linux-kernel - Re: [PATCH v2 04/12] clk: rockchip: rk3036: enable the CLK_IGNORE_UNUSED flag for sclk_i2s

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Date:	Fri, 08 Jan 2016 10:46:26 +0100
From:	Heiko Stuebner <heiko@...ech.de>
To:	Caesar Wang <caesar.upstream@...il.com>
Cc:	Caesar Wang <wxt@...k-chips.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	leecam@...gle.com, linux-arm-kernel@...ts.infradead.org,
	keescook@...gle.com, linux-clk@...r.kernel.org, leozwang@...gle.com
Subject: Re: [PATCH v2 04/12] clk: rockchip: rk3036: enable the CLK_IGNORE_UNUSED flag for sclk_i2s_out

Hi Caesar,

Am Freitag, 8. Januar 2016, 17:26:18 schrieb Caesar Wang:
> 在 2016年01月07日 18:05, Heiko Stuebner 写道:
> > Am Donnerstag, 7. Januar 2016, 16:25:47 schrieb Caesar Wang:
> >> SCLk_I2S_OUT is the noc bus clock for i2s module, this clock is used by
> >> extra codecs.
> >> 
> >> Due to it shouldn't belong to any driver, but we need it enabled,
> >> so just mark it as the CLK_IGNORE_UNUSED flag.
> > 
> > What makes you think it shouldn't belong to any driver?
> > 
> > In most schematics I have, i2s_clkout is going to some clock-input of
> > the
> > audio codec - probably the MCLK input on your rt5616. And while the new
> > rt5616 driver does not seem to do clock handling, it should just handle
> > the clock using the normal APIs.
> 
> You are right,  that's seem has to find the root cause.
> I'm wonder that the codec/i2s is working in kernel v4.1 patch without it.
> 
> In general,  the MLCK will be handled in i2s driver if the cpu side is
> master.

looking at the rt5616 datasheet, that would be BCLK1 instead I think. This 
one does differentiate between being master/slave.

The master/sysclk (mclk) is also handled in other drivers in all cases. 
(da7213.c, da7219.c, max98090.c, max98095.c, probably more)


Heiko