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From: Philipp Zabel <p.zabel@pengutronix.de>
To: Nicolas Frattaroli <frattaroli.nicolas@gmail.com>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>, Jaroslav Kysela <perex@perex.cz>,
	Takashi Iwai <tiwai@suse.com>, Heiko Stuebner <heiko@sntech.de>
Cc: linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Subject: Re: [PATCH v2 1/4] ASoC: rockchip: add support for i2s-tdm controller
Date: Mon, 23 Aug 2021 18:03:31 +0200	[thread overview]
Message-ID: <b596373b280dfe23a7e932b84ce31a2dbb806912.camel@pengutronix.de> (raw)
In-Reply-To: <9368735.gdWEK3B62L@archbook>

Hi Nicolas,

On Mon, 2021-08-23 at 16:35 +0200, Nicolas Frattaroli wrote:
[...]
> > I'm not too fond of reimplementing half a reset controller in here.
> > The reset framework does not support synchronized (de)assertion of
> > multiple reset controls, I wonder if this would be useful to add.
> > Without having thought about this too hard, I could imagine this as an
> > extension to the bulk API, or possibly a call to join multiple reset
> > controls into a reset control array.
> 
> I agree, the code required for synchronised reset seems to be a good
> candidate for a generalised solution elsewhere.
> However, I'm not sure if I'm the right candidate to design this API
> as my first kernel contribution when the board I'm currently testing
> this with doesn't even utilise the synchronized reset.
> 
> If I come across an opportunity to test synchronised resets, I'll
> definitely look into refactoring this. I'd also be happy to hear of
> any other driver which is currently implementing its own synchronised
> reset.
[...] 
> > What is the reason for the different delays in
> > rockchip_snd_xfer_sync_reset() and rockchip_snd_reset()?
> > 
> 
> Simply put: I have no idea. This is what downstream does, and it
> appears to work for me. The git history of the downstream kernel
> also doesn't tell me anything about why the sync reset is 150
> and this one is 1.
> 
> I've got no device to test the sync reset with at the moment so
> I'm wary of playing with the delay value.

Fair points. You could remove the untested synchronized reset support
for now; that would allow to get rid of the rockchip,cru device tree
property, which is only required to let this driver access the CRU
registers behind the clock/reset controller driver's back.

[...]
> > > +	if (i2s_tdm->clk_trcm != TRCM_TXRX) {
> > > +		cru_node = of_parse_phandle(node, "rockchip,cru", 0);
> > > +		i2s_tdm->cru_base = of_iomap(cru_node, 0);
> > 
> > This is a bit ugly if there is another driver sitting on the
> > rockchip,cru compatible node. Which reset controller driver is backing
> > the reset controls below?
> 
> I'm not sure if I understand the question (I only just today learned that
> reset controls have drivers) but I think the reset it is using in the
> Quartz64 dts is backed by rk3568-cru. Let me know if I misunderstood you.

That's the one, thanks.

The devm_reset_control_get() calls below follow the "reset-names"
and "resets" device tree properties. Those point (&cru) to a
clock-controller node with compatible = "rockchip,rk3568-cru".

The corresponding driver is drivers/clk/rockchip/clk-rk3568.c,
so the reset controller is provided by the reset_controller_register()
call in drivers/clk/rockchip/softrst.c.

regards
Philipp

  reply	other threads:[~2021-08-23 16:03 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-20 18:27 [PATCH v2 0/4] Rockchip I2S/TDM controller Nicolas Frattaroli
2021-08-20 18:27 ` [PATCH v2 1/4] ASoC: rockchip: add support for i2s-tdm controller Nicolas Frattaroli
2021-08-20 19:02   ` Pierre-Louis Bossart
2021-08-21 20:45     ` Nicolas Frattaroli
2021-08-23 11:19       ` Mark Brown
2021-08-23 15:02       ` Pierre-Louis Bossart
2021-08-23 12:03   ` Philipp Zabel
2021-08-23 14:35     ` Nicolas Frattaroli
2021-08-23 16:03       ` Philipp Zabel [this message]
2021-08-20 18:27 ` [PATCH v2 2/4] dt-bindings: sound: add rockchip i2s-tdm binding Nicolas Frattaroli
2021-08-24 16:42   ` Rob Herring
2021-08-20 18:27 ` [PATCH v2 3/4] arm64: dts: rockchip: add i2s1 on rk356x Nicolas Frattaroli
2021-08-20 18:27 ` [PATCH v2 4/4] arm64: dts: rockchip: add analog audio on Quartz64 Nicolas Frattaroli

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