[PATCH v4 3/3] cpufreq: brcmstb-avs-cpufreq: add debugfs support

Markus Mayer
2016-10-14T16:05:21Z

In order to aid debugging, we add a debugfs interface to the driver
that allows direct interaction with the AVS co-processor.

The debugfs interface provides a means for reading all and writing some
of the mailbox registers directly from the shell prompt and enables a
user to execute the communications protocol between ARM CPU and AVS CPU
step-by-step.

This interface should be used for debugging purposes only.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
---

** Re-send with author fixed. **

drivers/cpufreq/Kconfig.arm | 10 ++
drivers/cpufreq/brcmstb-avs-cpufreq.c | 323 +++++++++++++++++++++++++++++++++-
2 files changed, 332 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index d4e3795..43f261e 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -23,6 +23,16 @@ config ARM_BRCMSTB_AVS_CPUFREQ

Say Y, if you have a Broadcom SoC with AVS support for DFS or DVFS.

+config ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
+ bool "Broadcom STB AVS CPUfreq driver sysfs debug capability"
+ depends on ARM_BRCMSTB_AVS_CPUFREQ
+ help
+ Enabling this option turns on debug support via sysfs under
+ /sys/kernel/debug/brcmstb-avs-cpufreq. It is possible to read all and
+ write some AVS mailbox registers through sysfs entries.
+
+ If in doubt, say N.
+
config ARM_DT_BL_CPUFREQ
tristate "Generic probing via DT for ARM big LITTLE CPUfreq driver"
depends on ARM_BIG_LITTLE_CPUFREQ && OF
diff --git a/drivers/cpufreq/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c
index 4415fa0..b761d54 100644
--- a/drivers/cpufreq/brcmstb-avs-cpufreq.c
+++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c
@@ -49,6 +49,13 @@
#include <linux/platform_device.h>
#include <linux/semaphore.h>

+#ifdef CONFIG_ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
+#include <linux/ctype.h>
+#include <linux/debugfs.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#endif
+
/* Max number of arguments AVS calls take */
#define AVS_MAX_CMD_ARGS 4
/*
@@ -175,11 +182,88 @@ struct private_data {
void __iomem *base;
void __iomem *avs_intr_base;
struct device *dev;
+#ifdef CONFIG_ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
+ struct dentry *debugfs;
+#endif
struct completion done;
struct semaphore sem;
struct pmap pmap;
};

+#ifdef CONFIG_ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
+
+enum debugfs_format {
+ DEBUGFS_NORMAL,
+ DEBUGFS_FLOAT,
+ DEBUGFS_REV,
+};
+
+struct debugfs_data {
+ struct debugfs_entry *entry;
+ struct private_data *priv;
+};
+
+struct debugfs_entry {
+ char *name;
+ u32 offset;
+ fmode_t mode;
+ enum debugfs_format format;
+};
+
+#define DEBUGFS_ENTRY(name, mode, format) { \
+ #name, AVS_MBOX_##name, mode, format \
+}
+
+/*
+ * These are used for debugfs only. Otherwise we use AVS_MBOX_PARAM() directly.
+ */
+#define AVS_MBOX_PARAM1 AVS_MBOX_PARAM(0)
+#define AVS_MBOX_PARAM2 AVS_MBOX_PARAM(1)
+#define AVS_MBOX_PARAM3 AVS_MBOX_PARAM(2)
+#define AVS_MBOX_PARAM4 AVS_MBOX_PARAM(3)
+
+/*
+ * This table stores the name, access permissions and offset for each hardware
+ * register and is used to generate debugfs entries.
+ */
+static struct debugfs_entry debugfs_entries[] = {
+ DEBUGFS_ENTRY(COMMAND, S_IWUSR, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(STATUS, S_IWUSR, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(VOLTAGE0, 0, DEBUGFS_FLOAT),
+ DEBUGFS_ENTRY(TEMP0, 0, DEBUGFS_FLOAT),
+ DEBUGFS_ENTRY(PV0, 0, DEBUGFS_FLOAT),
+ DEBUGFS_ENTRY(MV0, 0, DEBUGFS_FLOAT),
+ DEBUGFS_ENTRY(PARAM1, S_IWUSR, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(PARAM2, S_IWUSR, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(PARAM3, S_IWUSR, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(PARAM4, S_IWUSR, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(REVISION, 0, DEBUGFS_REV),
+ DEBUGFS_ENTRY(PSTATE, 0, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(HEARTBEAT, 0, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(MAGIC, S_IWUSR, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(SIGMA_HVT, 0, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(SIGMA_SVT, 0, DEBUGFS_NORMAL),
+ DEBUGFS_ENTRY(VOLTAGE1, 0, DEBUGFS_FLOAT),
+ DEBUGFS_ENTRY(TEMP1, 0, DEBUGFS_FLOAT),
+ DEBUGFS_ENTRY(PV1, 0, DEBUGFS_FLOAT),
+ DEBUGFS_ENTRY(MV1, 0, DEBUGFS_FLOAT),
+ DEBUGFS_ENTRY(FREQUENCY, 0, DEBUGFS_NORMAL),
+};
+
+static int brcm_avs_target_index(struct cpufreq_policy *, unsigned int);
+
+static char *__strtolower(char *s)
+{
+ char *p;
+
+ for (p = s; *p; p++)
+ *p = tolower(*p);
+
+ return s;
+}
+
+#endif /* CONFIG_ARM_BRCMSTB_AVS_CPUFREQ_DEBUG */
+
static void __iomem *__map_region(const char *name)
{
struct device_node *np;
@@ -432,6 +516,238 @@ brcm_avs_get_freq_table(struct device *dev, struct private_data *priv)
return table;
}

