Re: [PATCH v2 1/7] dt-bindings: clock: Document T-Head TH1520 AP_SUBSYS controller

From: Icenowy Zheng <uwu@icenowy.me>
To: Drew Fustini <drew@pdp7.com>,
	Emil Renner Berthing <emil.renner.berthing@canonical.com>
Cc: Stephen Boyd <sboyd@kernel.org>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Conor Dooley <conor+dt@kernel.org>,
	Drew Fustini <dfustini@tenstorrent.com>, Fu Wei <wefu@redhat.com>,
	Guo Ren <guoren@kernel.org>, Jisheng Zhang <jszhang@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Rob Herring <robh@kernel.org>,
	Thomas Bonnefille <thomas.bonnefille@bootlin.com>,
	 Yangtao Li <frank.li@vivo.com>,
	linux-riscv@lists.infradead.org, linux-clk@vger.kernel.org,
	 devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	Conor Dooley <conor.dooley@microchip.com>
Subject: Re: [PATCH v2 1/7] dt-bindings: clock: Document T-Head TH1520 AP_SUBSYS controller
Date: Sat, 27 Jul 2024 13:21:39 +0800	[thread overview]
Message-ID: <2375ff5fb664d8de9627e76788bd40b5d8eabf35.camel@icenowy.me> (raw)
In-Reply-To: <ZqPQ8X51S6PrzQxI@x1>

在 2024-07-26星期五的 09:38 -0700，Drew Fustini写道：
> On Fri, Jul 26, 2024 at 03:45:36AM -0500, Emil Renner Berthing wrote:
> > Stephen Boyd wrote:
> > > Quoting Drew Fustini (2024-06-23 19:12:31)
> > > > Document bindings for the T-Head TH1520 AP sub-system clock
> > > > controller.
> > > > 
> > > > Link:
> > > > https://openbeagle.org/beaglev-ahead/beaglev-ahead/-/blob/main/docs/TH1520%20System%20User%20Manual.pdf
> > > > Co-developed-by: Yangtao Li <frank.li@vivo.com>
> > > > Signed-off-by: Yangtao Li <frank.li@vivo.com>
> > > > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > > > Signed-off-by: Drew Fustini <dfustini@tenstorrent.com>
> > > > ---
> > > 
> > > Applied to clk-next
> > 
> > Thanks, but this driver seems a bit incomplete. With this applied
> > the Lichee Pi
> > 4A no longer boots without the clk_ignore_unused kernel parameter.
> > 
> > /Emil
> 
> Is this the case when you apply the dts patches from this series?
> 
> The dts patches won't go in until 6.12 so I don't think the presence
> of
> the clk-th1520-ap.c itself in 6.11 would break existing systems.
> 
> That said, I have been using clk_ignore_unused. I had been thinking
> that
> made sense because the full set of clock controller drivers like
> AON_SUBSYS (always on), AUDIO_SUBSYS, DSP_SUBSYS, etc, are not
> present
> yet in mainline. However, the T-Head vendor kernel does have drivers
> for
> all those clock controllers and I was suprised to see that the vendor
> kernel fails to boot when I just tested removing clk_ignore_unused.
> 
> As for clk-th1520-ap.c in mainline, I'll investigate further which
> clk
> disables seem to causing the boot failure when using the dts from
> this
> series. I suspect I may need to add nodes that will cause the
> necessary
> clks to be enabled by their respective drivers.

If disabling the clock just leads to system hang, setting
CLK_IS_CRITICAL should be useful (and needed) here.

> 
> Thanks,
> Drew
> 
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