linux-kernel - Re: [PATCH v3 1/3] memory: tegra: Add devm_tegra_get_memory

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Message-ID: <f1658651-e3e1-388a-1d4c-a7fe04b27251@gmail.com>
Date:   Wed, 30 Sep 2020 18:27:00 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Nicolin Chen <nicoleotsuka@...il.com>
Cc:     joro@...tes.org, krzk@...nel.org, vdumpa@...dia.com,
        jonathanh@...dia.com, linux-tegra@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] memory: tegra: Add
 devm_tegra_get_memory_controller()

30.09.2020 18:23, Thierry Reding пишет:
> On Wed, Sep 30, 2020 at 01:42:56AM -0700, Nicolin Chen wrote:
>> From: Dmitry Osipenko <digetx@...il.com>
>>
>> Multiple Tegra drivers need to retrieve Memory Controller and hence there
>> is quite some duplication of the retrieval code among the drivers. Let's
>> add a new common helper for the retrieval of the MC.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
>> ---
>>
>> Changelog
>> v2->v3:
>>  * Replaced with Dimtry's devm_tegra_get_memory_controller()
>> v1->v2:
>>  * N/A
>>
>>  drivers/memory/tegra/mc.c | 39 +++++++++++++++++++++++++++++++++++++++
>>  include/soc/tegra/mc.h    | 17 +++++++++++++++++
>>  2 files changed, 56 insertions(+)
> 
> Let's not add this helper, please. If a device needs a reference to the
> memory controller, it should have a phandle to the memory controller in
> device tree so that it can be looked up explicitly.
> 
> Adding this helper is officially sanctioning that it's okay not to have
> that reference and that's a bad idea.

Maybe that's because the reference isn't really needed for the lookup? :)

Secondly, we could use the reference and then fall back to the
of-matching for devices that don't have the reference, like all Tegra20
devices + Tegra30/124 ACTMON devices.