+#ifdef CONFIG_ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
+
+#define MANT(x) (unsigned int)(abs((x)) / 1000)
+#define FRAC(x) (unsigned int)(abs((x)) - abs((x)) / 1000 * 1000)
+
+static int brcm_avs_debug_show(struct seq_file *s, void *data)
+{
+ struct debugfs_data *dbgfs = s->private;
+ void __iomem *base;
+ u32 val, offset;
+
+ if (!dbgfs) {
+ seq_puts(s, "No device pointer\n");
+ return 0;
+ }
+
+ base = dbgfs->priv->base;
+ offset = dbgfs->entry->offset;
+ val = readl(base + offset);
+ switch (dbgfs->entry->format) {
+ case DEBUGFS_NORMAL:
+ seq_printf(s, "%u\n", val);
+ break;
+ case DEBUGFS_FLOAT:
+ seq_printf(s, "%d.%03d\n", MANT(val), FRAC(val));
+ break;
+ case DEBUGFS_REV:
+ seq_printf(s, "%c.%c.%c.%c\n", (val >> 24 & 0xff),
+ (val >> 16 & 0xff), (val >> 8 & 0xff),
+ val & 0xff);
+ break;
+ }
+ seq_printf(s, "0x%08x\n", val);
+
+ return 0;
+}
+
+#undef MANT
+#undef FRAC
+
+static ssize_t brcm_avs_seq_write(struct file *file, const char __user *buf,
+ size_t size, loff_t *ppos)
+{
+ struct seq_file *s = file->private_data;
+ struct debugfs_data *dbgfs = s->private;
+ struct private_data *priv = dbgfs->priv;
+ void __iomem *base, *avs_intr_base;
+ bool use_issue_command = false;
+ unsigned long val, offset;
+ char str[128];
+ int ret;
+ char *str_ptr = str;
+
+ if (size >= sizeof(str))
+ return -E2BIG;
+
+ memset(str, 0, sizeof(str));
+ ret = copy_from_user(str, buf, size);
+ if (ret)
+ return ret;
+
+ base = priv->base;
+ avs_intr_base = priv->avs_intr_base;
+ offset = dbgfs->entry->offset;
+ /*
+ * Special case writing to "command" entry only: if the string starts
+ * with a 'c', we use the driver's __issue_avs_command() function.
+ * Otherwise, we perform a raw write. This should allow testing of raw
+ * access as well as using the higher level function. (Raw access
+ * doesn't clear the firmware return status after issuing the command.)
+ */
+ if (str_ptr[0] == 'c' && offset == AVS_MBOX_COMMAND) {
+ use_issue_command = true;
+ str_ptr++;
+ }
+ if (kstrtoul(str_ptr, 0, &val) != 0)
+ return -EINVAL;
+
+ /*
+ * Setting the P-state is a special case. We need to update the CPU
+ * frequency we report.
+ */
+ if (val == AVS_CMD_SET_PSTATE) {
+ struct cpufreq_policy *policy;
+ unsigned int pstate;
+
+ policy = cpufreq_cpu_get(smp_processor_id());
+ /* Read back the P-state we are about to set */
+ pstate = readl(base + AVS_MBOX_PARAM(0));
+ if (use_issue_command) {
+ ret = brcm_avs_target_index(policy, pstate);
+ return ret ? ret : size;
+ }
+ policy->cur = policy->freq_table[pstate].frequency;
+ }
+
+ if (use_issue_command) {
+ ret = __issue_avs_command(priv, val, false, NULL);
+ } else {
+ /* Locking here is not perfect, but is only for debug. */
+ ret = down_interruptible(&priv->sem);
+ if (ret)
+ return ret;
+
+ writel(val, base + offset);
+ /* We have to wake up the firmware to process a command. */
+ if (offset == AVS_MBOX_COMMAND)
+ writel(AVS_CPU_L2_INT_MASK,
+ avs_intr_base + AVS_CPU_L2_SET0);
+ up(&priv->sem);
+ }
+
+ return ret ? ret : size;
+}
+
+static struct debugfs_entry *__find_debugfs_entry(const char *name)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(debugfs_entries); i++)
+ if (strcasecmp(debugfs_entries[i].name, name) == 0)
+ return &debugfs_entries[i];
+
+ return NULL;
+}
+
+static int brcm_avs_debug_open(struct inode *inode, struct file *file)
+{
+ struct debugfs_data *data;
+ fmode_t fmode;
+ int ret;
+
+ /*
