: [PATCH] MIPS: Octeon: Adding driver to measure interrupt latency on Octeon.
From: David Daney <ddaney@caviumnetworks.com>
Date: Fri, 29 Mar 2013 15:55:11 -0700
Cc: <linux-mips@linux-mips.org>, <ralf@linux-mips.org>
In-reply-to: <51561A75.4040601@caviumnetworks.com>
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On 03/29/2013 03:49 PM, Venkat Subbiah wrote:
I was wondering whether this patch got accepted upstream. How do you
usually got about checking whether a patch made it upstream?
Thanks,
Venkat


It did.

You can always look here:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/



On 12/01/2012 05:51 PM, vsubbiah@caviumnetworks.com wrote:
From: Venkat Subbiah <venkat.subbiah@cavium.com>

Signed-off-by: Venkat Subbiah <venkat.subbiah@cavium.com>
[Rewrote timeing calculations]
Signed-off-by: David Daney <david.daney@cavium.com>
---
  arch/mips/cavium-octeon/Kconfig   |    9 ++
  arch/mips/cavium-octeon/Makefile  |    1 +
  arch/mips/cavium-octeon/oct_ilm.c |  206
+++++++++++++++++++++++++++++++++++++
  3 files changed, 216 insertions(+)
  create mode 100644 arch/mips/cavium-octeon/oct_ilm.c

