Re: [PATCH v6 3/4] clk: keystone: sci-clk: add restore_context() operation

[Nishanth Menon <nm@ti.com>]

On 14:21-20260427, Thomas Richard (TI) wrote:
> Implement the restore_context() operation to restore the clock rate and the
> clock parent state. The clock rate is saved in sci_clk struct during
> set_rate() and recalc_rate() operations. The parent index is saved in
> sci_clk struct during set_parent() operation. During clock registration,
> the core retrieves each clock’s parent using get_parent() operation to
> ensure the internal clock tree reflects the actual hardware state,
> including any configurations made by the bootloader. So we also save the
> parent index in get_parent().
> 
> Reviewed-by: Dhruva Gole <d-gole@ti.com>
> Reviewed-by: Kendall Willis <k-willis@ti.com>
> Signed-off-by: Thomas Richard (TI) <thomas.richard@bootlin.com>
> ---
>  drivers/clk/keystone/sci-clk.c | 44 ++++++++++++++++++++++++++++++++++--------
>  1 file changed, 36 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/clk/keystone/sci-clk.c b/drivers/clk/keystone/sci-clk.c
> index 9d5071223f4c..b090edf5f82e 100644
> --- a/drivers/clk/keystone/sci-clk.c
> +++ b/drivers/clk/keystone/sci-clk.c
> @@ -47,6 +47,8 @@ struct sci_clk_provider {
>   * @node:	 Link for handling clocks probed via DT
>   * @cached_req:	 Cached requested freq for determine rate calls
>   * @cached_res:	 Cached result freq for determine rate calls
> + * @parent_id:	 Parent index for this clock
> + * @rate:	 Clock rate
>   */
>  struct sci_clk {
>  	struct clk_hw hw;
> @@ -58,6 +60,8 @@ struct sci_clk {
>  	struct list_head node;
>  	unsigned long cached_req;
>  	unsigned long cached_res;
> +	u8 parent_id;
> +	unsigned long rate;
>  };
>  
>  #define to_sci_clk(_hw) container_of(_hw, struct sci_clk, hw)
> @@ -150,6 +154,8 @@ static unsigned long sci_clk_recalc_rate(struct clk_hw *hw,
>  		return 0;
>  	}
>  
> +	clk->rate = freq;
> +
>  	return freq;
>  }
>  
> @@ -210,10 +216,15 @@ static int sci_clk_set_rate(struct clk_hw *hw, unsigned long rate,
>  			    unsigned long parent_rate)
>  {
>  	struct sci_clk *clk = to_sci_clk(hw);
> +	int ret;
>  
> -	return clk->provider->ops->set_freq(clk->provider->sci, clk->dev_id,
> -					    clk->clk_id, rate / 10 * 9, rate,
> -					    rate / 10 * 11);
> +	ret = clk->provider->ops->set_freq(clk->provider->sci, clk->dev_id,
> +					   clk->clk_id, rate / 10 * 9, rate,
> +					   rate / 10 * 11);
> +	if (!ret)
> +		clk->rate = rate;
> +
> +	return ret;
>  }
>  
>  /**
> @@ -237,9 +248,9 @@ static u8 sci_clk_get_parent(struct clk_hw *hw)
>  		return 0;

What happens if get_parent() fails during clock registration? Looking at
sci_clk_get_parent(), if the firmware call fails, parent_id will be a
valid value of 0? and in restore, we'd attempt to restore it back? I
think that is wrong.

>  	}
>  
> -	parent_id = parent_id - clk->clk_id - 1;
> +	clk->parent_id = (u8)(parent_id - clk->clk_id - 1);
>  
> -	return (u8)parent_id;
> +	return clk->parent_id;



>  }
>  
>  /**
> @@ -252,12 +263,28 @@ static u8 sci_clk_get_parent(struct clk_hw *hw)
>  static int sci_clk_set_parent(struct clk_hw *hw, u8 index)
>  {
>  	struct sci_clk *clk = to_sci_clk(hw);
> +	int ret;
>  
>  	clk->cached_req = 0;
>  
> -	return clk->provider->ops->set_parent(clk->provider->sci, clk->dev_id,
> -					      clk->clk_id,
> -					      index + 1 + clk->clk_id);
> +	ret = clk->provider->ops->set_parent(clk->provider->sci, clk->dev_id,
> +					     clk->clk_id,
> +					     index + 1 + clk->clk_id);
> +	if (!ret)
> +		clk->parent_id = index;

index of 0 is still a valid value, right? same value clk->parent_id will have
even if ret was 0.

> +
> +	return ret;
> +}
> +
> +static void sci_clk_restore_context(struct clk_hw *hw)
> +{
> +	struct sci_clk *clk = to_sci_clk(hw);
> +
> +	if (clk->num_parents > 1)
> +		sci_clk_set_parent(hw, clk->parent_id);

And we end up attempting invalid parent_id (0) here?

> +
> +	if (clk->rate)
> +		sci_clk_set_rate(hw, clk->rate, 0);
>  }
>  
>  static const struct clk_ops sci_clk_ops = {
> @@ -269,6 +296,7 @@ static const struct clk_ops sci_clk_ops = {
>  	.set_rate = sci_clk_set_rate,
>  	.get_parent = sci_clk_get_parent,
>  	.set_parent = sci_clk_set_parent,
> +	.restore_context = sci_clk_restore_context,
>  };
>  
>  /**
> 
> -- 
> 2.53.0
> 

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D
https://ti.com/opensource