Re: [PATCH 1/7] clk: qcom: add support for setting the duty cycle

Taniya Das
2019-12-10T04:47:38Z

Hi Brian,

On 12/5/2019 5:54 AM, Brian Masney wrote:
> Add support for setting the duty cycle via the D register for the
> Qualcomm clocks.
>
> Signed-off-by: Brian Masney <masneyb@onstation.org>
> ---
> A few quirks that were noted when varying the speed of CAMSS_GP1_CLK on
> msm8974 (Nexus 5 phone):
>
> - The mnd_width is set to 8 bits, however the d width is actually 7
> bits, at least for this clock. I'm not sure about the other clocks.
>
> - When the d register has a value less than 17, the following error
> from update_config() is shown: rcg didn't update its configuration.
> So this patch keeps the value of the d register within the range
> [17, 127].
>
> I'm not sure about the relationship of the m, n, and d values,
> especially how the 50% duty cycle is calculated by inverting the n
> value, so that's why I'm saving the duty cycle ratio for
> get_duty_cycle().
>
> drivers/clk/qcom/clk-rcg.h | 4 +++
> drivers/clk/qcom/clk-rcg2.c | 61 +++++++++++++++++++++++++++++++++++--
> 2 files changed, 63 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/qcom/clk-rcg.h b/drivers/clk/qcom/clk-rcg.h
> index 78358b81d249..c3b8732cec8f 100644
> --- a/drivers/clk/qcom/clk-rcg.h
> +++ b/drivers/clk/qcom/clk-rcg.h
> @@ -139,6 +139,8 @@ extern const struct clk_ops clk_dyn_rcg_ops;
> * @freq_tbl: frequency table
> * @clkr: regmap clock handle
> * @cfg_off: defines the cfg register offset from the CMD_RCGR + CFG_REG
> + * @duty_cycle_num: Numerator of the duty cycle ratio
> + * @duty_cycle_den: Denominator of the duty cycle ratio
> */
> struct clk_rcg2 {
> u32 cmd_rcgr;
> @@ -149,6 +151,8 @@ struct clk_rcg2 {
> const struct freq_tbl *freq_tbl;
> struct clk_regmap clkr;
> u8 cfg_off;
> + int duty_cycle_num;
> + int duty_cycle_den;
> };
>
> #define to_clk_rcg2(_hw) container_of(to_clk_regmap(_hw), struct clk_rcg2, clkr)
> diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c
> index 8f4b9bec2956..8d685baefe50 100644
> --- a/drivers/clk/qcom/clk-rcg2.c
> +++ b/drivers/clk/qcom/clk-rcg2.c
> @@ -258,7 +258,11 @@ static int clk_rcg2_determine_floor_rate(struct clk_hw *hw,
> return _freq_tbl_determine_rate(hw, rcg->freq_tbl, req, FLOOR);
> }
>
> -static int __clk_rcg2_configure(struct clk_rcg2 *rcg, const struct freq_tbl *f)
> +static int __clk_rcg2_configure_with_duty_cycle(struct clk_rcg2 *rcg,
> + const struct freq_tbl *f,
> + int d_reg_val,
> + int duty_cycle_num,
> + int duty_cycle_den)
> {
> u32 cfg, mask;
> struct clk_hw *hw = &rcg->clkr.hw;
> @@ -280,9 +284,12 @@ static int __clk_rcg2_configure(struct clk_rcg2 *rcg, const struct freq_tbl *f)
> return ret;
>
> ret = regmap_update_bits(rcg->clkr.regmap,
> - RCG_D_OFFSET(rcg), mask, ~f->n);
> + RCG_D_OFFSET(rcg), mask, d_reg_val);
> if (ret)
> return ret;
> +
> + rcg->duty_cycle_num = duty_cycle_num;
> + rcg->duty_cycle_den = duty_cycle_den;
> }
>
> mask = BIT(rcg->hid_width) - 1;
> @@ -295,6 +302,12 @@ static int __clk_rcg2_configure(struct clk_rcg2 *rcg, const struct freq_tbl *f)
> mask, cfg);
> }
>
> +static int __clk_rcg2_configure(struct clk_rcg2 *rcg, const struct freq_tbl *f)
> +{
> + /* Set a 50% duty cycle */
> + return __clk_rcg2_configure_with_duty_cycle(rcg, f, ~f->n, 1, 2);
> +}
> +
> static int clk_rcg2_configure(struct clk_rcg2 *rcg, const struct freq_tbl *f)
> {
> int ret;
> @@ -353,6 +366,32 @@ static int clk_rcg2_set_floor_rate_and_parent(struct clk_hw *hw,
> return __clk_rcg2_set_rate(hw, rate, FLOOR);
> }
>
> +static int clk_rcg2_get_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
> +{
> + struct clk_rcg2 *rcg = to_clk_rcg2(hw);
> +
> + duty->num = rcg->duty_cycle_num;
> + duty->den = rcg->duty_cycle_den;
> +
> + return 0;
> +}
> +
> +static int clk_rcg2_set_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
> +{
> + struct clk_rcg2 *rcg = to_clk_rcg2(hw);
> + int ret, d_reg_val, mask;
> +
> + mask = BIT(rcg->mnd_width - 1) - 1;
> + d_reg_val = mask - (((mask - 17) * duty->num) / duty->den);
> + ret = __clk_rcg2_configure_with_duty_cycle(rcg, rcg->freq_tbl,
> + d_reg_val, duty->num,
> + duty->den);

