Re: [RFC PATCH 1/5] clk: qcom: regmap-mux: add pipe clk implementation

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Sat 12 Mar 18:08 CST 2022, Dmitry Baryshkov wrote:

> PCIe PIPE clk (and some other clocks) must be parked to the "safe"

How about changing this to:

"On recent Qualcomm platforms the QMP PIPE clocks feed into a set of
muxes which must be parked..."

To cover the fact that the design changed recently and that it relates
to (at least) USB as well.

> source (bi_tcxo) when corresponding GDSC is turned off and on again.
> Currently this is handcoded in the PCIe driver, reparenting the
> gcc_pipe_N_clk_src clock. However the same code sequence should be
> applied in the pcie-qcom-ep, USB3 and UFS drivers.
> 
> Rather than copying this sequence over and over again, follow the
> example of clk_rcg2_shared_ops and implement this parking in the
> enable() and disable() clock operations. As we are changing the parent
> behind the back of the clock framework, also implement custom
> set_parent() and get_parent() operations behaving accroding to the clock
> framework expectations (cache the new parent if the clock is in disabled
> state, return cached parent).
> 

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Regards,
Bjorn

> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  drivers/clk/qcom/clk-regmap-mux.c | 70 +++++++++++++++++++++++++++++++
>  drivers/clk/qcom/clk-regmap-mux.h |  3 ++
>  2 files changed, 73 insertions(+)
> 
> diff --git a/drivers/clk/qcom/clk-regmap-mux.c b/drivers/clk/qcom/clk-regmap-mux.c
> index 45d9cca28064..024412b070c5 100644
> --- a/drivers/clk/qcom/clk-regmap-mux.c
> +++ b/drivers/clk/qcom/clk-regmap-mux.c
> @@ -49,9 +49,79 @@ static int mux_set_parent(struct clk_hw *hw, u8 index)
>  	return regmap_update_bits(clkr->regmap, mux->reg, mask, val);
>  }
>  
> +static u8 mux_safe_get_parent(struct clk_hw *hw)
> +{
> +	struct clk_regmap_mux *mux = to_clk_regmap_mux(hw);
> +	unsigned int val;
> +
> +	if (clk_hw_is_enabled(hw))
> +		return mux_get_parent(hw);
> +
> +	val = mux->stored_parent;
> +
> +	if (mux->parent_map)
> +		return qcom_find_cfg_index(hw, mux->parent_map, val);
> +
> +	return val;
> +}
> +
> +static int mux_safe_set_parent(struct clk_hw *hw, u8 index)
> +{
> +	struct clk_regmap_mux *mux = to_clk_regmap_mux(hw);
> +
> +	if (clk_hw_is_enabled(hw))
> +		return mux_set_parent(hw, index);
> +
> +	if (mux->parent_map)
> +		index = mux->parent_map[index].cfg;
> +
> +	mux->stored_parent = index;
> +
> +	return 0;
> +}
> +
> +static void mux_safe_disable(struct clk_hw *hw)
> +{
> +	struct clk_regmap_mux *mux = to_clk_regmap_mux(hw);
> +	struct clk_regmap *clkr = to_clk_regmap(hw);
> +	unsigned int mask = GENMASK(mux->width + mux->shift - 1, mux->shift);
> +	unsigned int val;
> +
> +	regmap_read(clkr->regmap, mux->reg, &val);
> +
> +	mux->stored_parent = (val & mask) >> mux->shift;
> +
> +	val = mux->safe_src_index;
> +	val <<= mux->shift;
> +
> +	regmap_update_bits(clkr->regmap, mux->reg, mask, val);
> +}
> +
> +static int mux_safe_enable(struct clk_hw *hw)
> +{
> +	struct clk_regmap_mux *mux = to_clk_regmap_mux(hw);
> +	struct clk_regmap *clkr = to_clk_regmap(hw);
> +	unsigned int mask = GENMASK(mux->width + mux->shift - 1, mux->shift);
> +	unsigned int val;
> +
> +	val = mux->stored_parent;
> +	val <<= mux->shift;
> +
> +	return regmap_update_bits(clkr->regmap, mux->reg, mask, val);
> +}
> +
>  const struct clk_ops clk_regmap_mux_closest_ops = {
>  	.get_parent = mux_get_parent,
>  	.set_parent = mux_set_parent,
>  	.determine_rate = __clk_mux_determine_rate_closest,
>  };
>  EXPORT_SYMBOL_GPL(clk_regmap_mux_closest_ops);
> +
> +const struct clk_ops clk_regmap_mux_safe_ops = {
> +	.enable = mux_safe_enable,
> +	.disable = mux_safe_disable,
> +	.get_parent = mux_safe_get_parent,
> +	.set_parent = mux_safe_set_parent,
> +	.determine_rate = __clk_mux_determine_rate_closest,
> +};
> +EXPORT_SYMBOL_GPL(clk_regmap_mux_safe_ops);
> diff --git a/drivers/clk/qcom/clk-regmap-mux.h b/drivers/clk/qcom/clk-regmap-mux.h
> index db6f4cdd9586..ab8ab25d79bd 100644
> --- a/drivers/clk/qcom/clk-regmap-mux.h
> +++ b/drivers/clk/qcom/clk-regmap-mux.h
> @@ -14,10 +14,13 @@ struct clk_regmap_mux {
>  	u32			reg;
>  	u32			shift;
>  	u32			width;
> +	u8			safe_src_index;
> +	u8			stored_parent;
>  	const struct parent_map	*parent_map;
>  	struct clk_regmap	clkr;
>  };
>  
>  extern const struct clk_ops clk_regmap_mux_closest_ops;
> +extern const struct clk_ops clk_regmap_mux_safe_ops;
>  
>  #endif
> -- 
> 2.34.1
>