| From: Hans de Goede <hdegoede@redhat.com> |
| Date: Thu, 26 Apr 2018 14:10:23 +0200 |
| Subject: pwm: lpss: platform: Save/restore the ctrl register over a |
| suspend/resume |
| |
| commit 1d375b58c12f08d8570b30b865def4734517f04f upstream. |
| |
| 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. |
| |
| Signed-off-by: Hans de Goede <hdegoede@redhat.com> |
| Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> |
| Signed-off-by: Thierry Reding <thierry.reding@gmail.com> |
| [bwh: Backported to 3.16: |
| - pwm-lpss is a single module, so make the new functions static |
| - Only one PWM per chip is supported; remove the npwm assertion and loops |
| - Adjust filenames, context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| --- a/drivers/pwm/pwm-lpss.c |
| +++ b/drivers/pwm/pwm-lpss.c |
| @@ -39,6 +39,7 @@ struct pwm_lpss_chip { |
| void __iomem *regs; |
| struct clk *clk; |
| unsigned long clk_rate; |
| + u32 saved_ctrl; |
| }; |
| |
| struct pwm_lpss_boardinfo { |
| @@ -177,6 +178,24 @@ static int pwm_lpss_remove(struct pwm_lp |
| return pwmchip_remove(&lpwm->chip); |
| } |
| |
| +static int pwm_lpss_suspend(struct device *dev) |
| +{ |
| + struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev); |
| + |
| + lpwm->saved_ctrl = readl(lpwm->regs + PWM); |
| + |
| + return 0; |
| +} |
| + |
| +static int pwm_lpss_resume(struct device *dev) |
| +{ |
| + struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev); |
| + |
| + writel(lpwm->saved_ctrl, lpwm->regs + PWM); |
| + |
| + return 0; |
| +} |
| + |
| static int pwm_lpss_probe_pci(struct pci_dev *pdev, |
| const struct pci_device_id *id) |
| { |
| @@ -241,6 +260,10 @@ static int pwm_lpss_remove_platform(stru |
| 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", 0 }, |
| { }, |
| @@ -251,6 +274,7 @@ static struct platform_driver pwm_lpss_d |
| .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, |