The duty-cycle calculation is not accurate.
There is already a plan to submit the duty-cycle changes from my side.
> + if (ret)
> + return ret;
> +
> + return update_config(rcg);
> +}
> +
> const struct clk_ops clk_rcg2_ops = {
> .is_enabled = clk_rcg2_is_enabled,
> .get_parent = clk_rcg2_get_parent,
> @@ -361,6 +400,8 @@ const struct clk_ops clk_rcg2_ops = {
> .determine_rate = clk_rcg2_determine_rate,
> .set_rate = clk_rcg2_set_rate,
> .set_rate_and_parent = clk_rcg2_set_rate_and_parent,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
> EXPORT_SYMBOL_GPL(clk_rcg2_ops);
>
> @@ -372,6 +413,8 @@ const struct clk_ops clk_rcg2_floor_ops = {
> .determine_rate = clk_rcg2_determine_floor_rate,
> .set_rate = clk_rcg2_set_floor_rate,
> .set_rate_and_parent = clk_rcg2_set_floor_rate_and_parent,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
> EXPORT_SYMBOL_GPL(clk_rcg2_floor_ops);
>
> @@ -499,6 +542,8 @@ const struct clk_ops clk_edp_pixel_ops = {
> .set_rate = clk_edp_pixel_set_rate,
> .set_rate_and_parent = clk_edp_pixel_set_rate_and_parent,
> .determine_rate = clk_edp_pixel_determine_rate,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
> EXPORT_SYMBOL_GPL(clk_edp_pixel_ops);
>
> @@ -557,6 +602,8 @@ const struct clk_ops clk_byte_ops = {
> .set_rate = clk_byte_set_rate,
> .set_rate_and_parent = clk_byte_set_rate_and_parent,
> .determine_rate = clk_byte_determine_rate,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
> EXPORT_SYMBOL_GPL(clk_byte_ops);
>
> @@ -627,6 +674,8 @@ const struct clk_ops clk_byte2_ops = {
> .set_rate = clk_byte2_set_rate,
> .set_rate_and_parent = clk_byte2_set_rate_and_parent,
> .determine_rate = clk_byte2_determine_rate,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
> EXPORT_SYMBOL_GPL(clk_byte2_ops);
>
> @@ -717,6 +766,8 @@ const struct clk_ops clk_pixel_ops = {
> .set_rate = clk_pixel_set_rate,
> .set_rate_and_parent = clk_pixel_set_rate_and_parent,
> .determine_rate = clk_pixel_determine_rate,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
> EXPORT_SYMBOL_GPL(clk_pixel_ops);
>
> @@ -804,6 +855,8 @@ const struct clk_ops clk_gfx3d_ops = {
> .set_rate = clk_gfx3d_set_rate,
> .set_rate_and_parent = clk_gfx3d_set_rate_and_parent,
> .determine_rate = clk_gfx3d_determine_rate,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
> EXPORT_SYMBOL_GPL(clk_gfx3d_ops);
>
> @@ -942,6 +995,8 @@ const struct clk_ops clk_rcg2_shared_ops = {
> .determine_rate = clk_rcg2_determine_rate,
> .set_rate = clk_rcg2_shared_set_rate,
> .set_rate_and_parent = clk_rcg2_shared_set_rate_and_parent,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
> EXPORT_SYMBOL_GPL(clk_rcg2_shared_ops);
>
> @@ -1081,6 +1136,8 @@ static const struct clk_ops clk_rcg2_dfs_ops = {
> .get_parent = clk_rcg2_get_parent,
> .determine_rate = clk_rcg2_dfs_determine_rate,
> .recalc_rate = clk_rcg2_dfs_recalc_rate,
> + .get_duty_cycle = clk_rcg2_get_duty_cycle,
> + .set_duty_cycle = clk_rcg2_set_duty_cycle,
> };
>

Why do you want to support duty-cycle for other RCGs when you are
specifically want it for GP clocks only.
The DFS can never handle duty-cycle set/get.

> static int clk_rcg2_enable_dfs(const struct clk_rcg_dfs_data *data,
>

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