[linux-sunxi] [PATCH 3/5] pwm: sun4i: Introduce (optional) reset support

[Andre Przywara]

While the PWM IP in the Allwinner H6 SoC is fully compatible to those
used in older SoCs (H3, A64), it features a dedicated reset line which
needs to be de-asserted.
Add support for an optional "resets" DT property in our pwm-sun4i probe
routine, and assert and de-assert the reset line, where needed.
This allows to enable PWM support on the H6.

Signed-off-by: Andre Przywara <andre.przyw...@arm.com>
---
 drivers/pwm/pwm-sun4i.c | 34 +++++++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 078172dee462..4eefb27fe80b 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -17,6 +17,7 @@
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
+#include <linux/reset.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/time.h>
@@ -79,6 +80,7 @@ struct sun4i_pwm_data {
 struct sun4i_pwm_chip {
        struct pwm_chip chip;
        struct clk *clk;
+       struct reset_control *reset;
        void __iomem *base;
        spinlock_t ctrl_lock;
        const struct sun4i_pwm_data *data;
@@ -206,7 +208,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct 
pwm_device *pwm,
        struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
        struct pwm_state cstate;
        u32 ctrl;
-       int ret;
+       int ret = 0;
        unsigned int delay_us;
        unsigned long now;
 
@@ -218,6 +220,18 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct 
pwm_device *pwm,
                        dev_err(chip->dev, "failed to enable PWM clock\n");
                        return ret;
                }
+
+               /* Deassert reset if we have a reset control */
+               if (sun4i_pwm->reset) {
+                       ret = reset_control_deassert(sun4i_pwm->reset);
+                       if (ret) {
+                               dev_err(chip->dev,
+                                       "Cannot deassert reset control\n");
+                               clk_disable_unprepare(sun4i_pwm->clk);
+
+                               return ret;
+                       }
+               }
        }
 
        spin_lock(&sun4i_pwm->ctrl_lock);
@@ -234,7 +248,8 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct 
pwm_device *pwm,
                        dev_err(chip->dev, "period exceeds the maximum 
value\n");
                        spin_unlock(&sun4i_pwm->ctrl_lock);
                        if (!cstate.enabled)
-                               clk_disable_unprepare(sun4i_pwm->clk);
+                               goto out_disable;
+
                        return ret;
                }
 
@@ -274,10 +289,8 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct 
pwm_device *pwm,
        if (state->enabled)
                return 0;
 
-       if (!sun4i_pwm->needs_delay[pwm->hwpwm]) {
-               clk_disable_unprepare(sun4i_pwm->clk);
-               return 0;
-       }
+       if (!sun4i_pwm->needs_delay[pwm->hwpwm])
+               goto out_disable;
 
        /* We need a full period to elapse before disabling the channel. */
        now = jiffies;
@@ -299,9 +312,12 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct 
pwm_device *pwm,
        sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
        spin_unlock(&sun4i_pwm->ctrl_lock);
 
+out_disable:
        clk_disable_unprepare(sun4i_pwm->clk);
+       if (sun4i_pwm->reset)
+               reset_control_assert(sun4i_pwm->reset);
 
-       return 0;
+       return ret;
 }
 
 static const struct pwm_ops sun4i_pwm_ops = {
@@ -370,6 +386,10 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
        if (IS_ERR(pwm->clk))
                return PTR_ERR(pwm->clk);
 
+       pwm->reset = devm_reset_control_get_optional(&pdev->dev, NULL);
+       if (IS_ERR(pwm->reset))
+               return PTR_ERR(pwm->reset);
+
        pwm->chip.dev = &pdev->dev;
        pwm->chip.ops = &sun4i_pwm_ops;
        pwm->chip.base = -1;
-- 
2.14.1

-- 
You received this message because you are subscribed to the Google Groups 
"linux-sunxi" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to linux-sunxi+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.