From: "Heiko Stübner" <heiko@sntech.de>
To: thierry.reding@gmail.com, u.kleine-koenig@pengutronix.de,
lee.jones@linaro.org, linux-pwm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-rockchip@lists.infradead.org,
Simon South <simon@simonsouth.net>
Cc: Simon South <simon@simonsouth.net>
Subject: Re: [PATCH v2] pwm: rockchip: Keep enabled PWMs running while probing
Date: Wed, 23 Sep 2020 12:49:01 +0200 [thread overview]
Message-ID: <8127994.CrzmY9MQ1E@diego> (raw)
In-Reply-To: <20200919193306.1023-1-simon@simonsouth.net>
Am Samstag, 19. September 2020, 21:33:06 CEST schrieb Simon South:
> 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.
>
> Fixes: cfc4c189bc70 ("pwm: Read initial hardware state at request time")
> Signed-off-by: Simon South <simon@simonsouth.net>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> ---
> 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;
>
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next prev parent reply other threads:[~2020-09-23 10:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-19 19:33 [PATCH v2] pwm: rockchip: Keep enabled PWMs running while probing Simon South
2020-09-21 8:01 ` Uwe Kleine-König
2020-09-23 10:49 ` Heiko Stübner [this message]
2020-09-23 11:41 ` Thierry Reding
2020-11-21 1:09 ` Trent Piepho
2020-11-30 0:36 ` Simon South
2020-11-30 0:44 ` [PATCH] pwm: rockchip: Eliminate potential race condition when probing Simon South
2020-12-10 17:48 ` Thierry Reding
2020-12-10 21:00 ` Trent Piepho
2020-12-11 10:44 ` Robin Murphy
2020-12-19 20:32 ` Simon South
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