linux-kernel - Re: [PATCH 6/9] coresight-tpdm: Add node to set dsb programming mode

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Message-ID: <7302924e-21f9-8748-3d9e-854f4898d078@arm.com>
Date:   Mon, 24 Oct 2022 15:49:45 +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>,
        Konrad Dybcio <konradybcio@...il.com>,
        Mike Leach <mike.leach@...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,
        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
Subject: Re: [PATCH 6/9] coresight-tpdm: Add node to set dsb programming mode

On 08/09/2022 09:45, Tao Zhang wrote:
> Add node to set and show programming mode for TPDM DSB subunit.
> Once the DSB programming mode is set, it will be written to the
> register DSB_CR. Bit[10:9] of the DSB_CR register is used to set
> the DSB test mode.
> 
> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
> ---
>   drivers/hwtracing/coresight/coresight-tpdm.c | 49 +++++++++++++++++++++++++++-
>   drivers/hwtracing/coresight/coresight-tpdm.h | 10 ++++++
>   2 files changed, 58 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c b/drivers/hwtracing/coresight/coresight-tpdm.c
> index fae9963..7265793 100644
> --- a/drivers/hwtracing/coresight/coresight-tpdm.c
> +++ b/drivers/hwtracing/coresight/coresight-tpdm.c
> @@ -22,7 +22,7 @@ DEFINE_CORESIGHT_DEVLIST(tpdm_devs, "tpdm");
>   
>   static void tpdm_enable_dsb(struct tpdm_drvdata *drvdata)
>   {
> -	u32 val;
> +	u32 val, mode;
>   
>   	val = readl_relaxed(drvdata->base + TPDM_DSB_TIER);
>   	/* Set trigger timestamp */
> @@ -42,6 +42,19 @@ static void tpdm_enable_dsb(struct tpdm_drvdata *drvdata)
>   
>   	/* Set the enable bit of DSB control register to 1 */
>   	val = readl_relaxed(drvdata->base + TPDM_DSB_CR);
> +	/* Set the cycle accurate mode */
> +	mode = TPDM_DSB_MODE_CYCACC(drvdata->dsb->mode);
> +	val = val & ~(0x7 << 9);
> +	val = val | (mode << 9);

Please do not hard code numbers like that above. Please could
you define proper masks for the fields in DSB_CR and use
FIELD_GET, FIELD_PREP for setting the values.

> +	/* Set the byte lane for high-performance mode */
> +	mode = TPDM_DSB_MODE_HPBYTESEL(drvdata->dsb->mode);
> +	val = val & ~(0x1F << 2);
> +	val = val | (mode << 2);
> +	/* Set the performance mode */

Same as above.

> +	if (drvdata->dsb->mode & TPDM_DSB_MODE_PERF)
> +		val |= TPDM_DSB_MODE;
> +	else
> +		val &= ~TPDM_DSB_MODE;
>   	val |= TPDM_DSB_CR_ENA;
>   	writel_relaxed(val, drvdata->base + TPDM_DSB_CR);
>   }
> @@ -232,6 +245,39 @@ static struct attribute_group tpdm_attr_grp = {
>   	.attrs = tpdm_attrs,
>   };
>   
> +static ssize_t dsb_mode_show(struct device *dev,
> +				  struct device_attribute *attr,
> +				  char *buf)
> +{
> +	struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
> +
> +	if (!(drvdata->datasets & TPDM_PIDR0_DS_DSB))
> +		return -EPERM;

As mentioned earlier, use is_visble() instead of hard coding this
in every function.

> +
> +	return scnprintf(buf, PAGE_SIZE, "%lx\n",
> +			 (unsigned long)drvdata->dsb->mode);
> +}
> +
> +static ssize_t dsb_mode_store(struct device *dev,
> +				   struct device_attribute *attr,
> +				   const char *buf,
> +				   size_t size)
> +{
> +	struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
> +	unsigned long val;
> +
> +	if ((kstrtoul(buf, 16, &val)) || val < 0 || val > 3)

Why not leave kstrtoul to detect the base instead of always forcing
16 ? Some other code had forced to base of 10. Please be flexible
and avoid the inconsistencies.

> +		return -EINVAL;
> +	if (!(drvdata->datasets & TPDM_PIDR0_DS_DSB))
> +		return -EPERM;
> +
> +	spin_lock(&drvdata->spinlock);
> +	drvdata->dsb->mode = val & TPDM_MODE_ALL;
> +	spin_unlock(&drvdata->spinlock);
> +	return size;
> +}
> +static DEVICE_ATTR_RW(dsb_mode);
> +
>   static ssize_t dsb_trig_type_show(struct device *dev,
>   				     struct device_attribute *attr,
>   				     char *buf)
> @@ -312,6 +358,7 @@ static ssize_t dsb_trig_ts_store(struct device *dev,
>   }
>   static DEVICE_ATTR_RW(dsb_trig_ts);
>   static struct attribute *tpdm_dsb_attrs[] = {
> +	&dev_attr_dsb_mode.attr,
>   	&dev_attr_dsb_trig_ts.attr,
>   	&dev_attr_dsb_trig_type.attr,
>   	NULL,
> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.h b/drivers/hwtracing/coresight/coresight-tpdm.h
> index dd4a013..4d57488 100644
> --- a/drivers/hwtracing/coresight/coresight-tpdm.h
> +++ b/drivers/hwtracing/coresight/coresight-tpdm.h
> @@ -19,6 +19,14 @@
>   #define TPDM_DSB_XTRIG_TSENAB		BIT(1)
>   /* Enable bit for DSB subunit trigger type */
>   #define TPDM_DSB_TRIG_TYPE		BIT(12)
> +/* Enable bit for DSB subunit perfmance mode */
> +#define TPDM_DSB_MODE		BIT(1)
> +
> +/* DSB programming modes */
> +#define TPDM_DSB_MODE_CYCACC(val)	BMVAL(val, 0, 2)
> +#define TPDM_DSB_MODE_PERF		BIT(3)
> +#define TPDM_DSB_MODE_HPBYTESEL(val)	BMVAL(val, 4, 8)

Please could we use GENMASK to define the masks and
use FIELD_GET/FILED_PREP macros for the dealing with
the fields ?

Similarly for the DSB_CR register please.

Suzuki