Re: [PATCH v2 2/4] platform/mellanox: mlxbf-pmc: Add support for 64-bit counters and cycle count

[Ilpo Järvinen]

On Mon, 20 May 2024, Shravan Kumar Ramani wrote:

> Add support for programming any counter to monitor the cycle count.
> Since counting of cycles using 32-bit ocunters would result in frequent

counters

> wraparounds, add the ability to combine 2 adjacent 32-bit counters to
> form 1 64-bit counter.
> Both these features are supported by BlueField-3 PMC hardware, hence
> the required bit-fields are exposed by the driver via sysfs to allow
> the user to configure as needed.

I'm trying to understand what happens for the other counter, when the 
use_odd_counter is enabled? This change also doesn't add code that would 
make the other counter -EBUSY, should that be done?

For 64-bit counter, I suppose the userspace is expected to read the full 
counter from two sysfs files and combine the value (your documentation 
doesn't explain this)? That seems non-optimal, why cannot kernel just 
return the full combined 64-value directly in kernel?

Similarly, are these cycle counters occupying the same space as non-cycle 
counters (so both can/cannot be used that the same time)? I'm asking this 
because you're adding a parallel interface to read the value and if it's 
either-or, I don't understand why the value needs to be read from 
different file depending on the counter counting in cycles or not.

-- 
 i.

