linux-kernel - Re: [PATCH v2 2/9] coresight-tpda: Add DSB dataset support

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Message-ID: <6072a788-74b9-6521-882c-c1637a68ccb2@arm.com>
Date:   Wed, 22 Feb 2023 12:46:16 +0000
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>,
        Konrad Dybcio <konradybcio@...il.com>,
        Mike Leach <mike.leach@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Jinlong Mao <quic_jinlmao@...cinc.com>,
        Leo Yan <leo.yan@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.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>,
        Hao Zhang <quic_hazha@...cinc.com>,
        linux-arm-msm@...r.kernel.org, bjorn.andersson@...aro.org,
        Tao Zhang <taozha@....qualcomm.com>
Subject: Re: [PATCH v2 2/9] coresight-tpda: Add DSB dataset support

On 19/01/2023 07:41, Tao Zhang wrote:
> Read the DSB element size from the device tree. Set the register
> bit that controls the DSB element size of the corresponding port.
> 
> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
> Signed-off-by: Tao Zhang <taozha@....qualcomm.com>
> ---
>   drivers/hwtracing/coresight/coresight-tpda.c | 62 ++++++++++++++++++++++++++++
>   drivers/hwtracing/coresight/coresight-tpda.h |  4 ++
>   2 files changed, 66 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tpda.c b/drivers/hwtracing/coresight/coresight-tpda.c
> index 5989798..be13e08 100644
> --- a/drivers/hwtracing/coresight/coresight-tpda.c
> +++ b/drivers/hwtracing/coresight/coresight-tpda.c
> @@ -37,6 +37,15 @@ static void tpda_enable_port(struct tpda_drvdata *drvdata, int port)
>   	u32 val;
>   
>   	val = readl_relaxed(drvdata->base + TPDA_Pn_CR(port));
> +	/*
> +	 * Configure aggregator port n DSB data set element size
> +	 * Set the bit to 0 if the size is 32
> +	 * Set the bit to 1 if the size is 64
> +	 */
> +	if (drvdata->dsb_esize[port] == 32)
> +		val &= ~TPDA_Pn_CR_DSBSIZE;
> +	else if (drvdata->dsb_esize[port] == 64)
> +		val |= TPDA_Pn_CR_DSBSIZE;

What are the chances of having a value other than 32 or 64 ?
What should we do in that case ? Should the driver at least
give out a warning at least in the unhandled case rather than
silently reusing the existing setting ?

Suzuki