On Thu, 19 Dec 2019 at 15:34, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
>
> On Wed, Dec 11, 2019 at 04:43:42PM +0100, Ulf Hansson wrote:
> > When the hierarchical CPU topology layout is used in DT and the PSCI OSI
> > mode is supported by the PSCI FW, let's initialize a corresponding PM
> > domain topology by using genpd. This enables a CPU and a group of CPUs,
> > when attached to the topology, to be power-managed accordingly.
> >
> > To trigger the attempt to initialize the genpd data structures let's use a
> > subsys_initcall, which should be early enough to allow CPUs, but also other
> > devices to be attached.
> >
> > The initialization consists of parsing the PSCI OF node for the topology
> > and the "domain idle states" DT bindings. In case the idle states are
> > compatible with "domain-idle-state", the initialized genpd becomes
> > responsible of selecting an idle state for the PM domain, via assigning it
> > a genpd governor.
> >
> > Note that, a successful initialization of the genpd data structures, is
> > followed by a call to psci_set_osi_mode(), as to try to enable the OSI mode
> > in the PSCI FW. In case this fails, we fall back into a degraded mode
> > rather than bailing out and returning an error code.
> >
> > Co-developed-by: Lina Iyer <lina.iyer@xxxxxxxxxx>
> > Signed-off-by: Lina Iyer <lina.iyer@xxxxxxxxxx>
> > Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> > ---
> >
> > Changes in v4:
> > - None.
> >
> > ---
> > drivers/cpuidle/cpuidle-psci-domain.c | 267 ++++++++++++++++++++++++++
> > drivers/cpuidle/cpuidle-psci.c | 4 +-
> > drivers/cpuidle/cpuidle-psci.h | 5 +
> > 3 files changed, 274 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> > index 656ef3d59149..c2f94ba42222 100644
> > --- a/drivers/cpuidle/cpuidle-psci-domain.c
> > +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> > @@ -7,14 +7,281 @@
> > *
> > */
> >
> > +#define pr_fmt(fmt) "CPUidle PSCI: " fmt
> > +
> > #include <linux/cpu.h>
> > #include <linux/device.h>
> > #include <linux/kernel.h>
> > #include <linux/pm_domain.h>
> > #include <linux/pm_runtime.h>
> > +#include <linux/psci.h>
> > +#include <linux/slab.h>
> > +#include <linux/string.h>
> >
> > #include "cpuidle-psci.h"
> >
> > +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;
> > +
> > + /* If we have failed to enable OSI mode, then abort power off. */
> > + if (!osi_mode_enabled)
> > + return -EBUSY;
> > +
>
> Why is above check needed ? Shouldn't we have disable/remove pd of
> OSI is not enabled ?
Well, failing to enable OSI should in practice not happen, while it
theoretically it could.
My approach to this has been to fall back to use a "degraded mode",
which seems quite common for these kind of situations. The degraded
mode means, we are preventing domain states from being used.
More importantly, it also keeps the code registering the PM domains, a
bit simpler.
>
> > + if (!state->data)
> > + return 0;
> > +
> > + /* OSI mode is enabled, set the corresponding domain state. */
> > + pd_state = state->data;
> > + psci_set_domain_state(*pd_state);
> > +
> > + return 0;
> > +}
> > +
>
> [...]
>
> > +static const struct of_device_id psci_of_match[] __initconst = {
> > + { .compatible = "arm,psci" },
>
> I think we can drop the above one as it's for v0.1 which didn't support
> OSI.
Yeah, I do that.
>
> > + { .compatible = "arm,psci-0.2" },
> > + { .compatible = "arm,psci-1.0" },
> > + {}
> > +};
> > +
> > +static int __init psci_idle_init_domains(void)
> > +{
> > + struct device_node *np = of_find_matching_node(NULL, psci_of_match);
> > + struct device_node *node;
> > + int ret = 0, pd_count = 0;
> > +
> > + if (!np)
> > + return -ENODEV;
> > +
> > + /* Currently limit the hierarchical topology to be used in OSI mode. */
> > + if (!psci_has_osi_support())
> > + goto out;
> > +
> > + /*
> > + * Parse child nodes for the "#power-domain-cells" property and
> > + * initialize a genpd/genpd-of-provider pair when it's found.
> > + */
> > + for_each_child_of_node(np, node) {
> > + if (!of_find_property(node, "#power-domain-cells", NULL))
> > + continue;
> > +
> > + ret = psci_pd_init(node);
> > + if (ret)
> > + goto put_node;
> > +
> > + pd_count++;
> > + }
> > +
> > + /* Bail out if not using the hierarchical CPU topology. */
> > + if (!pd_count)
> > + goto out;
> > +
> > + /* Link genpd masters/subdomains to model the CPU topology. */
> > + ret = psci_pd_init_topology(np);
> > + if (ret)
> > + goto remove_pd;
> > +
> > + /* Try to enable OSI mode. */
> > + ret = psci_set_osi_mode();
> > + if (ret)
> > + pr_warn("failed to enable OSI mode: %d\n", ret);
>
> Same question as above: shouldn't we disable and goto remove_pd ?
See my answer above. Does it satisfy your concern?
If so, may I add your reviewed-by tag, for the next re-spin when I
have removed one of the compatible strings?
Kind regards
Uffe
