linux-kernel - Re: [PATCH v1 3/3] coresight-tpda: Optimize the function of reading element size

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Message-ID: <2fdaac53-3695-45cd-a57a-1afaf365a19a@arm.com>
Date: Mon, 8 Jul 2024 16:49:53 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Tao Zhang <quic_taozha@...cinc.com>,
 Mathieu Poirier <mathieu.poirier@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Mike Leach <mike.leach@...aro.org>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 James Clark <james.clark@....com>
Cc: Jinlong Mao <quic_jinlmao@...cinc.com>, Leo Yan <leo.yan@...aro.org>,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 Tingwei Zhang <quic_tingweiz@...cinc.com>,
 Yuanfang Zhang <quic_yuanfang@...cinc.com>,
 Trilok Soni <quic_tsoni@...cinc.com>, Song Chai <quic_songchai@...cinc.com>,
 linux-arm-msm@...r.kernel.org, Jie Gan <quic_jiegan@...cinc.com>
Subject: Re: [PATCH v1 3/3] coresight-tpda: Optimize the function of reading
 element size

On 05/07/2024 09:51, Tao Zhang wrote:
> Since the new funnel device supports multi-port output scenarios,
> there may be more than one TPDM connected to one TPDA. In this
> way, when reading the element size of the TPDM, TPDA driver needs
> to find the expected TPDM corresponding to the filter source.
> When TPDA finds a TPDM or a filter source from a input connection,
> it will read the Devicetree to get the expected TPDM's element
> size.
> 
> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
> ---
>   drivers/hwtracing/coresight/coresight-tpda.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tpda.c b/drivers/hwtracing/coresight/coresight-tpda.c
> index 52b0201090fb..fc5a4e46cf5d 100644
> --- a/drivers/hwtracing/coresight/coresight-tpda.c
> +++ b/drivers/hwtracing/coresight/coresight-tpda.c
> @@ -110,9 +110,12 @@ static int tpda_get_element_size(struct tpda_drvdata *drvdata,
>   		    csdev->pdata->in_conns[i]->dest_port != inport)
>   			continue;
>
		

> -		if (coresight_device_is_tpdm(in)) {
> +		if (coresight_device_is_tpdm(in)
> +		    || csdev->pdata->in_conns[i]->filter_src_dev) {

How can we assume that the filter-source device is always TPDM ?
It may be true for your test board, but driver must handle all
possible cases. I would rather prefer:

diff --git a/drivers/hwtracing/coresight/coresight-tpda.c 
b/drivers/hwtracing/coresight/coresight-tpda.c
index bfca103f9f84..b1d6f1dd60e3 100644
--- a/drivers/hwtracing/coresight/coresight-tpda.c
+++ b/drivers/hwtracing/coresight/coresight-tpda.c
@@ -110,6 +110,13 @@ static int tpda_get_element_size(struct 
tpda_drvdata *drvdata,
                     csdev->pdata->in_conns[i]->dest_port != inport)
                         continue;

+               /*
+                * If this port is tied to a source device,
+                * jump to that directly.
+                */
+               if (csdev->pdata->in_conns[i]->filter_src)
+                       in = csdev->pdata->in_conns[i]->filter_src;
+
                 if (coresight_device_is_tpdm(in)) {
                         if (drvdata->dsb_esize || drvdata->cmb_esize)
                                 return -EEXIST;


Suzuki