pinctrl/pinconfig: add debug interface

This update adds a debugfs interface to modify a pin configuration
for a given state in the pinctrl map. This allows to modify the
configuration for a non-active state, typically sleep state.
This configuration is not applied right away, but only when the state
will be entered.

This solution is mandated for us by HW validation: in order
to test and verify several pin configurations during sleep without
recompiling the software.

Change log in this patch set;
Take into account latest feedback from Stephen Warren:
- stale comments update
- improved code efficiency and readibility
- limit size of global variable pinconf_dbg_conf
- remove req_type as it can easily be added later when
add/delete requests support is implemented

Signed-off-by: Laurent Meunier <laurent.meunier@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

2 files changed, 238 insertions, 0 deletions

diff --git a/drivers/pinctrl/pinconf.c b/drivers/pinctrl/pinconf.c
index baee2cc46a17..6f14b62ae8ba 100644
--- a/drivers/pinctrl/pinconf.c
+++ b/drivers/pinctrl/pinconf.c
@@ -17,6 +17,7 @@
 #include <linux/slab.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
+#include <linux/uaccess.h>
 #include <linux/pinctrl/machine.h>
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/pinctrl/pinconf.h>
@@ -574,6 +575,235 @@ static const struct file_operations pinconf_groups_ops = {
         .release        = single_release,
 };
 
