Re: [PATCH v10 18/27] drivers: firmware: psci: Add support for PM domains using genpd

[Lina Iyer]

On Thu, Nov 29 2018 at 10:49 -0700, Ulf Hansson wrote:
> When the hierarchical CPU topology layout is used in DT, we need to setup
> the corresponding PM domain data structures, as to allow a CPU and a group
> of CPUs to be power managed accordingly. Let's enable this by deploying
> support through the genpd interface.
>
> Additionally, when the OS initiated mode is supported by the PSCI FW, let's
> also parse the domain idle states DT bindings as to make genpd responsible
> for the state selection, when the states are compatible with
> "domain-idle-state". Otherwise, when only Platform Coordinated mode is
> supported, we rely solely on the state selection to be managed through the
> regular cpuidle framework.
>
> If the initialization of the PM domain data structures succeeds and the OS
> initiated mode is supported, we try to switch to it. In case it fails,
> let's fall back into a degraded mode, rather than bailing out and returning
> an error code.
>
> Due to that the OS initiated mode may become enabled, we need to adjust to
> maintain backwards compatibility for a kernel started through a kexec call.
> Do this by explicitly switch to Platform Coordinated mode during boot.
>
> To try to initiate the PM domain data structures, the PSCI driver shall
> call the new function, psci_dt_init_pm_domains(). However, this is done
> from following changes.
>
> Cc: Lina Iyer <ilina@xxxxxxxxxxxxxx>
> Co-developed-by: Lina Iyer <lina.iyer@xxxxxxxxxx>
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> ---
>
> Changes in V10:
> 	- Enable the PM domains to be used for both PC and OSI mode.
> 	- Fixup error paths.
> 	- Move the management of kexec started kernels into this patch.
> 	- Rewrite changelog.
>
> ---
> drivers/firmware/psci/Makefile         |   2 +-
> drivers/firmware/psci/psci.c           |   7 +-
> drivers/firmware/psci/psci.h           |   6 +
> drivers/firmware/psci/psci_pm_domain.c | 262 +++++++++++++++++++++++++
> 4 files changed, 275 insertions(+), 2 deletions(-)
> create mode 100644 drivers/firmware/psci/psci_pm_domain.c
>
> diff --git a/drivers/firmware/psci/Makefile b/drivers/firmware/psci/Makefile
> index 1956b882470f..ff300f1fec86 100644
> --- a/drivers/firmware/psci/Makefile
> +++ b/drivers/firmware/psci/Makefile
> @@ -1,4 +1,4 @@
> # SPDX-License-Identifier: GPL-2.0
> #
> -obj-$(CONFIG_ARM_PSCI_FW)	+= psci.o
> +obj-$(CONFIG_ARM_PSCI_FW)	+= psci.o psci_pm_domain.o
> obj-$(CONFIG_ARM_PSCI_CHECKER)	+= psci_checker.o
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 623591b541a4..19af2093151b 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -704,9 +704,14 @@ static int __init psci_1_0_init(struct device_node *np)
> 	if (err)
> 		return err;
>
> -	if (psci_has_osi_support())
> +	if (psci_has_osi_support()) {
> 		pr_info("OSI mode supported.\n");
>
> +		/* Make sure we default to PC mode. */
> +		invoke_psci_fn(PSCI_1_0_FN_SET_SUSPEND_MODE,
> +			       PSCI_1_0_SUSPEND_MODE_PC, 0, 0);
> +	}
> +
> 	return 0;
> }
>
> diff --git a/drivers/firmware/psci/psci.h b/drivers/firmware/psci/psci.h
> index 7d9d38fd57e1..8cf6d7206fab 100644
> --- a/drivers/firmware/psci/psci.h
> +++ b/drivers/firmware/psci/psci.h
> @@ -11,4 +11,10 @@ void psci_set_domain_state(u32 state);
> bool psci_has_osi_support(void);
> int psci_dt_parse_state_node(struct device_node *np, u32 *state);
>
> +#ifdef CONFIG_CPU_IDLE
> +int psci_dt_init_pm_domains(struct device_node *np);
> +#else
> +static inline int psci_dt_init_pm_domains(struct device_node *np) { return 0; }
> +#endif
> +
> #endif /* __PSCI_H */
> diff --git a/drivers/firmware/psci/psci_pm_domain.c b/drivers/firmware/psci/psci_pm_domain.c
> new file mode 100644
> index 000000000000..d0dc38e96f85
> --- /dev/null
> +++ b/drivers/firmware/psci/psci_pm_domain.c
> @@ -0,0 +1,262 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * PM domains for CPUs via genpd - managed by PSCI.
> + *
> + * Copyright (C) 2018 Linaro Ltd.
> + * Author: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> + *
> + */
> +
> +#define pr_fmt(fmt) "psci: " fmt
> +
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/pm_domain.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +
> +#include "psci.h"
> +
> +#ifdef CONFIG_CPU_IDLE
> +
> +struct psci_pd_provider {
> +	struct list_head link;
> +	struct device_node *node;
> +};
> +
> +static LIST_HEAD(psci_pd_providers);
> +static bool osi_mode_enabled;
> +
> +static int psci_pd_power_off(struct generic_pm_domain *pd)
> +{
> +	struct genpd_power_state *state = &pd->states[pd->state_idx];
> +	u32 *pd_state;
> +	u32 composite_pd_state;
> +
> +	/* If we have failed to enable OSI mode, then abort power off. */
> +	if (psci_has_osi_support() && !osi_mode_enabled)
> +		return -EBUSY;
> +
> +	if (!state->data)
> +		return 0;
> +
> +	/* When OSI mode is enabled, set the corresponding domain state. */
> +	pd_state = state->data;
> +	composite_pd_state = *pd_state | psci_get_domain_state();
This should not be needed. The domain_state should be 0x0 being set
after coming out of idle.
> +	psci_set_domain_state(composite_pd_state);
The three lines can be summarized as:
	psci_set_domain_state(*state->data);

Thanks,
Lina