linux-kernel - Re: [PATCH v2 03/12] ASoC: mediatek: mt8188: support audsys clock

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Date:   Fri, 21 Oct 2022 09:58:09 +0000
From:   Trevor Wu (吳文良) <Trevor.Wu@...iatek.com>
To:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "tiwai@...e.com" <tiwai@...e.com>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 03/12] ASoC: mediatek: mt8188: support audsys clock

On Fri, 2022-10-21 at 10:41 +0200, AngeloGioacchino Del Regno wrote:
> Il 21/10/22 10:27, Trevor Wu ha scritto:
> > Add mt8188 audio cg clock control. Audio clock gates are registered
> > to CCF
> > for reference count and clock parent management.
> > 
> > Signed-off-by: Trevor Wu <trevor.wu@...iatek.com>
> > ---
> >   sound/soc/mediatek/mt8188/mt8188-audsys-clk.c | 206
> > ++++++++++++++++++
> >   sound/soc/mediatek/mt8188/mt8188-audsys-clk.h |  15 ++
> >   .../soc/mediatek/mt8188/mt8188-audsys-clkid.h |  83 +++++++
> >   3 files changed, 304 insertions(+)
> >   create mode 100644 sound/soc/mediatek/mt8188/mt8188-audsys-clk.c
> >   create mode 100644 sound/soc/mediatek/mt8188/mt8188-audsys-clk.h
> >   create mode 100644 sound/soc/mediatek/mt8188/mt8188-audsys-
> > clkid.h
> > 
> > diff --git a/sound/soc/mediatek/mt8188/mt8188-audsys-clk.c
> > b/sound/soc/mediatek/mt8188/mt8188-audsys-clk.c
> > new file mode 100644
> > index 000000000000..1f294231d4c2
> > --- /dev/null
> > +++ b/sound/soc/mediatek/mt8188/mt8188-audsys-clk.c
> > @@ -0,0 +1,206 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * mt8188-audsys-clk.c  --  MediaTek 8188 audsys clock control
> > + *
> > + * Copyright (c) 2022 MediaTek Inc.
> > + * Author: Chun-Chia Chiu <chun-chia.chiu@...iatek.com>
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/clk-provider.h>
> > +#include <linux/clkdev.h>
> > +#include "mt8188-afe-common.h"
> > +#include "mt8188-audsys-clk.h"
> > +#include "mt8188-audsys-clkid.h"
> > +#include "mt8188-reg.h"
> > +
> > +struct afe_gate {
> > +	int id;
> > +	const char *name;
> > +	const char *parent_name;
> > +	int reg;
> > +	u8 bit;
> > +	const struct clk_ops *ops;
> > +	unsigned long flags;
> > +	u8 cg_flags;
> > +};
> > +
> > +#define GATE_AFE_FLAGS(_id, _name, _parent, _reg, _bit, _flags,
> > _cgflags) {\
> > +		.id = _id,					\
> > +		.name = _name,					\
> > +		.parent_name = _parent,				\
> > +		.reg = _reg,					\
> > +		.bit = _bit,					\
> > +		.flags = _flags,				\
> > +		.cg_flags = _cgflags,				\
> > +	}
> > +
> > +#define GATE_AFE(_id, _name, _parent, _reg, _bit)		\
> > +	GATE_AFE_FLAGS(_id, _name, _parent, _reg, _bit,		\
> > +		       CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED,
> > CLK_GATE_SET_TO_DISABLE)
> 
> Can you please explain what's the reason for CLK_IGNORE_UNUSED here?
> Maybe we can solve some issue that you're facing in a cleaner way.
> 
> Regards,
> Angelo

Hi Angelo,

Because clk_disable_unused() calls clk_core_is_enabled(), register
access happens in is_enabled() ops.
At the moment, the power for register access is not enabled, so the
register read results in CPU hang.

That's why I added CLK_IGNORE_UNUSED here, but it can't resolve all
issues. Actually, we met same problem when "cat
/sys/kernel/debug/clk/clk_summary" is used. We are still suffering the
problem.

I'm not sure if I can implement clk ops by myself, and exclude the
registration of is_enabled() ops.

Thanks,
Trevor
>