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

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Date:   Wed, 26 Oct 2022 04:10:30 +0000
From:   Trevor Wu (吳文良) <Trevor.Wu@...iatek.com>
To:     "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "broonie@...nel.org" <broonie@...nel.org>
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 Tue, 2022-10-25 at 12:18 +0200, AngeloGioacchino Del Regno wrote:
> Il 21/10/22 11:58, Trevor Wu (吳文良) ha scritto:
> > 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.
> > 
> 
> Is the power for register access enabled with a power domain?
> 
> Check drivers/clk/clk.c, grep for core->rpm_enabled.
> 
> If you enable runtime PM before registering the clocks, and you
> register them
> with the right struct device, the clock API will enable power for you
> before
> trying to read the clock enable status.
> 
> Regards,
> Angelo
> 

Hi Angelo,

I tried the way in MT8195, but it caused circular lock problem.

Because mtcmos depends on some clocks, clk_bulk_prepare_enable is also
used in scpsys_power_on()[1].
If the clock also depends on the power domain, this results in the
circular lock problem.
That's why I don't bind the power domain with these clocks.

[1] 
https://elixir.bootlin.com/linux/v6.1-rc2/source/drivers/soc/mediatek/mtk-pm-domains.c

Thanks,
Trevor