diff --git a/arch/mips/cavium-octeon/Kconfig
b/arch/mips/cavium-octeon/Kconfig
index 2f4f6d5..75a6df7 100644
--- a/arch/mips/cavium-octeon/Kconfig
+++ b/arch/mips/cavium-octeon/Kconfig
@@ -94,4 +94,13 @@ config SWIOTLB
      select NEED_SG_DMA_LENGTH
+config OCTEON_ILM
+    tristate "Module to measure interrupt latency using Octeon CIU
Timer"
+    help
+      This driver is a module to measure interrupt latency using the
+      the CIU Timers on Octeon.
+
+      To compile this driver as a module, choose M here.  The module
+      will be called octeon-ilm
+
  endif # CPU_CAVIUM_OCTEON
diff --git a/arch/mips/cavium-octeon/Makefile
b/arch/mips/cavium-octeon/Makefile
index bc96e29..614db10 100644
--- a/arch/mips/cavium-octeon/Makefile
+++ b/arch/mips/cavium-octeon/Makefile
@@ -18,6 +18,7 @@ obj-y += octeon-memcpy.o
  obj-y += executive/
  obj-$(CONFIG_SMP)                     += smp.o
+obj-$(CONFIG_OCTEON_ILM)              += oct_ilm.o
  DTS_FILES = octeon_3xxx.dts octeon_68xx.dts
  DTB_FILES = $(patsubst %.dts, %.dtb, $(DTS_FILES))
diff --git a/arch/mips/cavium-octeon/oct_ilm.c
b/arch/mips/cavium-octeon/oct_ilm.c
new file mode 100644
index 0000000..71b213d
--- /dev/null
+++ b/arch/mips/cavium-octeon/oct_ilm.c
@@ -0,0 +1,206 @@
+#include <linux/fs.h>
+#include <linux/interrupt.h>
+#include <asm/octeon/octeon.h>
+#include <asm/octeon/cvmx-ciu-defs.h>
+#include <asm/octeon/cvmx.h>
+#include <linux/debugfs.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+
+#define TIMER_NUM 3
+
+static bool reset_stats;
+
+struct latency_info {
+    u64 io_interval;
+    u64 cpu_interval;
+    u64 timer_start1;
+    u64 timer_start2;
+    u64 max_latency;
+    u64 min_latency;
+    u64 latency_sum;
+    u64 average_latency;
+    u64 interrupt_cnt;
+};
+
+static struct latency_info li;
+static struct dentry *dir;
+
+static int show_latency(struct seq_file *m, void *v)
+{
+    u64 cpuclk, avg, max, min;
+    struct latency_info curr_li = li;
+
+    cpuclk = octeon_get_clock_rate();
+
+    max = (curr_li.max_latency * 1000000000) / cpuclk;
+    min = (curr_li.min_latency * 1000000000) / cpuclk;
+    avg = (curr_li.latency_sum * 1000000000) / (cpuclk *
curr_li.interrupt_cnt);
+
+    seq_printf(m, "cnt: %10lld, avg: %7lld ns, max: %7lld ns, min:
%7lld ns\n",
+           curr_li.interrupt_cnt, avg, max, min);
+    return 0;
+}
+
+static int oct_ilm_open(struct inode *inode, struct file *file)
+{
+    return single_open(file, show_latency, NULL);
+}
+
+static const struct file_operations oct_ilm_ops = {
+    .open = oct_ilm_open,
+    .read = seq_read,
+    .llseek = seq_lseek,
+    .release = single_release,
+};
+
+static int reset_statistics(void *data, u64 value)
+{
+    reset_stats = true;
+    return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(reset_statistics_ops, NULL, reset_statistics,
"%llu\n");
+
+static int init_debufs(void)
+{
+    struct dentry *show_dentry;
+    dir = debugfs_create_dir("oct_ilm", 0);
+    if (!dir) {
+        pr_err("oct_ilm: failed to create debugfs entry oct_ilm\n");
+        return -1;
+    }
+
+    show_dentry = debugfs_create_file("statistics", 0222, dir, NULL,
+                      &oct_ilm_ops);
+    if (!show_dentry) {
+        pr_err("oct_ilm: failed to create debugfs entry
oct_ilm/statistics\n");
+        return -1;
+    }
+
+    show_dentry = debugfs_create_file("reset", 0222, dir, NULL,
+                      &reset_statistics_ops);
+    if (!show_dentry) {
+        pr_err("oct_ilm: failed to create debugfs entry
oct_ilm/reset\n");
+        return -1;
+    }
+
+    return 0;
+
+}
+
+static void init_latency_info(struct latency_info *li, int startup)
+{
+    /* interval in milli seconds after which the interrupt will
+     * be triggered
+     */
+    int interval = 1;
+
+    if (startup) {
+        /* Calculating by the amounts io clock and cpu clock would
+         *  increment in interval amount of ms
+         */
+        li->io_interval = (octeon_get_io_clock_rate() * interval) /
1000;
+        li->cpu_interval = (octeon_get_clock_rate() * interval) / 1000;
+    }
+    li->timer_start1 = 0;
+    li->timer_start2 = 0;
+    li->max_latency = 0;
+    li->min_latency = (u64)-1;
+    li->latency_sum = 0;
+    li->interrupt_cnt = 0;
+}
+
+
+static void start_timer(int timer, u64 interval)
+{
+    union cvmx_ciu_timx timx;
+    unsigned long flags;
+
+    timx.u64 = 0;
+    timx.s.one_shot = 1;
+    timx.s.len = interval;
+    raw_local_irq_save(flags);
+    li.timer_start1 = read_c0_cvmcount();
+    cvmx_write_csr(CVMX_CIU_TIMX(timer), timx.u64);
+    /* Read it back to force wait until register is written. */
+    timx.u64 = cvmx_read_csr(CVMX_CIU_TIMX(timer));
+    li.timer_start2 = read_c0_cvmcount();
+    raw_local_irq_restore(flags);
+}
+
+
+static irqreturn_t cvm_oct_ciu_timer_interrupt(int cpl, void *dev_id)
+{
+    u64 last_latency;
+    u64 last_int_cnt;
+
+    if (reset_stats) {
+        init_latency_info(&li, 0);
+        reset_stats = false;
+    } else {
+        last_int_cnt = read_c0_cvmcount();
+        last_latency = last_int_cnt - (li.timer_start1 +
li.cpu_interval);
+        li.interrupt_cnt++;
+        li.latency_sum += last_latency;
+        if (last_latency > li.max_latency)
+            li.max_latency = last_latency;
+        if (last_latency < li.min_latency)
+            li.min_latency = last_latency;
+    }
+    start_timer(TIMER_NUM, li.io_interval);
+    return IRQ_HANDLED;
+}
+
+static void disable_timer(int timer)
+{
+    union cvmx_ciu_timx timx;
+
+    timx.s.one_shot = 0;
+    timx.s.len = 0;
+    cvmx_write_csr(CVMX_CIU_TIMX(timer), timx.u64);
+    /* Read it back to force immediate write of timer register*/
+    timx.u64 = cvmx_read_csr(CVMX_CIU_TIMX(timer));
+}
+
+static __init int oct_ilm_module_init(void)
+{
+    int rc;
+    int irq = OCTEON_IRQ_TIMER0 + TIMER_NUM;
+
+    rc = init_debufs();
+    if (rc) {
+        WARN(1, "Could not create debugfs entries");
+        return rc;
+    }
+
+    rc = request_irq(irq, cvm_oct_ciu_timer_interrupt, IRQF_NO_THREAD,
+             "oct_ilm", 0);
+    if (rc) {
+        WARN(1, "Could not acquire IRQ %d", irq);
+        goto err_irq;
+    }
+
+    init_latency_info(&li, 1);
+    start_timer(TIMER_NUM, li.io_interval);
+
+    return 0;
+err_irq:
+    debugfs_remove_recursive(dir);
+    return rc;
+}
+
+static __exit void oct_ilm_module_exit(void)
+{
+    disable_timer(TIMER_NUM);
+    if (dir)
+        debugfs_remove_recursive(dir);
+    free_irq(OCTEON_IRQ_TIMER0 + TIMER_NUM, 0);
+}
+
+module_exit(oct_ilm_module_exit);
+module_init(oct_ilm_module_init);
+MODULE_AUTHOR("Venkat Subbiah, Cavium");
+MODULE_DESCRIPTION("Measures interrupt latency on Octeon chips.");
+MODULE_LICENSE("GPL");





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