linux-kernel - Re: [PATCH] MIPS: ralink: manage low reset lines

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Message-ID: <20210204135919.GA13761@alpha.franken.de>
Date:   Thu, 4 Feb 2021 14:59:19 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Sander Vanheule <sander@...nheule.net>
Cc:     linux-mips@...r.kernel.org, John Crispin <john@...ozen.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: ralink: manage low reset lines

On Wed, Feb 03, 2021 at 10:21:41AM +0100, Sander Vanheule wrote:
> Reset lines with indices smaller than 8 are currently considered invalid
> by the rt2880-reset reset controller.
> 
> The MT7621 SoC uses a number of these low reset lines. The DTS defines
> reset lines "hsdma", "fe", and "mcm" with respective values 5, 6, and 2.
> As a result of the above restriction, these resets cannot be asserted or
> de-asserted by the reset controller. In cases where the bootloader does
> not de-assert these lines, this results in e.g. the MT7621's internal
> switch staying in reset.
> 
> Change the reset controller to only ignore the system reset, so all
> reset lines with index greater than 0 are considered valid.
> 
> Signed-off-by: Sander Vanheule <sander@...nheule.net>
> ---
> This patch was tested on a TP-Link EAP235-Wall, with an MT7621DA SoC.
> The bootloader on this device would leave reset line 2 ("mcm") asserted,
> which caused the internal switch to be unresponsive on an uninterrupted
> boot from flash.
> 
> When tftpboot was used in the bootloader to load an initramfs, it did
> initialise the internal switch, and cleared the mcm reset line. In this
> case the switch could be used from the OS. With this patch applied, the
> switch works both in an initramfs, and when (cold) booting from flash.
> 
>  arch/mips/ralink/reset.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

applied to mips-next.

Thomas.

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