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

From: Lina Iyer <[email-masked]>
Date: Mon, 3 Dec 2018 09:37:17 -0700

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 <[email-masked]>
>Co-developed-by: Lina Iyer <[email-masked]>
>Signed-off-by: Ulf Hansson <[email-masked]>
>---
>
>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 <[email-masked]>
>+ *
>+ */
>+
>+#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

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