linux-kernel - Re: [PATCH 13/14] mmc: meson-gx: work around clk-stop issue

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Message-ID: <7hzibbnjh6.fsf@baylibre.com>
Date:   Mon, 07 Aug 2017 14:41:57 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     Jerome Brunet <jbrunet@...libre.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Carlo Caione <carlo@...one.org>, linux-mmc@...r.kernel.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/14] mmc: meson-gx: work around clk-stop issue

Jerome Brunet <jbrunet@...libre.com> writes:

> It seems that the signal clock is also used and required, somehow, by
> the controller it self.
>
> It is shown during init, when writing to CFG while the divider is set
> to 0 will crash the SoC. During voltage switch, the controller may crash
> and the card may then fail to exit busy state if the clock is stopped.
>
> To avoid this, it is best to keep the clock running for the controller,
> except during rate change. However, we still need to be able to gate
> the clock out of the SoC. Let's use the pinmux for this, and fallback
> to gpio mode (pulled-down) when we need to gate the clock
>
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>

Curious "feature" of the IP, but the solution looks good to me.

Reviewed-by: Kevin Hilman <khilman@...libre.com>

Kevin