linux-kernel - Re: [PATCH v6 3/4] clk: ralink: make system controller node a reset provider

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Date:   Mon, 10 Jan 2022 11:23:33 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Sergio Paracuellos <sergio.paracuellos@...il.com>
Cc:     "open list:COMMON CLK FRAMEWORK" <linux-clk@...r.kernel.org>,
        John Crispin <john@...ozen.org>, linux-staging@...ts.linux.dev,
        Greg KH <gregkh@...uxfoundation.org>,
        NeilBrown <neil@...wn.name>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Stephen Boyd <sboyd@...nel.org>
Subject: Re: [PATCH v6 3/4] clk: ralink: make system controller node a reset
 provider

On Mon, 2022-01-10 at 10:39 +0100, Sergio Paracuellos wrote:
[...]
> > Is this known to work for all possible users, without delay between
> > assert and deassert?
> 
> It seems it is. This is based on the original reset implementation for
> ralink. See:
> 
> https://elixir.bootlin.com/linux/v5.16/source/arch/mips/ralink/reset.c#L55
>
> > Are there any users of the reset_control_reset() API at all? This API
> > was added for self-clearing reset bits, so if there are no users that
> > need to pretend this is a reset pulse at the hardware level (there may
> > be), I'd prefer if this was just left out.
> 
> I am not following you here. What do you mean?

Looking at drivers/staging/mt7621-dts/mt7621.dtsi, it appears the
current reset users are:
  mediatek,mt7621-i2c
  ralink,mt7621-spi
  ralink,rt3883-gdma
  mediatek,mt7621-hsdma
  mediatek,mt7621-eth
  mediatek,mt7621
  mediatek,mt7621-pci

Many of the corresponding drivers use device_reset(), which is a
shorthand for requesting a reset control and calling
reset_control_reset() on it. That will call mt7621_reset_device, so it
is indeed used.

regards
Philipp