linux-kernel - Re: [PATCH v2 2/2] mfd: madera: Wait for BOOT

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Message-ID: <20181002105602.GS1653@imbe.wolfsonmicro.main>
Date:   Tue, 2 Oct 2018 11:56:02 +0100
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
CC:     <lee.jones@...aro.org>, <patches@...nsource.cirrus.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] mfd: madera: Wait for BOOT_DONE before reading
 device ID

On Tue, Oct 02, 2018 at 11:41:34AM +0100, Richard Fitzgerald wrote:
> It isn't safe to read the device ID in the SOFTWARE_RESET
> register until the silicon boot sequence has completed. This
> patch rearranges the code to wait until BOOT_DONE is set.
> 
> If we don't have a hard reset line we want to defer writing a
> soft reset command until we have identified the silicon as
> something we recognize. As the BOOT_DONE bit is sticky it is
> safe to wait for it without issuing a soft reset first, because
> the most recent power-up will have caused a boot sequence and
> set the bit. Note that the boot sequence is not the same as a
> reset so we still have to soft reset to get the codec into a
> known state.
> 
> Signed-off-by: Stuart Henderson <stuarth@...nsource.cirrus.com>
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> ---

Reviewed-by: Charles Keepax <ckeepax@...nsource.cirrus.com>

Thanks,
Charles