Re: [PATCH v11]: clk: Add common clock support for Mediatek MT8135 and MT8173

From: Sascha Hauer <s.hauer@pengutronix.de>
To: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Mike Turquette <mturquette@linaro.org>,
	Stephen Boyd <sboyd@codeaurora.org>,
	YH Chen <yh.chen@mediatek.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Henry Chen <henryc.chen@mediatek.com>,
	linux-mediatek@lists.infradead.org,
	=Sascha Hauer <kernel@pengutronix.de>,
	Yingjoe Chen <Yingjoe.Chen@mediatek.com>,
	Eddie Huang <eddie.huang@mediatek.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v11]: clk: Add common clock support for Mediatek MT8135 and MT8173
Date: Tue, 14 Apr 2015 13:57:02 +0200	[thread overview]
Message-ID: <20150414115702.GX9742@pengutronix.de> (raw)
In-Reply-To: <CABuKBeLxcCcfcunwX7q=hSHRrrHd5-EMgRzSwhx9eSdvNKum=A@mail.gmail.com>

On Tue, Apr 14, 2015 at 01:01:30PM +0200, Matthias Brugger wrote:
> Hi Sascha,
> 
> 2015-04-14 12:08 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> > Hi Matthias,
> >
> > On Tue, Apr 07, 2015 at 01:47:58PM +0200, Matthias Brugger wrote:
> >> Hi Sascha,
> >>
> >>
> >> 2015-03-31 20:16 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> >> >
> >> > The following changes since commit 9eccca0843205f87c00404b663188b88eb248051:
> >> >
> >> >   Linux 4.0-rc3 (2015-03-08 16:09:09 -0700)
> >> >
> >> > are available in the git repository at:
> >> >
> >> >   git://git.pengutronix.de/git/imx/linux-2.6.git tags/v4.0-clk-mediatek-v11
> >> >
> >> > for you to fetch changes up to ae9129219143cfdefe8b3a463deb8c5cb8955525:
> >> >
> >> >   dt-bindings: ARM: Mediatek: Document devicetree bindings for clock/reset controllers (2015-03-31 20:08:46 +0200)
> >> >
> >> > ----------------------------------------------------------------
> >> > This patchset contains the initial common clock support for Mediatek SoCs.
> >> > Mediatek SoC's clock architecture comprises of various PLLs, dividers, muxes
> >> > and clock gates.
> >>
> >> I tried the patch set on my mt8135 eval board. I used the dts bindings
> >> from a former version of this set [1], but it does not boot the board
> >> (based on v4.0-rc7).
> >> Do you have any hint, what is happening, or are the bindings wrong?
> >
> > I just tried on a v4.0 with
> > - this series applied
> > - the dts patch applied (which is still up-to-date)
> > - multi_v7_defconfig
> >
> > And it still works. What do you mean with "does not boot the board"? No
> > console output? Could you try with earlyprintk?
> 
> The probelms I see is, that with the clock patches, I'm not able to
> boot into a initramfs [1].
> Whereas if I just comment topckgen and preicfg in the dts, I'm able to
> get the a serial console of my initramfs [2].
> 
> I wonder if you are able to get serial console from the initramfs with
> the clock patches + dts patch?

So you get kernel messages but no output from initramfs? In this case
the kernel disables the unused clocks in a late_initcall. The UART
driver still uses the dummy clock provided in the dtsi, so the real
UART clk gets disabled in the initcall. Try passing clk_ignore_unused to
the kernel

Sascha

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