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From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: saiprakash.ranjan@codeaurora.org, robh+dt@kernel.org,
	mathieu.poirier@linaro.org, leo.yan@linaro.org,
	alexander.shishkin@linux.intel.com, andy.gross@linaro.org,
	david.brown@linaro.org, vivek.gautam@codeaurora.org,
	dianders@chromium.org, sboyd@kernel.org,
	bjorn.andersson@linaro.org, devicetree@vger.kernel.org,
	mark.rutland@arm.com
Cc: rnayak@codeaurora.org, sibis@codeaurora.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCHv2 2/4] arm64: dts: qcom: msm8996: Add Coresight support
Date: Fri, 18 Jan 2019 12:04:20 +0000	[thread overview]
Message-ID: <1b7d4c2f-98f7-4b80-4e32-6e0fe5c906ce@arm.com> (raw)
In-Reply-To: <6543ad5c-bbcf-b3ec-332c-115e8e3d0825@codeaurora.org>

Hi,

On 18/01/2019 11:48, Sai Prakash Ranjan wrote:
> Hi Suzuki,
> 
> On 1/18/2019 4:27 PM, Suzuki K Poulose wrote:
>>
>> If you want to use the scatter-gather mode, you must add
>> "arm,scatter-gather"
>> property to the node here.
>>
>> Have you tested the scatter-gather mode on the chip ? Does that work at
>> all ?
>> Note: You could try this by setting a buffer_size > 1M for the ETR and use
>> it as a sink from the sysfs mode.
>>
> 
> Yes the chip supports scatter-gather mode[1]. But is it required in
> dt node since it's an optional property?

If you would like to use the scatter-gather mode, you must specify it
explicitly. We have had some other boards with broken scatter-gather
mode integration which causes mysterious issues when used. So we have
a white-list approach for enabling the scatter-gather mode in the driver.

So, if you have tested to make sure that the mode works fine with a recent
kernel version (v4.19 onwards), you may want to add the property.

Suzuki


  reply	other threads:[~2019-01-18 12:04 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-18  8:25 [PATCHv2 0/4] Add coresight support for SDM845 and MSM8996 Sai Prakash Ranjan
2019-01-18  8:25 ` [PATCHv2 1/4] arm64: dts: qcom: sdm845: Add Coresight support Sai Prakash Ranjan
2019-01-18  8:25 ` [PATCHv2 2/4] arm64: dts: qcom: msm8996: " Sai Prakash Ranjan
2019-01-18 10:57   ` Suzuki K Poulose
2019-01-18 11:48     ` Sai Prakash Ranjan
2019-01-18 12:04       ` Suzuki K Poulose [this message]
2019-01-18 12:08         ` Sai Prakash Ranjan
2019-01-18  8:25 ` [PATCHv2 3/4] coresight: etm4x: Add support to enable ETMv4.2 Sai Prakash Ranjan
2019-01-18  8:25 ` [PATCHv2 4/4] arm64: dts: qcom: sdm845: Remove the duplicate header inclusion Sai Prakash Ranjan

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