linux-kernel - Re: [PATCHv9 2/3] arm64: dts: qcom: msm8998: Add Coresight support

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Date:   Thu, 3 Oct 2019 13:52:16 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     mathieu.poirier@...aro.org, saiprakash.ranjan@...eaurora.org,
        jeffrey.l.hugo@...il.com, mark.rutland@....com,
        rnayak@...eaurora.org, alexander.shishkin@...ux.intel.com,
        linux-arm-msm@...r.kernel.org, marc.w.gonzalez@...e.fr,
        linux-kernel@...r.kernel.org, bjorn.andersson@...aro.org,
        david.brown@...aro.org, agross@...nel.org, sibis@...eaurora.org,
        leo.yan@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCHv9 2/3] arm64: dts: qcom: msm8998: Add Coresight support

On Thu, Oct 03, 2019 at 11:52:36AM +0100, Suzuki K Poulose wrote:
> On 10/03/2019 11:20 AM, Daniel Thompson wrote:
> > On Wed, Oct 02, 2019 at 09:03:59AM -0600, Mathieu Poirier wrote:
> > > On Tue, 1 Oct 2019 at 12:05, Sai Prakash Ranjan
> > > <saiprakash.ranjan@...eaurora.org> wrote:
> > > > 
> > > > On 2019-10-01 11:01, Jeffrey Hugo wrote:
> > > > > On Tue, Oct 1, 2019 at 11:52 AM Sai Prakash Ranjan
> > > > > <saiprakash.ranjan@...eaurora.org> wrote:
> > > > > > 
> > > > > > 
> > > > > > Haan then likely it's the firmware issue.
> > > > > > We should probably disable coresight in soc dtsi and enable only for
> > > > > > MTP. For now you can add a status=disabled for all coresight nodes in
> > > > > > msm8998.dtsi and I will send the patch doing the same in a day or
> > > > > > two(sorry I am travelling currently).
> > > > > 
> > > > > This sounds sane to me (and is what I did while bisecting the issue).
> > > > > When you do create the patch, feel free to add the following tags as
> > > > > you see fit.
> > > > > 
> > > > > Reported-by: Jeffrey Hugo <jeffrey.l.hugo@...il.com>
> > > > > Tested-by: Jeffrey Hugo <jeffrey.l.hugo@...il.com>
> > > > 
> > > > Thanks Jeffrey, I will add them.
> > > > Hope Mathieu and Suzuki are OK with this.
> > > 
> > > The problem here is that a debug and production device are using the
> > > same device tree, i.e msm8998.dtsi.  Disabling coresight devices in
> > > the DTS file will allow the laptop to boot but completely disabled
> > > coresight blocks on the MTP board.  Leaving things as is breaks the
> > > laptop but allows coresight to be used on the MTP board.  One of three
> > > things can happen:
> > > 
> > > 1) Nothing gets done and production board can't boot without DTS modifications.
> > > 2) Disable tags are added to the DTS file and the debug board can't
> > > use coresight without modifications.
> > > 2) The handling of the debug power domain is done properly on the
> > > MSM8998 rather than relying on the bootloader to enable it.
> > > 3) The DTS file is split or reorganised to account for debug/production devices.
> > 
> > msm8998.dtsi is a SoC include file. Can't whatever default it adopts be
> > reversed in the board include files such as msm8998-mtp.dtsi or
> > msm8998-clamshell.dtsi ?
> 
> Or like Mathieu said, all the Coresight specific nodes could be moved in
> to say, msm8998-coresight.dtsi and could be included into the platforms
> where it actually works.

Sure, that works too.

Maybe it depends in you view the mtp as including the feature or as the
laptops as taking it away ;-) .

Treating it as a feature a board can disable also works nicely on systems
where the board include file should be setting secure-status a board
(although that's probably not the case for these boards since the
firmware is proprietary).


Daniel.