linux-kernel - Re: [PATCH v3 2/2] clk: meson: add sub MMC clock controller driver

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Date:   Fri, 27 Jul 2018 09:45:51 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Yixun Lan <yixun.lan@...ogic.com>
Cc:     Rob Herring <robh@...nel.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        yixun.lan@...ogic.com, linux-kernel@...r.kernel.org,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Liang Yang <liang.yang@...ogic.com>,
        Qiufang Dai <qiufang.dai@...ogic.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Carlo Caione <carlo@...one.org>,
        linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, Jian Hu <jian.hu@...ogic.com>
Subject: Re: [PATCH v3 2/2] clk: meson: add sub MMC clock controller driver

Quoting Stephen Boyd (2018-07-27 09:41:40)
> Quoting Yixun Lan (2018-07-27 07:52:23)
> > HI Stephen:
> > 
> > On 07/26/2018 11:20 PM, Stephen Boyd wrote:
> > > Quoting Yixun Lan (2018-07-12 14:12:44)
> > >> diff --git a/drivers/clk/meson/mmc-clkc.c b/drivers/clk/meson/mmc-clkc.c
> > >> new file mode 100644
> > >> index 000000000000..36c4c7cd69a6
> > >> --- /dev/null
> > >> +++ b/drivers/clk/meson/mmc-clkc.c
> > >> @@ -0,0 +1,367 @@
> > >> +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> > >> +/*
> > >> + * Amlogic Meson MMC Sub Clock Controller Driver
> > >> + *
> > >> + * Copyright (c) 2017 Baylibre SAS.
> > >> + * Author: Jerome Brunet <jbrunet@...libre.com>
> > >> + *
> > >> + * Copyright (c) 2018 Amlogic, inc.
> > >> + * Author: Yixun Lan <yixun.lan@...ogic.com>
> > >> + */
> > >> +
> > >> +#include <linux/clk.h>
> > > 
> > > Is this include used?
> > > 
> > this is needed by clk_get_rate()
> > see drivers/clk/meson/mmc-clkc.c:204
> 
> Hmm ok. That's unfortunate.

You should be able to read the hardware to figure out the clk frequency?
This may be a sign that the phase clk_ops are bad and should be passing
in the frequency of the parent clk to the op so that phase can be
calculated. Jerome?