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From 1be6854b63eac6438f5ac5f359ce8bbfd16a3693 Mon Sep 17 00:00:00 2001 |
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From: Thierry Reding <treding@nvidia.com> |
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Date: Fri, 21 Sep 2018 12:10:48 +0200 |
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Subject: [PATCH 013/145] hwmon: (pwm-fan) Set fan speed to 0 on suspend |
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|
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[ Upstream commit 95dcd64bc5a27080beaa344edfe5bdcca3d2e7dc ] |
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|
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Technically this is not required because disabling the PWM should be |
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enough. However, when support for atomic operations was implemented in |
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the PWM subsystem, only actual changes to the PWM channel are applied |
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during pwm_config(), which means that during after resume from suspend |
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the old settings won't be applied. |
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|
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One possible solution is for the PWM driver to implement its own PM |
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operations such that settings from before suspend get applied on resume. |
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This has the disadvantage of completely ignoring any particular ordering |
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requirements that PWM user drivers might have, so it is best to leave it |
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up to the user drivers to apply the settings that they want at the |
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appropriate time. |
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|
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Another way to solve this would be to read back the current state of the |
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PWM at the time of resume. That way, in case the configuration was lost |
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during suspend, applying the old settings in PWM user drivers would |
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actually get them applied because they differ from the current settings. |
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However, not all PWM drivers support reading the hardware state, and not |
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all hardware may support it. |
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|
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The best workaround at this point seems to be to let PWM user drivers |
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tell the PWM subsystem that the PWM is turned off by, in addition to |
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disabling it, also setting the duty cycle to 0. This causes the resume |
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operation to apply a configuration that is different from the current |
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configuration, resulting in the proper state from before suspend getting |
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restored. |
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|
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Signed-off-by: Thierry Reding <treding@nvidia.com> |
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Signed-off-by: Guenter Roeck <linux@roeck-us.net> |
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Signed-off-by: Sasha Levin <sashal@kernel.org> |
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--- |
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drivers/hwmon/pwm-fan.c | 12 +++++++++++- |
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1 file changed, 11 insertions(+), 1 deletion(-) |
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|
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diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c |
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index 7838af58f92d..9d611dd268e1 100644 |
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--- a/drivers/hwmon/pwm-fan.c |
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+++ b/drivers/hwmon/pwm-fan.c |
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@@ -290,9 +290,19 @@ static int pwm_fan_remove(struct platform_device *pdev) |
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static int pwm_fan_suspend(struct device *dev) |
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{ |
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struct pwm_fan_ctx *ctx = dev_get_drvdata(dev); |
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+ struct pwm_args args; |
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+ int ret; |
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+ |
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+ pwm_get_args(ctx->pwm, &args); |
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+ |
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+ if (ctx->pwm_value) { |
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+ ret = pwm_config(ctx->pwm, 0, args.period); |
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+ if (ret < 0) |
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+ return ret; |
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|
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- if (ctx->pwm_value) |
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pwm_disable(ctx->pwm); |
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+ } |
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+ |
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return 0; |
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} |
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|
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-- |
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2.19.1 |
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