[PATCH v2] clk: Add support for setting clk_rate via debugfs

From: Geert Uytterhoeven
Date: Wed Aug 28 2019 - 09:23:17 EST


For testing, it is useful to be able to specify a clock rate manually.
As this is a dangerous feature, it is not enabled by default.
Users need to modify the source directly and #define
CLOCK_ALLOW_WRITE_DEBUGFS.

This follows the spirit of commit 09c6ecd394105c48 ("regmap: Add support
for writing to regmap registers via debugfs").

Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
Stephen: you suggested this approach in
https://lore.kernel.org/linux-clk/153029668040.143105.2059491089047180792@xxxxxxxxxxxxxxxxxxxxxxxxxx/

v2:
- Rebased.
---
drivers/clk/clk.c | 38 +++++++++++++++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 2ba52b8dafcc1cc5..5b3c915b9507634c 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -2990,6 +2990,41 @@ static int clk_dump_show(struct seq_file *s, void *data)
}
DEFINE_SHOW_ATTRIBUTE(clk_dump);

+#undef CLOCK_ALLOW_WRITE_DEBUGFS
+#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
+/*
+ * This can be dangerous, therefore don't provide any real compile time
+ * configuration option for this feature.
+ * People who want to use this will need to modify the source code directly.
+ */
+static int clk_rate_set(void *data, u64 val)
+{
+ struct clk_core *core = data;
+ int ret;
+
+ clk_prepare_lock();
+ ret = clk_core_set_rate_nolock(core, val);
+ clk_prepare_unlock();
+
+ return ret;
+}
+
+#define clk_rate_mode 0644
+#else
+#define clk_rate_set NULL
+#define clk_rate_mode 0444
+#endif
+
+static int clk_rate_get(void *data, u64 *val)
+{
+ struct clk_core *core = data;
+
+ *val = core->rate;
+ return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(clk_rate_fops, clk_rate_get, clk_rate_set, "%llu\n");
+
static const struct {
unsigned long flag;
const char *name;
@@ -3139,7 +3174,8 @@ static void clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
root = debugfs_create_dir(core->name, pdentry);
core->dentry = root;

- debugfs_create_ulong("clk_rate", 0444, root, &core->rate);
+ debugfs_create_file("clk_rate", clk_rate_mode, root, core,
+ &clk_rate_fops);
debugfs_create_file("clk_min_rate", 0444, root, core, &clk_min_rate_fops);
debugfs_create_file("clk_max_rate", 0444, root, core, &clk_max_rate_fops);
debugfs_create_ulong("clk_accuracy", 0444, root, &core->accuracy);
--
2.17.1