+ * seq_open(), which is called by single_open(), clears "write" access.
+ * We need write access to some files, so we preserve our access mode
+ * and restore it.
+ */
+ fmode = file->f_mode;
+ /*
+ * Check access permissions even for root. We don't want to be writing
+ * to read-only registers. Access for regular users has already been
+ * checked by the VFS layer.
+ */
+ if ((fmode & FMODE_WRITER) && !(inode->i_mode & S_IWUSR))
+ return -EACCES;
+
+ data = kmalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+ /*
+ * We use the same file system operations for all our debug files. To
+ * produce specific output, we look up the file name upon opening a
+ * debugfs entry and map it to a memory offset. This offset is then used
+ * in the generic "show" function to read a specific register.
+ */
+ data->entry = __find_debugfs_entry(file->f_path.dentry->d_iname);
+ data->priv = inode->i_private;
+
+ ret = single_open(file, brcm_avs_debug_show, data);
+ if (ret)
+ kfree(data);
+ file->f_mode = fmode;
+
+ return ret;
+}
+
+static int brcm_avs_debug_release(struct inode *inode, struct file *file)
+{
+ struct seq_file *seq_priv = file->private_data;
+ struct debugfs_data *data = seq_priv->private;
+
+ kfree(data);
+ return single_release(inode, file);
+}
+
+static const struct file_operations brcm_avs_debug_ops = {
+ .open = brcm_avs_debug_open,
+ .read = seq_read,
+ .write = brcm_avs_seq_write,
+ .llseek = seq_lseek,
+ .release = brcm_avs_debug_release,
+};
+
+static void brcm_avs_cpufreq_debug_init(struct platform_device *pdev)
+{
+ struct private_data *priv = platform_get_drvdata(pdev);
+ struct dentry *dir;
+ int i;
+
+ if (!priv)
+ return;
+
+ dir = debugfs_create_dir(BRCM_AVS_CPUFREQ_NAME, NULL);
+ if (IS_ERR_OR_NULL(dir))
+ return;
+ priv->debugfs = dir;
+
+ for (i = 0; i < ARRAY_SIZE(debugfs_entries); i++) {
+ /*
+ * The DEBUGFS_ENTRY macro generates uppercase strings. We
+ * convert them to lowercase before creating the debugfs
+ * entries.
+ */
+ char *entry = __strtolower(debugfs_entries[i].name);
+ fmode_t mode = debugfs_entries[i].mode;
+
+ if (!debugfs_create_file(entry, S_IFREG | S_IRUGO | mode,
+ dir, priv, &brcm_avs_debug_ops)) {
+ priv->debugfs = NULL;
+ debugfs_remove_recursive(dir);
+ break;
+ }
+ }
+}
+
+static void brcm_avs_cpufreq_debug_exit(struct platform_device *pdev)
+{
+ struct private_data *priv = platform_get_drvdata(pdev);
+
+ if (priv && priv->debugfs) {
+ debugfs_remove_recursive(priv->debugfs);
+ priv->debugfs = NULL;
+ }
+}
+
+#else
+
+static void brcm_avs_cpufreq_debug_init(struct platform_device *pdev) {}
+static void brcm_avs_cpufreq_debug_exit(struct platform_device *pdev) {}
+
+#endif /* CONFIG_ARM_BRCMSTB_AVS_CPUFREQ_DEBUG */
+
/*
* To ensure the right firmware is running we need to
* - check the MAGIC matches what we expect
@@ -694,8 +1010,11 @@ static int brcm_avs_cpufreq_probe(struct platform_device *pdev)
return ret;

brcm_avs_driver.driver_data = pdev;
+ ret = cpufreq_register_driver(&brcm_avs_driver);
+ if (!ret)
+ brcm_avs_cpufreq_debug_init(pdev);

- return cpufreq_register_driver(&brcm_avs_driver);
+ return ret;
}

static int brcm_avs_cpufreq_remove(struct platform_device *pdev)
@@ -707,6 +1026,8 @@ static int brcm_avs_cpufreq_remove(struct platform_device *pdev)
if (ret)
return ret;

+ brcm_avs_cpufreq_debug_exit(pdev);
+
priv = platform_get_drvdata(pdev);
iounmap(priv->base);
iounmap(priv->avs_intr_base);
--
2.7.4