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

From: Taniya Das
Date: Mon Dec 09 2019 - 23:47:43 EST

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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@xxxxxxxxxxxxx>
---
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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Next message: Daniel Axtens: "[PATCH v2 2/4] kasan: use MAX_PTRS_PER_* for early shadow"
Previous message: Daniel Axtens: "[PATCH v2 1/4] mm: define MAX_PTRS_PER_{PTE,PMD,PUD}"
Next in thread: Brian Masney: "Re: [PATCH 1/7] clk: qcom: add support for setting the duty cycle"
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