On Thursday, April 26, 2018 2:10:23 PM CEST Hans de Goede wrote:
> On some devices the contents of the ctrl register get lost over a
> suspend/resume and the PWM comes back up disabled after the resume.
>
> This is seen on some Bay Trail devices with the PWM in ACPI enumerated
> mode, so it shows up as a platform device instead of a PCI device.
>
> If we still think it is enabled and then try to change the duty-cycle
> after this, we end up with a "PWM_SW_UPDATE was not cleared" error and
> the PWM is stuck in that state from then on.
>
> This commit adds suspend and resume pm callbacks to the pwm-lpss-platform
> code, which save/restore the ctrl register over a suspend/resume, fixing
> this.
>
> Note that:
>
> 1) There is no need to do this over a runtime suspend, since we
> only runtime suspend when disabled and then we properly set the enable
> bit and reprogram the timings when we re-enable the PWM.
>
> 2) This may be happening on more systems then we realize, but has been
> covered up sofar by a bug in the acpi-lpss.c code which was save/restoring
> the regular device registers instead of the lpss private registers due to
> lpss_device_desc.prv_offset not being set. This is fixed by a later patch
> in this series.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Andy, Thierry, any comments or concerns regarding this series?
> ---
> Changes in v2:
> -Add Cc: stable@xxxxxxxxxxxxxxx to make sure this goes into stable
> together with "ACPI / LPSS: Add missing prv_offset setting for byt/cht
> PWM devices" which depends on this
> ---
> drivers/pwm/pwm-lpss-platform.c | 5 +++++
> drivers/pwm/pwm-lpss.c | 30 ++++++++++++++++++++++++++++++
> drivers/pwm/pwm-lpss.h | 2 ++
> 3 files changed, 37 insertions(+)
>
> diff --git a/drivers/pwm/pwm-lpss-platform.c b/drivers/pwm/pwm-lpss-platform.c
> index 5d6ed1507d29..5561b9e190f8 100644
> --- a/drivers/pwm/pwm-lpss-platform.c
> +++ b/drivers/pwm/pwm-lpss-platform.c
> @@ -74,6 +74,10 @@ static int pwm_lpss_remove_platform(struct platform_device *pdev)
> return pwm_lpss_remove(lpwm);
> }
>
> +static SIMPLE_DEV_PM_OPS(pwm_lpss_platform_pm_ops,
> + pwm_lpss_suspend,
> + pwm_lpss_resume);
> +
> static const struct acpi_device_id pwm_lpss_acpi_match[] = {
> { "80860F09", (unsigned long)&pwm_lpss_byt_info },
> { "80862288", (unsigned long)&pwm_lpss_bsw_info },
> @@ -86,6 +90,7 @@ static struct platform_driver pwm_lpss_driver_platform = {
> .driver = {
> .name = "pwm-lpss",
> .acpi_match_table = pwm_lpss_acpi_match,
> + .pm = &pwm_lpss_platform_pm_ops,
> },
> .probe = pwm_lpss_probe_platform,
> .remove = pwm_lpss_remove_platform,
> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
> index 8db0d40ccacd..4721a264bac2 100644
> --- a/drivers/pwm/pwm-lpss.c
> +++ b/drivers/pwm/pwm-lpss.c
> @@ -32,10 +32,13 @@
> /* Size of each PWM register space if multiple */
> #define PWM_SIZE 0x400
>
> +#define MAX_PWMS 4
> +
> struct pwm_lpss_chip {
> struct pwm_chip chip;
> void __iomem *regs;
> const struct pwm_lpss_boardinfo *info;
> + u32 saved_ctrl[MAX_PWMS];
> };
>
> static inline struct pwm_lpss_chip *to_lpwm(struct pwm_chip *chip)
> @@ -177,6 +180,9 @@ struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
> unsigned long c;
> int ret;
>
> + if (WARN_ON(info->npwm > MAX_PWMS))
> + return ERR_PTR(-ENODEV);
> +
> lpwm = devm_kzalloc(dev, sizeof(*lpwm), GFP_KERNEL);
> if (!lpwm)
> return ERR_PTR(-ENOMEM);
> @@ -212,6 +218,30 @@ int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
> }
> EXPORT_SYMBOL_GPL(pwm_lpss_remove);
>
> +int pwm_lpss_suspend(struct device *dev)
> +{
> + struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
> + int i;
> +
> + for (i = 0; i < lpwm->info->npwm; i++)
> + lpwm->saved_ctrl[i] = readl(lpwm->regs + i * PWM_SIZE + PWM);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(pwm_lpss_suspend);
> +
> +int pwm_lpss_resume(struct device *dev)
> +{
> + struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
> + int i;
> +
> + for (i = 0; i < lpwm->info->npwm; i++)
> + writel(lpwm->saved_ctrl[i], lpwm->regs + i * PWM_SIZE + PWM);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(pwm_lpss_resume);
> +
> MODULE_DESCRIPTION("PWM driver for Intel LPSS");
> MODULE_AUTHOR("Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>");
> MODULE_LICENSE("GPL v2");
> diff --git a/drivers/pwm/pwm-lpss.h b/drivers/pwm/pwm-lpss.h
> index 98306bb02cfe..7a4238ad1fcb 100644
> --- a/drivers/pwm/pwm-lpss.h
> +++ b/drivers/pwm/pwm-lpss.h
> @@ -28,5 +28,7 @@ struct pwm_lpss_boardinfo {
> struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
> const struct pwm_lpss_boardinfo *info);
> int pwm_lpss_remove(struct pwm_lpss_chip *lpwm);
> +int pwm_lpss_suspend(struct device *dev);
> +int pwm_lpss_resume(struct device *dev);
>
> #endif /* __PWM_LPSS_H */
>
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