> Signed-off-by: Shravan Kumar Ramani <shravankr@xxxxxxxxxx>
> Reviewed-by: David Thompson <davthompson@xxxxxxxxxx>
> Reviewed-by: Vadim Pasternak <vadimp@xxxxxxxxxx>
> ---
>  drivers/platform/mellanox/mlxbf-pmc.c | 134 ++++++++++++++++++++++++++
>  1 file changed, 134 insertions(+)
> 
> diff --git a/drivers/platform/mellanox/mlxbf-pmc.c b/drivers/platform/mellanox/mlxbf-pmc.c
> index 4ed9c7fd2b62..635ecc3b3845 100644
> --- a/drivers/platform/mellanox/mlxbf-pmc.c
> +++ b/drivers/platform/mellanox/mlxbf-pmc.c
> @@ -88,6 +88,8 @@
>  #define MLXBF_PMC_CRSPACE_PERFMON_CTL(n) (n * MLXBF_PMC_CRSPACE_PERFMON_REG0_SZ)
>  #define MLXBF_PMC_CRSPACE_PERFMON_EN BIT(30)
>  #define MLXBF_PMC_CRSPACE_PERFMON_CLR BIT(28)
> +#define MLXBF_PMC_CRSPACE_PERFMON_UOC GENMASK(15, 0)
> +#define MLXBF_PMC_CRSPACE_PERFMON_COUNT_CLOCK(n) (MLXBF_PMC_CRSPACE_PERFMON_CTL(n) + 0x4)
>  #define MLXBF_PMC_CRSPACE_PERFMON_VAL0(n) (MLXBF_PMC_CRSPACE_PERFMON_CTL(n) + 0xc)
>  
>  /**
> @@ -114,6 +116,8 @@ struct mlxbf_pmc_attribute {
>   * @attr_event: Attributes for "event" sysfs files
>   * @attr_event_list: Attributes for "event_list" sysfs files
>   * @attr_enable: Attributes for "enable" sysfs files
> + * @attr_use_odd_counter: Attributes for "use_odd_counter" sysfs files
> + * @attr_count_clock: Attributes for "count_clock" sysfs files
>   * @block_attr: All attributes needed for the block
>   * @block_attr_grp: Attribute group for the block
>   */
> @@ -126,6 +130,8 @@ struct mlxbf_pmc_block_info {
>  	struct mlxbf_pmc_attribute *attr_event;
>  	struct mlxbf_pmc_attribute attr_event_list;
>  	struct mlxbf_pmc_attribute attr_enable;
> +	struct mlxbf_pmc_attribute attr_use_odd_counter;
> +	struct mlxbf_pmc_attribute attr_count_clock;
>  	struct attribute *block_attr[MLXBF_PMC_MAX_ATTRS];
>  	struct attribute_group block_attr_grp;
>  };
> @@ -1763,6 +1769,103 @@ static ssize_t mlxbf_pmc_enable_store(struct device *dev,
>  	return count;
>  }
>  
> +/* Show function for "use_odd_counter" sysfs files - only for crspace */
> +static ssize_t mlxbf_pmc_use_odd_counter_show(struct device *dev,
> +					      struct device_attribute *attr, char *buf)
> +{
> +	struct mlxbf_pmc_attribute *attr_use_odd_counter = container_of(
> +		attr, struct mlxbf_pmc_attribute, dev_attr);
> +	unsigned int blk_num;
> +	u32 value, reg;
> +
> +	blk_num = attr_use_odd_counter->nr;
> +
> +	if (mlxbf_pmc_readl(pmc->block[blk_num].mmio_base +
> +			MLXBF_PMC_CRSPACE_PERFMON_CTL(pmc->block[blk_num].counters),
> +			&reg))
> +		return -EINVAL;
> +
> +	value = FIELD_GET(MLXBF_PMC_CRSPACE_PERFMON_UOC, reg);
> +
> +	return sysfs_emit(buf, "%u\n", value);
> +}
> +
> +/* Store function for "use_odd_counter" sysfs files - only for crspace */
> +static ssize_t mlxbf_pmc_use_odd_counter_store(struct device *dev,
> +					       struct device_attribute *attr,
> +					       const char *buf, size_t count)
> +{
> +	struct mlxbf_pmc_attribute *attr_use_odd_counter = container_of(
> +		attr, struct mlxbf_pmc_attribute, dev_attr);
> +	unsigned int blk_num;
> +	u32 uoc, reg;
> +	int err;
> +
> +	blk_num = attr_use_odd_counter->nr;
> +
> +	err = kstrtouint(buf, 0, &uoc);
> +	if (err < 0)
> +		return err;
> +
> +	err = mlxbf_pmc_readl(pmc->block[blk_num].mmio_base +
> +		MLXBF_PMC_CRSPACE_PERFMON_CTL(pmc->block[blk_num].counters),
> +		&reg);
> +	if (err)
> +		return -EINVAL;
> +
> +	reg &= ~MLXBF_PMC_CRSPACE_PERFMON_UOC;
> +	reg |= FIELD_PREP(MLXBF_PMC_CRSPACE_PERFMON_UOC, uoc);
> +
> +	mlxbf_pmc_write(pmc->block[blk_num].mmio_base +
> +		MLXBF_PMC_CRSPACE_PERFMON_CTL(pmc->block[blk_num].counters),
> +		MLXBF_PMC_WRITE_REG_32, reg);
> +
> +	return count;
> +}
> +
> +/* Show function for "count_clock" sysfs files - only for crspace */
> +static ssize_t mlxbf_pmc_count_clock_show(struct device *dev,
> +					  struct device_attribute *attr, char *buf)
> +{
> +	struct mlxbf_pmc_attribute *attr_count_clock = container_of(
> +		attr, struct mlxbf_pmc_attribute, dev_attr);
> +	unsigned int blk_num;
> +	u32 reg;
> +
> +	blk_num = attr_count_clock->nr;
> +
> +	if (mlxbf_pmc_readl(pmc->block[blk_num].mmio_base +
> +			MLXBF_PMC_CRSPACE_PERFMON_COUNT_CLOCK(pmc->block[blk_num].counters),
> +			&reg))
> +		return -EINVAL;
> +
> +	return sysfs_emit(buf, "%u\n", reg);
> +}
> +
> +/* Store function for "count_clock" sysfs files - only for crspace */
> +static ssize_t mlxbf_pmc_count_clock_store(struct device *dev,
> +					   struct device_attribute *attr,
> +					   const char *buf, size_t count)
> +{
> +	struct mlxbf_pmc_attribute *attr_count_clock = container_of(
> +		attr, struct mlxbf_pmc_attribute, dev_attr);
> +	unsigned int blk_num;
> +	u32 reg;
> +	int err;
> +
> +	blk_num = attr_count_clock->nr;
> +
> +	err = kstrtouint(buf, 0, &reg);
> +	if (err < 0)
> +		return err;
> +
> +	mlxbf_pmc_write(pmc->block[blk_num].mmio_base +
> +		MLXBF_PMC_CRSPACE_PERFMON_COUNT_CLOCK(pmc->block[blk_num].counters),
> +		MLXBF_PMC_WRITE_REG_32, reg);
> +
> +	return count;
> +}
> +
>  /* Populate attributes for blocks with counters to monitor performance */
>  static int mlxbf_pmc_init_perftype_counter(struct device *dev, unsigned int blk_num)
>  {
> @@ -1799,6 +1902,37 @@ static int mlxbf_pmc_init_perftype_counter(struct device *dev, unsigned int blk_
>  		attr = NULL;
>  	}
>  
> +	if (pmc->block[blk_num].type == MLXBF_PMC_TYPE_CRSPACE) {
> +		/*
> +		 * Couple adjacent odd and even 32-bit counters to form 64-bit counters
> +		 * using "use_odd_counter" sysfs which has one bit per even counter.
> +		 */
> +		attr = &pmc->block[blk_num].attr_use_odd_counter;
> +		attr->dev_attr.attr.mode = 0644;
> +		attr->dev_attr.show = mlxbf_pmc_use_odd_counter_show;
> +		attr->dev_attr.store = mlxbf_pmc_use_odd_counter_store;
> +		attr->nr = blk_num;
> +		attr->dev_attr.attr.name = devm_kasprintf(dev, GFP_KERNEL,
> +							  "use_odd_counter");
> +		if (!attr->dev_attr.attr.name)
> +			return -ENOMEM;
> +		pmc->block[blk_num].block_attr[++i] = &attr->dev_attr.attr;
> +		attr = NULL;
> +
> +		/* Program crspace counters to count clock cycles using "count_clock" sysfs */
> +		attr = &pmc->block[blk_num].attr_count_clock;
> +		attr->dev_attr.attr.mode = 0644;
> +		attr->dev_attr.show = mlxbf_pmc_count_clock_show;
> +		attr->dev_attr.store = mlxbf_pmc_count_clock_store;
> +		attr->nr = blk_num;
> +		attr->dev_attr.attr.name = devm_kasprintf(dev, GFP_KERNEL,
> +							  "count_clock");
> +		if (!attr->dev_attr.attr.name)
> +			return -ENOMEM;
> +		pmc->block[blk_num].block_attr[++i] = &attr->dev_attr.attr;
> +		attr = NULL;
> +	}