linux-kernel - Re: [PATCH v3] reset: add support for non-DT systems

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Date:   Mon, 19 Feb 2018 10:41:48 -0600
From:   David Lechner <david@...hnology.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>,
        Bartosz Golaszewski <brgl@...ev.pl>
Cc:     linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...libre.com>
Subject: Re: [PATCH v3] reset: add support for non-DT systems

On 02/19/2018 07:13 AM, Philipp Zabel wrote:
> Hi Bartosz,
> 
> On Mon, 2018-02-19 at 13:34 +0100, Bartosz Golaszewski wrote:
>> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>
>> The reset framework only supports device-tree. There are some platforms
>> however, which need to use it even in legacy, board-file based mode.
>>
>> An example of such architecture is the DaVinci family of SoCs which
>> supports both device tree and legacy boot modes and we don't want to
>> introduce any regressions.
>>
>> We're currently working on converting the platform from its hand-crafted
>> clock API to using the common clock framework. Part of the overhaul will
>> be representing the chip's power sleep controller's reset lines using
>> the reset framework.
>>
>> This changeset extends the core reset code with a new field in the
>> reset controller struct which contains an array of lookup entries. Each
>> entry contains the device name, an additional, optional identifier
>> string and the reset id number.
>>
>> Drivers can register a set of reset lines using this lookup table and
>> concerned devices can access them using the regular reset_control API.
>>
>> This new function is only called as a fallback in case the of_node
>> field is NULL and doesn't change anything for current users.
>>
>> Tested with a dummy reset driver with several lookup entries.
>>
>> An example lookup table can look like this:
>>
>> static const struct reset_lookup foobar_reset_lookup[] = {
>> 	{ .dev = "foo",   .reset_id = "foo_id",    .id = 14 },
>> 	{ .dev = "bar",   .id = NULL,              .id = 3  },
>> 	{ }
>> };
> 
> Thank you for the patch. This is a useful addition, but the lookups
> should be added in platform code, not by the reset controller driver.
> 
> I would prefer reset_lookups to follow the patterns set by the other
> subsystem's lookup implementations:
> clk, gpiod, phy, and pwm have lookups that can be created from platform
> code, independently from the drivers (via clkdev_add_table,
> gpiod_add_lookup_table, phy_create_lookup, and pwm_add_table).
> 
> Following this pattern would allow to support reset controllers that are
> implemented as proper device drivers, and reset controllers that are
> reused on multiple platforms.
> 

When testing v2 of this series, I was thinking that having this sort
of separation would be better as well.