[PATCH v5 25/46] pwm: sti: avoid glitches on already running PWMs

Boris Brezillon
2016-03-30T20:03:48Z

The current logic will disable the PWM clk even if a PWM was left
enabled by the bootloader (because it's controlling a critical device
like a regulator for example).
Keep the PWM clk enabled if at least one PWM is enabled to avoid any
glitches.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
drivers/pwm/pwm-sti.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/pwm-sti.c b/drivers/pwm/pwm-sti.c
index 0fbca94..bea1d17 100644
--- a/drivers/pwm/pwm-sti.c
+++ b/drivers/pwm/pwm-sti.c
@@ -343,7 +343,7 @@ static int sti_pwm_probe(struct platform_device *pdev)
struct sti_pwm_compat_data *cdata;
struct sti_pwm_chip *pc;
struct resource *res;
- int ret;
+ int i, ret;

pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
if (!pc)
@@ -394,7 +394,7 @@ static int sti_pwm_probe(struct platform_device *pdev)
return -EINVAL;
}

- ret = clk_prepare(pc->clk);
+ ret = clk_prepare_enable(pc->clk);
if (ret) {
dev_err(dev, "failed to prepare clock\n");
return ret;
@@ -412,6 +412,19 @@ static int sti_pwm_probe(struct platform_device *pdev)
return ret;
}

+ /*
+ * Keep the PWM clk enabled if some PWMs appear to be up and
+ * running.
+ */
+ for (i = 0; i < pc->chip.npwm; i++) {
+ struct pwm_state pstate;
+
+ pwm_get_state(&pc->chip.pwms[i], &pstate);
+ if (pstate.enabled)
+ clk_enable(pc->clk);
+ }
+ clk_disable(pc->clk);
+
platform_set_drvdata(pdev, pc);

return 0;
--
2.5.0