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Date: Tue, 25 Jan 2022 12:44:59 +0100 From: Ulf Hansson <ulf.hansson@...aro.org> To: Daniel Lezcano <daniel.lezcano@...aro.org> Cc: rjw@...ysocki.net, robh@...nel.org, lukasz.luba@....com, heiko@...ech.de, arnd@...aro.org, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>, Daniel Lezcano <daniel.lezcano@...nel.org> Subject: Re: [PATCH v6 2/5] powercap/drivers/dtpm: Add hierarchy creation On Tue, 25 Jan 2022 at 11:46, Daniel Lezcano <daniel.lezcano@...aro.org> wrote: > > On 24/01/2022 21:00, Ulf Hansson wrote: > > On Wed, 19 Jan 2022 at 09:58, Daniel Lezcano <daniel.lezcano@...aro.org> wrote: > >> > >> The DTPM framework is available but without a way to configure it. > >> > >> This change provides a way to create a hierarchy of DTPM node where > >> the power consumption reflects the sum of the children's power > >> consumption. > >> > >> It is up to the platform to specify an array of dtpm nodes where each > >> element has a pointer to its parent, except the top most one. The type > >> of the node gives the indication of which initialization callback to > >> call. At this time, we can create a virtual node, where its purpose is > >> to be a parent in the hierarchy, and a DT node where the name > >> describes its path. > >> > >> In order to ensure a nice self-encapsulation, the DTPM subsys array > >> contains a couple of initialization functions, one to setup the DTPM > >> backend and one to initialize it up. With this approach, the DTPM > >> framework has a very few material to export. > >> > >> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org> > >> --- > >> drivers/powercap/Kconfig | 1 + > >> drivers/powercap/dtpm.c | 168 ++++++++++++++++++++++++++++++++++++++- > >> include/linux/dtpm.h | 15 ++++ > >> 3 files changed, 181 insertions(+), 3 deletions(-) > >> > >> diff --git a/drivers/powercap/Kconfig b/drivers/powercap/Kconfig > >> index 8242e8c5ed77..b1ca339957e3 100644 > >> --- a/drivers/powercap/Kconfig > >> +++ b/drivers/powercap/Kconfig > >> @@ -46,6 +46,7 @@ config IDLE_INJECT > >> > >> config DTPM > >> bool "Power capping for Dynamic Thermal Power Management (EXPERIMENTAL)" > >> + depends on OF > >> help > >> This enables support for the power capping for the dynamic > >> thermal power management userspace engine. > >> diff --git a/drivers/powercap/dtpm.c b/drivers/powercap/dtpm.c > >> index 0e5c93443c70..10032f7132c4 100644 > >> --- a/drivers/powercap/dtpm.c > >> +++ b/drivers/powercap/dtpm.c > >> @@ -23,6 +23,7 @@ > >> #include <linux/powercap.h> > >> #include <linux/slab.h> > >> #include <linux/mutex.h> > >> +#include <linux/of.h> > >> > >> #include "dtpm_subsys.h" > >> > >> @@ -463,14 +464,175 @@ int dtpm_register(const char *name, struct dtpm *dtpm, struct dtpm *parent) > >> return 0; > >> } > >> > >> -static int __init init_dtpm(void) > >> +static struct dtpm *dtpm_setup_virtual(const struct dtpm_node *hierarchy, > >> + struct dtpm *parent) > >> { > >> + struct dtpm *dtpm; > >> + int ret; > >> + > >> + dtpm = kzalloc(sizeof(*dtpm), GFP_KERNEL); > >> + if (!dtpm) > >> + return ERR_PTR(-ENOMEM); > >> + dtpm_init(dtpm, NULL); > >> + > >> + ret = dtpm_register(hierarchy->name, dtpm, parent); > >> + if (ret) { > >> + pr_err("Failed to register dtpm node '%s': %d\n", > >> + hierarchy->name, ret); > >> + kfree(dtpm); > >> + return ERR_PTR(ret); > >> + } > >> + > >> + return dtpm; > >> +} > >> + > >> +static struct dtpm *dtpm_setup_dt(const struct dtpm_node *hierarchy, > >> + struct dtpm *parent) > >> +{ > >> + struct device_node *np; > >> + int i, ret; > >> + > >> + np = of_find_node_by_path(hierarchy->name); > >> + if (!np) { > >> + pr_err("Failed to find '%s'\n", hierarchy->name); > >> + return ERR_PTR(-ENXIO); > >> + } > >> + > >> + for (i = 0; i < ARRAY_SIZE(dtpm_subsys); i++) { > >> + > >> + if (!dtpm_subsys[i]->setup) > >> + continue; > >> + > >> + ret = dtpm_subsys[i]->setup(parent, np); > >> + if (ret) { > >> + pr_err("Failed to setup '%s': %d\n", dtpm_subsys[i]->name, ret); > >> + of_node_put(np); > >> + return ERR_PTR(ret); > >> + } > >> + } > >> + > >> + of_node_put(np); > >> + > >> + /* > >> + * By returning a NULL pointer, we let know the caller there > >> + * is no child for us as we are a leaf of the tree > >> + */ > >> + return NULL; > >> +} > >> + > >> +typedef struct dtpm * (*dtpm_node_callback_t)(const struct dtpm_node *, struct dtpm *); > >> + > >> +dtpm_node_callback_t dtpm_node_callback[] = { > >> + [DTPM_NODE_VIRTUAL] = dtpm_setup_virtual, > >> + [DTPM_NODE_DT] = dtpm_setup_dt, > >> +}; > >> + > >> +static int dtpm_for_each_child(const struct dtpm_node *hierarchy, > >> + const struct dtpm_node *it, struct dtpm *parent) > >> +{ > >> + struct dtpm *dtpm; > >> + int i, ret; > >> + > >> + for (i = 0; hierarchy[i].name; i++) { > >> + > >> + if (hierarchy[i].parent != it) > >> + continue; > >> + > >> + dtpm = dtpm_node_callback[hierarchy[i].type](&hierarchy[i], parent); > >> + if (!dtpm || IS_ERR(dtpm)) > > > > This can be tested with the "IS_ERR_OR_NULL()" macro. > > > >> + continue; > > > > We have discussed the error path previously. Just ignoring errors here > > and continuing with the initialization, isn't normally how we design > > good kernel code. > > > > However, you have also explained that the error path is special and > > somewhat non-trivial to manage in this case. I get that now and thanks > > for clarifying. > > > > Nevertheless, I think it deserves to be explained a bit with a comment > > in the code of what goes on here. Otherwise another developer that > > looks at this code in the future, may think it looks suspicious too. > > > >> + > >> + ret = dtpm_for_each_child(hierarchy, &hierarchy[i], dtpm); > >> + if (ret) > >> + return ret; > >> + } > >> + > >> + return 0; > >> +} > > > > [...] > > > > Other than the above, this looks good to me! > > With the above fixed, shall I add your reviewed-by ? Sure, that's fine! Kind regards Uffe
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