Messages in this thread | | | Date | Fri, 10 May 2024 10:54:25 +0200 | Subject | Re: [PATCH V2] OPP: Fix required_opp_tables for multiple genpds using same table | From | "Linux regression tracking (Thorsten Leemhuis)" <> |
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On 10.05.24 10:37, Ulf Hansson wrote: > On Thu, 9 May 2024 at 14:35, Thorsten Leemhuis > <regressions@leemhuis.info> wrote: >> On 12.04.24 08:41, Viresh Kumar wrote: >>> The required_opp_tables parsing is not perfect, as the OPP core does the >>> parsing solely based on the DT node pointers. >>> >>> The core sets the required_opp_tables entry to the first OPP table in >>> the "opp_tables" list, that matches with the node pointer. >>> >>> If the target DT OPP table is used by multiple devices and they all >>> create separate instances of 'struct opp_table' from it, then it is >>> possible that the required_opp_tables entry may be set to the incorrect >>> sibling device. >>> >>> Unfortunately, there is no clear way to initialize the right values >>> during the initial parsing and we need to do this at a later point of >>> time. >>> >>> Cross check the OPP table again while the genpds are attached and fix >>> them if required. >>> >>> Also add a new API for the genpd core to fetch the device pointer for >>> the genpd. >>> >>> Cc: Thorsten Leemhuis <regressions@leemhuis.info> >>> Reported-by: Vladimir Lypak <vladimir.lypak@gmail.com> >>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218682 >> >> Did this fall through the cracks? Just wondering, as from here it looks >> like for about four weeks now nothing happened to fix the regression >> linked above. But I might have missed something. Or is everybody waiting >> for a test from the reporter? > > I have chatted a bit with Viresh about this problem offlist, while > both me and him are/have been on vacations. Sorry for the delay and > confusion. > > The latest update from my side is that I am working on a solution, > that aim to remove the entire dev|devm_pm_opp_detach_genpd() API.
That sounds like something that would have to wait for a merge window; so given the timing I assume this would mean that the earliest point in time to merge this would be for 6.11-rc1, which is ~2 months away -- plus another 9 or 10 weeks until the fix would reach users.
> Instead, the plan is to move consumer drivers to use > dev_pm_domain_attach_list() to attach multiple PM domains per device. > When it comes to hooking up the required-opps-tables/devs, I think > genpd should be able to manage this during the device attach process. > In this way, consumer drivers shouldn't need to care about this at > all. > > That said, I am hoping that $subject patch should not be needed. > Although, I need a bit more time before I am ready to post a patchset > for the above. > > What do you think?
Given that the report is already more than a month old now and what I assumed above (which might be wrong), this makes me wonder: is there a downside if we apply this patch now, and simply revert this later when your proper solution is merged? I would assume that is what Linus want in this case to honor the "no regressions" rule.
Might be something different if this is something like a really odd corner case we assume nobody (or nearly nobody) will run into in practice. But as somebody noticed this, I assume that is not the case.
Ciao, Thorsten
>>> Co-developed-by: Vladimir Lypak <vladimir.lypak@gmail.com> >>> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> >>> --- >>> V2: >>> - Fix an `if` condition. >>> - s/Bugzilla/Closes/ and change ordering. >>> >>> drivers/opp/core.c | 31 ++++++++++++++++++++++++++++++- >>> drivers/pmdomain/core.c | 10 ++++++++++ >>> include/linux/pm_domain.h | 6 ++++++ >>> 3 files changed, 46 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/opp/core.c b/drivers/opp/core.c >>> index e233734b7220..cb4611fe1b5b 100644 >>> --- a/drivers/opp/core.c >>> +++ b/drivers/opp/core.c >>> @@ -2394,7 +2394,8 @@ static void _opp_detach_genpd(struct opp_table *opp_table) >>> static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev, >>> const char * const *names, struct device ***virt_devs) >>> { >>> - struct device *virt_dev; >>> + struct device *virt_dev, *gdev; >>> + struct opp_table *genpd_table; >>> int index = 0, ret = -EINVAL; >>> const char * const *name = names; >>> >>> @@ -2427,6 +2428,34 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev, >>> goto err; >>> } >>> >>> + /* >>> + * The required_opp_tables parsing is not perfect, as the OPP >>> + * core does the parsing solely based on the DT node pointers. >>> + * The core sets the required_opp_tables entry to the first OPP >>> + * table in the "opp_tables" list, that matches with the node >>> + * pointer. >>> + * >>> + * If the target DT OPP table is used by multiple devices and >>> + * they all create separate instances of 'struct opp_table' from >>> + * it, then it is possible that the required_opp_tables entry >>> + * may be set to the incorrect sibling device. >>> + * >>> + * Cross check it again and fix if required. >>> + */ >>> + gdev = dev_to_genpd_dev(virt_dev); >>> + if (IS_ERR(gdev)) >>> + return PTR_ERR(gdev); >>> + >>> + genpd_table = _find_opp_table(gdev); >>> + if (!IS_ERR(genpd_table)) { >>> + if (genpd_table != opp_table->required_opp_tables[index]) { >>> + dev_pm_opp_put_opp_table(opp_table->required_opp_tables[index]); >>> + opp_table->required_opp_tables[index] = genpd_table; >>> + } else { >>> + dev_pm_opp_put_opp_table(genpd_table); >>> + } >>> + } >>> + >>> /* >>> * Add the virtual genpd device as a user of the OPP table, so >>> * we can call dev_pm_opp_set_opp() on it directly. >>> diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c >>> index 4215ffd9b11c..c40eda92a85a 100644 >>> --- a/drivers/pmdomain/core.c >>> +++ b/drivers/pmdomain/core.c >>> @@ -184,6 +184,16 @@ static struct generic_pm_domain *dev_to_genpd(struct device *dev) >>> return pd_to_genpd(dev->pm_domain); >>> } >>> >>> +struct device *dev_to_genpd_dev(struct device *dev) >>> +{ >>> + struct generic_pm_domain *genpd = dev_to_genpd(dev); >>> + >>> + if (IS_ERR(genpd)) >>> + return ERR_CAST(genpd); >>> + >>> + return &genpd->dev; >>> +} >>> + >>> static int genpd_stop_dev(const struct generic_pm_domain *genpd, >>> struct device *dev) >>> { >>> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h >>> index 772d3280d35f..f24546a3d3db 100644 >>> --- a/include/linux/pm_domain.h >>> +++ b/include/linux/pm_domain.h >>> @@ -260,6 +260,7 @@ int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd, >>> int pm_genpd_init(struct generic_pm_domain *genpd, >>> struct dev_power_governor *gov, bool is_off); >>> int pm_genpd_remove(struct generic_pm_domain *genpd); >>> +struct device *dev_to_genpd_dev(struct device *dev); >>> int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state); >>> int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb); >>> int dev_pm_genpd_remove_notifier(struct device *dev); >>> @@ -307,6 +308,11 @@ static inline int pm_genpd_remove(struct generic_pm_domain *genpd) >>> return -EOPNOTSUPP; >>> } >>> >>> +static inline struct device *dev_to_genpd_dev(struct device *dev) >>> +{ >>> + return ERR_PTR(-EOPNOTSUPP); >>> +} >>> + >>> static inline int dev_pm_genpd_set_performance_state(struct device *dev, >>> unsigned int state) >>> { > >
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