Re: [PATCH] clk: qcom: gfm-mux: use runtime pm while accessing registers

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On 21/03/2023 18:46, Stephen Boyd wrote:
Quoting Srinivas Kandagatla (2023-03-21 10:57:58)
gfm mux driver does support runtime pm but we never use it while
accessing registers. Looks like this driver was getting lucky and
totally depending on other drivers to leave the clk on.

Fix this by doing runtime pm while accessing registers.

Fixes: a2d8f507803e ("clk: qcom: Add support to LPASS AUDIO_CC Glitch Free Mux clocks")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Amit Pundir <amit.pundir@xxxxxxxxxx>

Is there a link to the report?

https://www.spinics.net/lists/stable/msg638380.html


Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
---
  drivers/clk/qcom/lpass-gfm-sm8250.c | 29 ++++++++++++++++++++++++++++-
  1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/qcom/lpass-gfm-sm8250.c b/drivers/clk/qcom/lpass-gfm-sm8250.c
index 96f476f24eb2..bcf0ea534f7f 100644
--- a/drivers/clk/qcom/lpass-gfm-sm8250.c
+++ b/drivers/clk/qcom/lpass-gfm-sm8250.c
@@ -38,14 +38,37 @@ struct clk_gfm {
  static u8 clk_gfm_get_parent(struct clk_hw *hw)
  {
         struct clk_gfm *clk = to_clk_gfm(hw);
+       int ret;
+       u8 parent;
+
+       ret = pm_runtime_resume_and_get(clk->priv->dev);
+       if (ret < 0 && ret != -EACCES) {
+               dev_err_ratelimited(clk->priv->dev,
+                                   "pm_runtime_resume_and_get failed in %s, ret %d\n",
+                                   __func__, ret);
+               return ret;
+       }
+
+       parent = readl(clk->gfm_mux) & clk->mux_mask;
+
+       pm_runtime_mark_last_busy(clk->priv->dev);
- return readl(clk->gfm_mux) & clk->mux_mask;
+       return parent;
  }
static int clk_gfm_set_parent(struct clk_hw *hw, u8 index)
  {
         struct clk_gfm *clk = to_clk_gfm(hw);
         unsigned int val;
+       int ret;
+
+       ret = pm_runtime_resume_and_get(clk->priv->dev);

Doesn't the clk framework already do this? Why do we need to do it
again?

You are right, clk core already does do pm_runtime_resume_and_get for set_parent.

this looks redundant here.


so we need only need to add this for get_parent

--srini

+       if (ret < 0 && ret != -EACCES) {
+               dev_err_ratelimited(clk->priv->dev,
+                                   "pm_runtime_resume_and_get failed in %s, ret %d\n",
+                                   __func__, ret);
+               return ret;
+       }
val = readl(clk->gfm_mux);




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