Re: [PATCH v5 2/2] platform/x86:intel/pmc: Enable the ACPI PM Timer to be turned off when suspended

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Mon, 12 Aug 2024, Marek Maslanka wrote:

> Allow to disable ACPI PM Timer on suspend and enable on resume. A
> disabled timer helps optimise power consumption when the system is
> suspended. On resume the timer is only reactivated if it was activated
> prior to suspend, so unless the ACPI PM timer is enabled in the BIOS,
> this won't change anything.
> 
> The ACPI PM timer is used by Intel's iTCO/wdat_wdt watchdog to drive the
> watchdog, so it doesn't need to run during suspend.
> 
> Signed-off-by: Marek Maslanka <mmaslanka@google.com>
> 
> ---
> Changes in v5:
> - Use renamed acpi_pmtmr_register_suspend_resume_callback instead of
>   acpi_pm_register_suspend_resume_callback
> - Link to v4: https://lore.kernel.org/lkml/20240809131343.1173369-2-mmaslanka@google.com/
> ---
> ---
>  drivers/platform/x86/intel/pmc/adl.c  |  2 ++
>  drivers/platform/x86/intel/pmc/cnp.c  |  2 ++
>  drivers/platform/x86/intel/pmc/core.c | 49 +++++++++++++++++++++++++++
>  drivers/platform/x86/intel/pmc/core.h |  8 +++++
>  drivers/platform/x86/intel/pmc/icl.c  |  2 ++
>  drivers/platform/x86/intel/pmc/mtl.c  |  2 ++
>  drivers/platform/x86/intel/pmc/spt.c  |  2 ++
>  drivers/platform/x86/intel/pmc/tgl.c  |  2 ++
>  8 files changed, 69 insertions(+)
> 
> diff --git a/drivers/platform/x86/intel/pmc/adl.c b/drivers/platform/x86/intel/pmc/adl.c
> index e7878558fd909..9d9c07f44ff61 100644
> --- a/drivers/platform/x86/intel/pmc/adl.c
> +++ b/drivers/platform/x86/intel/pmc/adl.c
> @@ -295,6 +295,8 @@ const struct pmc_reg_map adl_reg_map = {
>  	.ppfear_buckets = CNP_PPFEAR_NUM_ENTRIES,
>  	.pm_cfg_offset = CNP_PMC_PM_CFG_OFFSET,
>  	.pm_read_disable_bit = CNP_PMC_READ_DISABLE_BIT,
> +	.acpi_pm_tmr_ctl_offset = SPT_PMC_ACPI_PM_TMR_CTL_OFFSET,
> +	.acpi_pm_tmr_disable_bit = SPT_PMC_BIT_ACPI_PM_TMR_DISABLE,
>  	.ltr_ignore_max = ADL_NUM_IP_IGN_ALLOWED,
>  	.lpm_num_modes = ADL_LPM_NUM_MODES,
>  	.lpm_num_maps = ADL_LPM_NUM_MAPS,
> diff --git a/drivers/platform/x86/intel/pmc/cnp.c b/drivers/platform/x86/intel/pmc/cnp.c
> index dd72974bf71e2..513c02670c5aa 100644
> --- a/drivers/platform/x86/intel/pmc/cnp.c
> +++ b/drivers/platform/x86/intel/pmc/cnp.c
> @@ -200,6 +200,8 @@ const struct pmc_reg_map cnp_reg_map = {
>  	.ppfear_buckets = CNP_PPFEAR_NUM_ENTRIES,
>  	.pm_cfg_offset = CNP_PMC_PM_CFG_OFFSET,
>  	.pm_read_disable_bit = CNP_PMC_READ_DISABLE_BIT,
> +	.acpi_pm_tmr_ctl_offset = SPT_PMC_ACPI_PM_TMR_CTL_OFFSET,
> +	.acpi_pm_tmr_disable_bit = SPT_PMC_BIT_ACPI_PM_TMR_DISABLE,
>  	.ltr_ignore_max = CNP_NUM_IP_IGN_ALLOWED,
>  	.etr3_offset = ETR3_OFFSET,
>  };
> diff --git a/drivers/platform/x86/intel/pmc/core.c b/drivers/platform/x86/intel/pmc/core.c
> index 10c96c1a850af..d65e3e77ec2ca 100644
> --- a/drivers/platform/x86/intel/pmc/core.c
> +++ b/drivers/platform/x86/intel/pmc/core.c
> @@ -11,6 +11,7 @@
>  
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>  
> +#include <linux/acpi_pmtmr.h>
>  #include <linux/bitfield.h>
>  #include <linux/debugfs.h>
>  #include <linux/delay.h>
> @@ -1171,6 +1172,42 @@ static bool pmc_core_is_pson_residency_enabled(struct pmc_dev *pmcdev)
>  	return val == 1;
>  }
>  
> +/**
> + * Enable or disable ACPI PM Timer
> + *
> + * This function is intended to be a callback for ACPI PM suspend/resume event.
> + * The ACPI PM Timer is enabled on resume only if it was enabled during suspend.
> + */
> +static void pmc_core_acpi_pm_timer_suspend_resume(void *data, bool suspend)
> +{
> +	struct pmc_dev *pmcdev = data;
> +	struct pmc *pmc = pmcdev->pmcs[PMC_IDX_MAIN];
> +	const struct pmc_reg_map *map = pmc->map;
> +	bool enabled;
> +	u32 reg;
> +
> +	if (!map->acpi_pm_tmr_ctl_offset)
> +		return;
> +
> +	mutex_lock(&pmcdev->lock);
> +
> +	if (!suspend && !pmcdev->enable_acpi_pm_timer_on_resume) {
> +		mutex_unlock(&pmcdev->lock);

Use guard() in this function so you don't need to manually unlock.

-- 
 i.


> +		return;
> +	}
> +
> +	reg = pmc_core_reg_read(pmc, map->acpi_pm_tmr_ctl_offset);
> +	enabled = !(reg & map->acpi_pm_tmr_disable_bit);
> +	if (suspend)
> +		reg |= map->acpi_pm_tmr_disable_bit;
> +	else
> +		reg &= ~map->acpi_pm_tmr_disable_bit;
> +	pmc_core_reg_write(pmc, map->acpi_pm_tmr_ctl_offset, reg);
> +
> +	pmcdev->enable_acpi_pm_timer_on_resume = suspend && enabled;
> +
> +	mutex_unlock(&pmcdev->lock);
> +}