linux-kernel - [PATCH RESEND for 5.10] pwm: sl28cpld: fix getting driver data in pwm callbacks

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Date:   Thu,  3 Dec 2020 09:41:42 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>, kernel@...gutronix.de,
        Michael Walle <michael@...le.cc>
Subject: [PATCH RESEND for 5.10] pwm: sl28cpld: fix getting driver data in pwm callbacks

Currently .get_state() and .apply() use dev_get_drvdata() on the struct
device related to the pwm chip. This only works after .probe() called
platform_set_drvdata() which in this driver happens only after
pwmchip_add() and so comes possibly too late.

Instead of setting the driver data earlier use the traditional
container_of approach as this way the driver data is conceptually and
computational nearer.

Fixes: 9db33d221efc ("pwm: Add support for sl28cpld PWM controller")
Tested-by: Michael Walle <michael@...le.cc>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
Hello Linus,

Thierry (who usually sends PWM patches to you) didn't react to this
patch sent to the pwm Mailinglist last week
(https://lore.kernel.org/r/20201124212432.3117322-1-u.kleine-koenig@pengutronix.de)
yet.

Given v5.10 isn't far away any more and I don't know when Thierry will
take a look and act, I'm sending this directly to you. The affected
driver was new in 5.10-rc1 and at least once the unpatched driver
created an oops:

	https://lavalab.kontron.com/scheduler/job/108#L950

Michael Walle who tested this patch is the original author of the
driver. IMHO it would be good to have this fixed before 5.10.

If you prefer a pull request, I can setup something (but I don't have
access to Thierry's tree, so it will be for a repository that's new to
you).

Best regards
Uwe

 drivers/pwm/pwm-sl28cpld.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/pwm-sl28cpld.c b/drivers/pwm/pwm-sl28cpld.c
index 5046b6b7fd35..b4c651fc749c 100644
--- a/drivers/pwm/pwm-sl28cpld.c
+++ b/drivers/pwm/pwm-sl28cpld.c
@@ -84,12 +84,14 @@ struct sl28cpld_pwm {
 	struct regmap *regmap;
 	u32 offset;
 };
+#define sl28cpld_pwm_from_chip(_chip) \
+	container_of(_chip, struct sl28cpld_pwm, pwm_chip)

 static void sl28cpld_pwm_get_state(struct pwm_chip *chip,
 				   struct pwm_device *pwm,
 				   struct pwm_state *state)
 {
-	struct sl28cpld_pwm *priv = dev_get_drvdata(chip->dev);
+	struct sl28cpld_pwm *priv = sl28cpld_pwm_from_chip(chip);
 	unsigned int reg;
 	int prescaler;

@@ -118,7 +120,7 @@ static void sl28cpld_pwm_get_state(struct pwm_chip *chip,
 static int sl28cpld_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			      const struct pwm_state *state)
 {
-	struct sl28cpld_pwm *priv = dev_get_drvdata(chip->dev);
+	struct sl28cpld_pwm *priv = sl28cpld_pwm_from_chip(chip);
 	unsigned int cycle, prescaler;
 	bool write_duty_cycle_first;
 	int ret;
-- 
2.29.2