From: Krzysztof Kozlowski <krzk@kernel.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: ulf.hansson@linaro.org, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Kevin Hilman <khilman@kernel.org>, Pavel Machek <pavel@ucw.cz>,
Len Brown <len.brown@intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
Stephen Boyd <sboyd@kernel.org>, Kukjin Kim <kgene@kernel.org>,
linux-pm@vger.kernel.org,
Vincent Guittot <vincent.guittot@linaro.org>,
nks@flawful.org, georgi.djakov@linaro.org,
Stephan Gerhold <stephan@gerhold.net>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org
Subject: Re: [PATCH V2 1/2] opp: Allow dev_pm_opp_get_opp_table() to return -EPROBE_DEFER
Date: Mon, 24 Aug 2020 11:17:24 +0200 [thread overview]
Message-ID: <20200824091724.GB20819@kozik-lap> (raw)
In-Reply-To: <24ff92dd1b0ee1b802b45698520f2937418f8094.1598260050.git.viresh.kumar@linaro.org>
On Mon, Aug 24, 2020 at 02:39:32PM +0530, Viresh Kumar wrote:
> From: Stephan Gerhold <stephan@gerhold.net>
>
> The OPP core manages various resources, e.g. clocks or interconnect paths.
> These resources are looked up when the OPP table is allocated once
> dev_pm_opp_get_opp_table() is called the first time (either directly
> or indirectly through one of the many helper functions).
>
> At this point, the resources may not be available yet, i.e. looking them
> up will result in -EPROBE_DEFER. Unfortunately, dev_pm_opp_get_opp_table()
> is currently unable to propagate this error code since it only returns
> the allocated OPP table or NULL.
>
> This means that all consumers of the OPP core are required to make sure
> that all necessary resources are available. Usually this happens by
> requesting them, checking the result and releasing them immediately after.
>
> For example, we have added "dev_pm_opp_of_find_icc_paths(dev, NULL)" to
> several drivers now just to make sure the interconnect providers are
> ready before the OPP table is allocated. If this call is missing,
> the OPP core will only warn about this and then attempt to continue
> without interconnect. This will eventually fail horribly, e.g.:
>
> cpu cpu0: _allocate_opp_table: Error finding interconnect paths: -517
> ... later ...
> of: _read_bw: Mismatch between opp-peak-kBps and paths (1 0)
> cpu cpu0: _opp_add_static_v2: opp key field not found
> cpu cpu0: _of_add_opp_table_v2: Failed to add OPP, -22
>
> This example happens when trying to use interconnects for a CPU OPP
> table together with qcom-cpufreq-nvmem.c. qcom-cpufreq-nvmem calls
> dev_pm_opp_set_supported_hw(), which ends up allocating the OPP table
> early. To fix the problem with the current approach we would need to add
> yet another call to dev_pm_opp_of_find_icc_paths(dev, NULL).
> But actually qcom-cpufreq-nvmem.c has nothing to do with interconnects...
>
> This commit attempts to make this more robust by allowing
> dev_pm_opp_get_opp_table() to return an error pointer. Fixing all
> the usages is trivial because the function is usually used indirectly
> through another helper (e.g. dev_pm_opp_set_supported_hw() above).
> These other helpers already return an error pointer.
>
> The example above then works correctly because set_supported_hw() will
> return -EPROBE_DEFER, and qcom-cpufreq-nvmem.c already propagates that
> error. It should also be possible to remove the remaining usages of
> "dev_pm_opp_of_find_icc_paths(dev, NULL)" from other drivers as well.
>
> Note that this commit currently only handles -EPROBE_DEFER for the
> clock/interconnects within _allocate_opp_table(). Other errors are just
> ignored as before. Eventually those should be propagated as well.
>
> Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
> [ Viresh: skip checking return value of dev_pm_opp_get_opp_table() for
> EPROBE_DEFER in domain.c, fix NULL return value and reorder
> code a bit in core.c, and update exynos-asv.c ]
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
> Stephan, I have made some changes to the code. Please try it again and
> lemme know if it works fine.
>
> drivers/base/power/domain.c | 14 +++++----
> drivers/opp/core.c | 53 +++++++++++++++++++-------------
> drivers/opp/of.c | 8 ++---
> drivers/soc/samsung/exynos-asv.c | 2 +-
> 4 files changed, 44 insertions(+), 33 deletions(-)
For Samsung:
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Best regards,
Krzysztof
next prev parent reply other threads:[~2020-08-24 9:17 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-24 9:09 [PATCH V2 1/2] opp: Allow dev_pm_opp_get_opp_table() to return -EPROBE_DEFER Viresh Kumar
2020-08-24 9:09 ` [PATCH V2 2/2] cpufreq: dt: Refactor initialization to handle probe deferral properly Viresh Kumar
[not found] ` <CGME20200901085708eucas1p231ccacd7b41685ece92ee21e3b726f28@eucas1p2.samsung.com>
2020-09-01 8:57 ` Marek Szyprowski
2020-09-01 9:45 ` Viresh Kumar
2020-09-01 10:05 ` Marek Szyprowski
2020-09-01 10:12 ` Viresh Kumar
2020-10-13 9:47 ` Geert Uytterhoeven
2020-10-13 9:56 ` Viresh Kumar
2020-10-14 16:40 ` Geert Uytterhoeven
2020-10-16 5:03 ` Viresh Kumar
2020-10-16 6:44 ` Geert Uytterhoeven
2020-10-16 8:07 ` Viresh Kumar
2020-10-27 16:29 ` Geert Uytterhoeven
2020-10-28 5:48 ` Viresh Kumar
2020-10-28 9:49 ` Geert Uytterhoeven
2020-10-28 9:52 ` Viresh Kumar
2020-08-24 9:17 ` Krzysztof Kozlowski [this message]
2020-08-24 11:08 ` [PATCH V2 1/2] opp: Allow dev_pm_opp_get_opp_table() to return -EPROBE_DEFER Ulf Hansson
2020-08-24 11:39 ` Stephan Gerhold
2020-10-15 18:05 ` Sudeep Holla
2020-10-16 4:24 ` Viresh Kumar
2020-10-16 6:00 ` Sudeep Holla
2020-10-16 11:12 ` Sudeep Holla
2020-10-16 15:28 ` Stephan Gerhold
2020-10-19 4:58 ` Viresh Kumar
2020-10-19 9:17 ` Sudeep Holla
2020-10-19 9:24 ` Viresh Kumar
2020-10-19 10:12 ` Sudeep Holla
2020-10-19 10:35 ` Viresh Kumar
2020-10-19 14:10 ` Sudeep Holla
2020-10-20 5:05 ` Viresh Kumar
2020-10-20 5:54 ` Viresh Kumar
2020-10-20 9:37 ` Sudeep Holla
2020-10-20 9:41 ` Viresh Kumar
2020-10-20 9:52 ` Sudeep Holla
2020-10-20 9:59 ` Viresh Kumar
2020-10-27 22:24 ` Guenter Roeck
2020-10-28 4:06 ` Viresh Kumar
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