From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Saravana Kannan <saravanak@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>
Cc: kernel-team@android.com, linux-kernel@vger.kernel.org,
Jisheng Zhang <Jisheng.Zhang@synaptics.com>,
Kevin Hilman <khilman@baylibre.com>,
John Stultz <john.stultz@linaro.org>,
Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
Marc Zyngier <maz@kernel.org>,
'Linux Samsung SOC' <linux-samsung-soc@vger.kernel.org>,
Krzysztof Kozlowski <krzk@kernel.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default
Date: Mon, 11 Jan 2021 15:18:13 +0100 [thread overview]
Message-ID: <2556a69b-5da5-bf80-e051-df2d02fbc40f@samsung.com> (raw)
In-Reply-To: <5484316b-0f27-6c36-9259-5c765bb6b96c@samsung.com>
On 11.01.2021 12:12, Marek Szyprowski wrote:
> On 18.12.2020 04:17, Saravana Kannan wrote:
>> Cyclic dependencies in some firmware was one of the last remaining
>> reasons fw_devlink=on couldn't be set by default. Now that cyclic
>> dependencies don't block probing, set fw_devlink=on by default.
>>
>> Setting fw_devlink=on by default brings a bunch of benefits (currently,
>> only for systems with device tree firmware):
>> * Significantly cuts down deferred probes.
>> * Device probe is effectively attempted in graph order.
>> * Makes it much easier to load drivers as modules without having to
>> worry about functional dependencies between modules (depmod is still
>> needed for symbol dependencies).
>>
>> If this patch prevents some devices from probing, it's very likely due
>> to the system having one or more device drivers that "probe"/set up a
>> device (DT node with compatible property) without creating a struct
>> device for it. If we hit such cases, the device drivers need to be
>> fixed so that they populate struct devices and probe them like normal
>> device drivers so that the driver core is aware of the devices and their
>> status. See [1] for an example of such a case.
>>
>> [1] -
>> https://lore.kernel.org/lkml/CAGETcx9PiX==mLxB9PO8Myyk6u2vhPVwTMsA5NkD-ywH5xhusw@mail.gmail.com/
>> Signed-off-by: Saravana Kannan <saravanak@google.com>
>
> This patch landed recently in linux next-20210111 as commit
> e590474768f1 ("driver core: Set fw_devlink=on by default"). Sadly it
> breaks Exynos IOMMU operation, what causes lots of devices being
> deferred and not probed at all. I've briefly checked and noticed that
> exynos_sysmmu_probe() is never called after this patch. This is really
> strange for me, as the SYSMMU controllers on Exynos platform are
> regular platform devices registered by the OF code. The driver code is
> here: drivers/iommu/exynos-iommu.c, example dts:
> arch/arm/boot/dts/exynos3250.dtsi (compatible = "samsung,exynos-sysmmu").
Okay, I found the source of this problem. It is caused by Exynos power
domain driver, which is not platform driver yet. I will post a patch,
which converts it to the platform driver.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
next prev parent reply other threads:[~2021-01-11 14:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201218031703.3053753-1-saravanak@google.com>
[not found] ` <20201218031703.3053753-6-saravanak@google.com>
[not found] ` <CGME20210111111245eucas1p15acde7ecc2ca7f7782beb8ed74c72022@eucas1p1.samsung.com>
2021-01-11 11:12 ` [PATCH v1 5/5] driver core: Set fw_devlink=on by default Marek Szyprowski
[not found] ` <CGME20210111141814eucas1p1f388df07b789693a999042b27f0d8c2a@eucas1p1.samsung.com>
2021-01-11 14:18 ` Marek Szyprowski [this message]
2021-01-11 21:47 ` Saravana Kannan
2021-01-12 7:11 ` Marek Szyprowski
2021-01-12 20:51 ` Saravana Kannan
2021-01-13 7:04 ` Marek Szyprowski
2021-01-13 19:23 ` Saravana Kannan
2021-01-14 7:36 ` Marek Szyprowski
2021-01-14 18:08 ` Saravana Kannan
2021-01-18 17:43 ` Geert Uytterhoeven
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