All of lore.kernel.org
 help / color / mirror / Atom feed
From: Simon South <simon@simonsouth.net>
To: heiko@sntech.de, linux-rockchip@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org
Cc: Simon South <simon@simonsouth.net>
Subject: [PATCH] pwm: rockchip: Keep enabled PWMs running while probing
Date: Fri, 18 Sep 2020 16:48:25 -0400	[thread overview]
Message-ID: <20200918204825.4744-1-simon@simonsouth.net> (raw)

Following commit cfc4c189bc70 ("pwm: Read initial hardware state at
request time") the Rockchip PWM driver can no longer assume a device's
pwm_state structure has been populated after a call to pwmchip_add().
Consequently, the test in rockchip_pwm_probe() intended to prevent the
driver from stopping PWM devices already enabled by the bootloader no
longer functions reliably and this can lead to the kernel hanging
during startup, particularly on devices like the Pinebook Pro that use
a PWM-controlled backlight for their display.

Avoid this by querying the device directly at probe time to determine
whether or not it is enabled.

Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index eb8c9cb645a6..098e94335cb5 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -288,6 +288,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 	const struct of_device_id *id;
 	struct rockchip_pwm_chip *pc;
 	struct resource *r;
+	u32 enable_conf, ctrl;
 	int ret, count;
 
 	id = of_match_device(rockchip_pwm_dt_ids, &pdev->dev);
@@ -362,7 +363,9 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 	}
 
 	/* Keep the PWM clk enabled if the PWM appears to be up and running. */
-	if (!pwm_is_enabled(pc->chip.pwms))
+	enable_conf = pc->data->enable_conf;
+	ctrl = readl_relaxed(pc->base + pc->data->regs.ctrl);
+	if ((ctrl & enable_conf) != enable_conf)
 		clk_disable(pc->clk);
 
 	return 0;
-- 
2.28.0


_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

WARNING: multiple messages have this Message-ID (diff)
From: Simon South <simon@simonsouth.net>
To: heiko@sntech.de, linux-rockchip@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org
Cc: Simon South <simon@simonsouth.net>
Subject: [PATCH] pwm: rockchip: Keep enabled PWMs running while probing
Date: Fri, 18 Sep 2020 16:48:25 -0400	[thread overview]
Message-ID: <20200918204825.4744-1-simon@simonsouth.net> (raw)

Following commit cfc4c189bc70 ("pwm: Read initial hardware state at
request time") the Rockchip PWM driver can no longer assume a device's
pwm_state structure has been populated after a call to pwmchip_add().
Consequently, the test in rockchip_pwm_probe() intended to prevent the
driver from stopping PWM devices already enabled by the bootloader no
longer functions reliably and this can lead to the kernel hanging
during startup, particularly on devices like the Pinebook Pro that use
a PWM-controlled backlight for their display.

Avoid this by querying the device directly at probe time to determine
whether or not it is enabled.

Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index eb8c9cb645a6..098e94335cb5 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -288,6 +288,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 	const struct of_device_id *id;
 	struct rockchip_pwm_chip *pc;
 	struct resource *r;
+	u32 enable_conf, ctrl;
 	int ret, count;
 
 	id = of_match_device(rockchip_pwm_dt_ids, &pdev->dev);
@@ -362,7 +363,9 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 	}
 
 	/* Keep the PWM clk enabled if the PWM appears to be up and running. */
-	if (!pwm_is_enabled(pc->chip.pwms))
+	enable_conf = pc->data->enable_conf;
+	ctrl = readl_relaxed(pc->base + pc->data->regs.ctrl);
+	if ((ctrl & enable_conf) != enable_conf)
 		clk_disable(pc->clk);
 
 	return 0;
-- 
2.28.0


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

             reply	other threads:[~2020-09-18 20:49 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-18 20:48 Simon South [this message]
2020-09-18 20:48 ` [PATCH] pwm: rockchip: Keep enabled PWMs running while probing Simon South
2020-09-19  8:35 ` Heiko Stübner
2020-09-19  8:35   ` Heiko Stübner

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200918204825.4744-1-simon@simonsouth.net \
    --to=simon@simonsouth.net \
    --cc=heiko@sntech.de \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-rockchip@lists.infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.