linux-kernel - Re: [PATCH v3 3/8] coresight-tpdm: Add CMB dataset support

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Message-ID: <f4ed3577-f78b-4b78-b306-8284ccb96043@arm.com>
Date: Mon, 18 Dec 2023 10:34:26 +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>, Song Chai <quic_songchai@...cinc.com>,
 linux-arm-msm@...r.kernel.org, andersson@...nel.org
Subject: Re: [PATCH v3 3/8] coresight-tpdm: Add CMB dataset support

On 21/11/2023 02:24, Tao Zhang wrote:
> CMB (continuous multi-bit) is one of TPDM's dataset type. CMB subunit
> can be enabled for data collection by writing 1 to the first bit of
> CMB_CR register. This change is to add enable/disable function for
> CMB dataset by writing CMB_CR register.
> 
> Reviewed-by: James Clark <james.clark@....com>
> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
> Signed-off-by: Jinlong Mao <quic_jinlmao@...cinc.com>
> ---
>   drivers/hwtracing/coresight/coresight-tpdm.c | 31 ++++++++++++++++++++
>   drivers/hwtracing/coresight/coresight-tpdm.h |  8 +++++
>   2 files changed, 39 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c b/drivers/hwtracing/coresight/coresight-tpdm.c
> index 97654aa4b772..c8bb38822e08 100644
> --- a/drivers/hwtracing/coresight/coresight-tpdm.c
> +++ b/drivers/hwtracing/coresight/coresight-tpdm.c
> @@ -131,6 +131,11 @@ static bool tpdm_has_dsb_dataset(struct tpdm_drvdata *drvdata)
>   	return (drvdata->datasets & TPDM_PIDR0_DS_DSB);
>   }
>   
> +static bool tpdm_has_cmb_dataset(struct tpdm_drvdata *drvdata)
> +{
> +	return (drvdata->datasets & TPDM_PIDR0_DS_CMB);
> +}
> +
>   static umode_t tpdm_dsb_is_visible(struct kobject *kobj,
>   				   struct attribute *attr, int n)
>   {
> @@ -267,6 +272,17 @@ static void tpdm_enable_dsb(struct tpdm_drvdata *drvdata)
>   	writel_relaxed(val, drvdata->base + TPDM_DSB_CR);
>   }
>   
> +static void tpdm_enable_cmb(struct tpdm_drvdata *drvdata)
> +{
> +	u32 val;
> +
> +	val = readl_relaxed(drvdata->base + TPDM_CMB_CR);
> +	val |= TPDM_CMB_CR_ENA;
> +
> +	/* Set the enable bit of CMB control register to 1 */
> +	writel_relaxed(val, drvdata->base + TPDM_CMB_CR);
> +}
> +
>   /*
>    * TPDM enable operations
>    * The TPDM or Monitor serves as data collection component for various
> @@ -281,6 +297,8 @@ static void __tpdm_enable(struct tpdm_drvdata *drvdata)
>   
>   	if (tpdm_has_dsb_dataset(drvdata))
>   		tpdm_enable_dsb(drvdata);
> +	if (tpdm_has_cmb_dataset(drvdata))
> +		tpdm_enable_cmb(drvdata);
>   

Don't we need to add this check in the "property read" section ?
Otherwise, we could generate warnings unnecessarily ?

i.e, if (tpdm_has_cmb_..())
	  rc |= fwnode_..read_property(cmb-elem-size...)

Similarly for DSB.

>   	CS_LOCK(drvdata->base);
>   }
> @@ -314,6 +332,17 @@ static void tpdm_disable_dsb(struct tpdm_drvdata *drvdata)
>   	writel_relaxed(val, drvdata->base + TPDM_DSB_CR);
>   }
>   
> +static void tpdm_disable_cmb(struct tpdm_drvdata *drvdata)
> +{
> +	u32 val;
> +
> +	val = readl_relaxed(drvdata->base + TPDM_CMB_CR);
> +	val &= ~TPDM_CMB_CR_ENA;
> +
> +	/* Set the enable bit of CMB control register to 0 */
> +	writel_relaxed(val, drvdata->base + TPDM_CMB_CR);
> +}
> +
>   /* TPDM disable operations */
>   static void __tpdm_disable(struct tpdm_drvdata *drvdata)
>   {
> @@ -321,6 +350,8 @@ static void __tpdm_disable(struct tpdm_drvdata *drvdata)
>   
>   	if (tpdm_has_dsb_dataset(drvdata))
>   		tpdm_disable_dsb(drvdata);
> +	if (tpdm_has_cmb_dataset(drvdata))
> +		tpdm_disable_cmb(drvdata);

minor nit: Instead of having these :

	if (tpdm_has_XY_()
		tpdm_{enable/disable}_XY_()
I prefer :

	tpdm_{enable/disable}_XY_

and the helper take care of returning early if the feature is
not present.


Suzuki


>   
>   	CS_LOCK(drvdata->base);
>   }
> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.h b/drivers/hwtracing/coresight/coresight-tpdm.h
> index 4115b2a17b8d..0098c58dfdd6 100644
> --- a/drivers/hwtracing/coresight/coresight-tpdm.h
> +++ b/drivers/hwtracing/coresight/coresight-tpdm.h
> @@ -9,6 +9,12 @@
>   /* The max number of the datasets that TPDM supports */
>   #define TPDM_DATASETS       7
>   
> +/* CMB Subunit Registers */
> +#define TPDM_CMB_CR		(0xA00)
> +
> +/* Enable bit for CMB subunit */
> +#define TPDM_CMB_CR_ENA		BIT(0)
> +
>   /* DSB Subunit Registers */
>   #define TPDM_DSB_CR		(0x780)
>   #define TPDM_DSB_TIER		(0x784)
> @@ -79,10 +85,12 @@
>    *
>    * PERIPHIDR0[0] : Fix to 1 if ImplDef subunit present, else 0
>    * PERIPHIDR0[1] : Fix to 1 if DSB subunit present, else 0
> + * PERIPHIDR0[2] : Fix to 1 if CMB subunit present, else 0
>    */
>   
>   #define TPDM_PIDR0_DS_IMPDEF	BIT(0)
>   #define TPDM_PIDR0_DS_DSB	BIT(1)
> +#define TPDM_PIDR0_DS_CMB	BIT(2)
>   
>   #define TPDM_DSB_MAX_LINES	256
>   /* MAX number of EDCR registers */