RE: [PATCH V2 4/4] thermal: qoriq: Add clock operations

From: Anson Huang <anson.huang@nxp.com>
To: Fabio Estevam <festevam@gmail.com>
Cc: "rui.zhang" <rui.zhang@intel.com>,
	Eduardo Valentin <edubezval@gmail.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS 
	<devicetree@vger.kernel.org>,
	linux-kernel" <linux-kernel@vger.kernel.org>,
	dl-linux-imx <linux-imx@nxp.com>
Subject: RE: [PATCH V2 4/4] thermal: qoriq: Add clock operations
Date: Tue, 30 Jul 2019 04:33:27 +0000	[thread overview]
Message-ID: <DB3PR0402MB39169F3E70E928590C98C6A8F5DC0@DB3PR0402MB3916.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <CAOMZO5D33zPEu8zkq-KYvDv4Xzd8OoshSbzOCrBw1hwwJr-qNg@mail.gmail.com>

Hi, Fabio

> On Tue, Jul 30, 2019 at 12:00 AM Anson Huang <anson.huang@nxp.com>
> wrote:
> 
> > Shawn already applied the patch, and Abel has the AHB clock patch to
> > fix that, so just wait for the AHB clock patch in instead of revert the TMU
> clock patch?
> 
> Sorry, I don't understand Abel's patch as there is not a proper description of
> what it tries to fix.
> 
> If I understand correctly Abel's patch is not the proper fix and the real fix for
> the kernel TMU hang in linux-next is to manage the TMU clock inside the
> TMU driver, like you did in this patch.
> 
> To avoid a revert one possible solution would be to send only this one as a
> fix for 5.3. You can point that it Fixes the commit that adds i.MX8M support
> for the TMU driver.

I replied in the patch https://patchwork.kernel.org/patch/11032781/ , I pasted it as below,
The TMU clock is NOT the root cause, but it just accidently trigger this issue:

I can explain why Abel's patch can fix this issue, the AHB clock is a MUST always ON for system bus, while it does NOT have CLK_IS_CRITICAL flag set for now, when SDMA1 is probed, it will enable its clock, and the clk path is sdma1_clk->ipg_root->ahb, after SDMA1 probed done, it will disable its clock since no one use it, and it will trigger the ahb clock to be OFF, as its usecount is added by 1 when probe and decreased by 1 after
SDMA1 probe done, so usecount=0 will trigger AHB clock to be OFF.

So I think the best solution should be applying Abel's patch as you mentioned upper, the TMU clock patch is NOT the root cause, it just triggers this issue accidently☹

But I saw Abel's AHB patch is still under discussion, so I think we need to speed it up and make kernel boot up work for development. AHB/IPG are always critical for i.MX SoCs.

Thanks,
Anson.