+#define MAX_NAME_LEN 15
+
+struct dbg_cfg {
+        enum pinctrl_map_type map_type;
+        char dev_name[MAX_NAME_LEN+1];
+        char state_name[MAX_NAME_LEN+1];
+        char pin_name[MAX_NAME_LEN+1];
+};
+
+/*
+ * Goal is to keep this structure as global in order to simply read the
+ * pinconf-config file after a write to check config is as expected
+ */
+static struct dbg_cfg pinconf_dbg_conf;
+
+/**
+ * pinconf_dbg_config_print() - display the pinctrl config from the pinctrl
+ * map, of the dev/pin/state that was last written to pinconf-config file.
+ * @s: string filled in  with config description
+ * @d: not used
+ */
+static int pinconf_dbg_config_print(struct seq_file *s, void *d)
+{
+        struct pinctrl_maps *maps_node;
+        const struct pinctrl_map *map;
+        struct pinctrl_dev *pctldev = NULL;
+        const struct pinconf_ops *confops = NULL;
+        const struct pinctrl_map_configs *configs;
+        struct dbg_cfg *dbg = &pinconf_dbg_conf;
+        int i, j;
+        bool found = false;
+        unsigned long config;
+
+        mutex_lock(&pinctrl_mutex);
+
+        /* Parse the pinctrl map and look for the elected pin/state */
+        for_each_maps(maps_node, i, map) {
+                if (map->type != dbg->map_type)
+                        continue;
+                if (strcmp(map->dev_name, dbg->dev_name))
+                        continue;
+                if (strcmp(map->name, dbg->state_name))
+                        continue;
+
+                for (j = 0; j < map->data.configs.num_configs; j++) {
+                        if (!strcmp(map->data.configs.group_or_pin,
+                                        dbg->pin_name)) {
+                                /*
+                                 * We found the right pin / state, read the
+                                 * config and he pctldev for later use
+                                 */
+                                configs = &map->data.configs;
+                                pctldev = get_pinctrl_dev_from_devname
+                                        (map->ctrl_dev_name);
+                                found = true;
+                                break;
+                        }
+                }
+        }
+
+        if (!found) {
+                seq_printf(s, "No config found for dev/state/pin, expected:\n");
+                seq_printf(s, "Searched dev:%s\n", dbg->dev_name);
+                seq_printf(s, "Searched state:%s\n", dbg->state_name);
+                seq_printf(s, "Searched pin:%s\n", dbg->pin_name);
+                seq_printf(s, "Use: modify config_pin <devname> "\
+                                "<state> <pinname> <value>\n");
+                goto exit;
+        }
+
+        config = *(configs->configs);
+        seq_printf(s, "Dev %s has config of %s in state %s: 0x%08lX\n",
+                        dbg->dev_name, dbg->pin_name,
+                        dbg->state_name, config);
+
+        if (pctldev)
+                confops = pctldev->desc->confops;
+
+        if (confops && confops->pin_config_config_dbg_show)
+                confops->pin_config_config_dbg_show(pctldev, s, config);
+
+exit:
+        mutex_unlock(&pinctrl_mutex);
+
+        return 0;
+}
+
+/**
+ * pinconf_dbg_config_write() - modify the pinctrl config in the pinctrl
+ * map, of a dev/pin/state entry based on user entries to pinconf-config
+ * @user_buf: contains the modification request with expected format:
+ *     modify config_pin <devicename> <state> <pinname> <newvalue>
+ * modify is literal string, alternatives like add/delete not supported yet
+ * config_pin is literal, alternatives like config_mux not supported yet
+ * <devicename> <state> <pinname> are values that should match the pinctrl-maps
+ * <newvalue> reflects the new config and is driver dependant
+ */
+static int pinconf_dbg_config_write(struct file *file,
+        const char __user *user_buf, size_t count, loff_t *ppos)
+{
+        struct pinctrl_maps *maps_node;
+        const struct pinctrl_map *map;
+        struct pinctrl_dev *pctldev = NULL;
+        const struct pinconf_ops *confops = NULL;
+        struct dbg_cfg *dbg = &pinconf_dbg_conf;
+        const struct pinctrl_map_configs *configs;
+        char config[MAX_NAME_LEN+1];
+        bool found = false;
+        char buf[128];
+        char *b = &buf[0];
+        int buf_size;
+        char *token;
+        int i;
+
+        /* Get userspace string and assure termination */
+        buf_size = min(count, (sizeof(buf)-1));
+        if (copy_from_user(buf, user_buf, buf_size))
+                return -EFAULT;
+        buf[buf_size] = 0;
+
+        /*
+         * need to parse entry and extract parameters:
+         * modify configs_pin devicename state pinname newvalue
+         */
+
+        /* Get arg: 'modify' */
+        token = strsep(&b, " ");
+        if (!token)
+                return -EINVAL;
+        if (strcmp(token, "modify"))
+                return -EINVAL;
+
+        /* Get arg type: "config_pin" type supported so far */
+        token = strsep(&b, " ");
+        if (!token)
+                return -EINVAL;
+        if (strcmp(token, "config_pin"))
+                return -EINVAL;
+        dbg->map_type = PIN_MAP_TYPE_CONFIGS_PIN;
+
+        /* get arg 'device_name' */
+        token = strsep(&b, " ");
+        if (token == NULL)
+                return -EINVAL;
+        if (strlen(token) >= MAX_NAME_LEN)
+                return -EINVAL;
+        strncpy(dbg->dev_name, token, MAX_NAME_LEN);
+
+        /* get arg 'state_name' */
+        token = strsep(&b, " ");
+        if (token == NULL)
+                return -EINVAL;
+        if (strlen(token) >= MAX_NAME_LEN)
+                return -EINVAL;
+        strncpy(dbg->state_name, token, MAX_NAME_LEN);
+
+        /* get arg 'pin_name' */
+        token = strsep(&b, " ");
+        if (token == NULL)
+                return -EINVAL;
+        if (strlen(token) >= MAX_NAME_LEN)
+                return -EINVAL;
+        strncpy(dbg->pin_name, token, MAX_NAME_LEN);
+
+        /* get new_value of config' */
+        token = strsep(&b, " ");
+        if (token == NULL)
+                return -EINVAL;
+        if (strlen(token) >= MAX_NAME_LEN)
+                return -EINVAL;
+        strncpy(config, token, MAX_NAME_LEN);
+
+        mutex_lock(&pinctrl_mutex);
+
+        /* Parse the pinctrl map and look for the selected dev/state/pin */