linux-kernel - Re: [PATCH] mfd: stm32-timers: avoid clearing auto reload register

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Date:   Tue, 23 Mar 2021 09:39:56 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Fabrice Gasnier <fabrice.gasnier@...s.st.com>
Cc:     vilhelm.gray@...il.com, alexandre.torgue@...s.st.com,
        mcoquelin.stm32@...il.com, olivier.moysan@...s.st.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH] mfd: stm32-timers: avoid clearing auto reload register

On Wed, 03 Mar 2021, Fabrice Gasnier wrote:

> The ARR register is cleared unconditionally upon probing, after the maximum
> value has been read. This initial condition is rather not intuitive, when
> considering the counter child driver. It rather expects the maximum value
> by default:
> - The counter interface shows a zero value by default for 'ceiling'
>   attribute.
> - Enabling the counter without any prior configuration makes it doesn't
>   count.
> 
> The reset value of ARR register is the maximum. So Choice here
> is to backup it, and restore it then, instead of clearing its value.
> It also fixes the initial condition seen by the counter driver.
> 
> Fixes: d0f949e220fd ("mfd: Add STM32 Timers driver")
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
> ---
>  drivers/mfd/stm32-timers.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)

Applied, thanks.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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