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

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Date:   Thu, 3 Oct 2019 11:52:36 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     daniel.thompson@...aro.org, mathieu.poirier@...aro.org
Cc:     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 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.

Suzuki