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Date:   Mon, 22 Feb 2021 15:57:31 -0700
From:   Mathieu Poirier <mathieu.poirier@linaro.org>
To:     Mike Leach <mike.leach@linaro.org>
Cc:     linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org,
        linux-doc@vger.kernel.org, suzuki.poulose@arm.com,
        gregkh@linuxfoundation.org, alexander.shishkin@linux.intel.com,
        yabinc@google.com, corbet@lwn.net, linux-kernel@vger.kernel.org,
        tingwei@codeaurora.org, leo.yan@linaro.org
Subject: Re: [PATCH v4 03/10] coresight: config: Add configuration and
 feature generic functions
Message-ID: <20210222225731.GB3237327@xps15>
References: <20210128170936.9222-1-mike.leach@linaro.org>
 <20210128170936.9222-4-mike.leach@linaro.org>
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In-Reply-To: <20210128170936.9222-4-mike.leach@linaro.org>
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On Thu, Jan 28, 2021 at 05:09:29PM +0000, Mike Leach wrote:
> Adds a set of generic support functions that allow devices to set and save
> features values on the device, and enable and disable configurations.
> 
> Additional functions for other common operations including feature
> reset.
> 
> Signed-off-by: Mike Leach <mike.leach@linaro.org>
> ---
>  drivers/hwtracing/coresight/Makefile          |   2 +-
>  .../hwtracing/coresight/coresight-config.c    | 245 ++++++++++++++++++
>  .../hwtracing/coresight/coresight-config.h    |  14 +-
>  .../hwtracing/coresight/coresight-syscfg.c    |   5 +-
>  4 files changed, 262 insertions(+), 4 deletions(-)
>  create mode 100644 drivers/hwtracing/coresight/coresight-config.c
> 
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index 4ce854c434b1..daad9f103a78 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -4,7 +4,7 @@
>  #
>  obj-$(CONFIG_CORESIGHT) += coresight.o
>  coresight-y := coresight-core.o  coresight-etm-perf.o coresight-platform.o \
> -		coresight-sysfs.o coresight-syscfg.o
> +		coresight-sysfs.o coresight-syscfg.o coresight-config.o
>  obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o
>  coresight-tmc-y := coresight-tmc-core.o coresight-tmc-etf.o \
>  		      coresight-tmc-etr.o
> diff --git a/drivers/hwtracing/coresight/coresight-config.c b/drivers/hwtracing/coresight/coresight-config.c
> new file mode 100644
> index 000000000000..6cc4b213d9b6
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-config.c
> @@ -0,0 +1,245 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright(C) 2020 Linaro Limited. All rights reserved.
> + * Author: Mike Leach <mike.leach@linaro.org>
> + */
> +
> +#include <linux/sysfs.h>
> +#include "coresight-config.h"
> +#include "coresight-priv.h"
> +
> +/*
> + * Write the value held in the register structure into the driver internal memory
> + * location.
> + */
> +static void cscfg_set_reg(struct cscfg_reg_csdev *reg)
> +{
> +	u32 *p_val32 = (u32 *)reg->drv_store;
> +	u32 tmp32 = reg->value.val32;
> +
> +	if (reg->value.type & CS_CFG_REG_TYPE_VAL_64BIT) {
> +		*((u64 *)reg->drv_store) = reg->value.val64;
> +		return;
> +	}
> +
> +	if (reg->value.type & CS_CFG_REG_TYPE_VAL_MASK) {
> +		tmp32 = *p_val32;
> +		tmp32 &= ~reg->value.mask32;
> +		tmp32 |= reg->value.val32 & reg->value.mask32;
> +	}
> +	*p_val32 = tmp32;
> +}
> +
> +/*
> + * Read the driver value into the reg if this is marked as one we want to save.
> + */
> +static void cscfg_save_reg(struct cscfg_reg_csdev *reg)
> +{
> +	if (!(reg->value.type & CS_CFG_REG_TYPE_VAL_SAVE))
> +		return;
> +	if (reg->value.type & CS_CFG_REG_TYPE_VAL_64BIT)
> +		reg->value.val64 = *(u64 *)(reg->drv_store);
> +	else
> +		reg->value.val32 = *(u32 *)(reg->drv_store);
> +}
> +
> +static void cscfg_init_reg_param(struct cscfg_parameter_csdev *param_csdev,
> +				 struct cscfg_reg_csdev *reg_csdev)
> +{
> +	param_csdev->reg = reg_csdev;

This is the link between registers and parameters... Very important and very
easy to miss.  I'm not use how the situation can be improved other than adding a
comment to highlight the dependency. 

> +	param_csdev->val64 = reg_csdev->value.type & CS_CFG_REG_TYPE_VAL_64BIT;
> +
> +	if (param_csdev->val64)
> +		param_csdev->reg->value.val64 = param_csdev->current_value;
> +	else
> +		param_csdev->reg->value.val32 = (u32)param_csdev->current_value;
> +}
> +
> +/* set values into the driver locations referenced in cscfg_reg_csdev */
> +static int cscfg_set_on_enable(struct cscfg_feature_csdev *feat)
> +{
> +	int i;
> +
> +	spin_lock(feat->csdev_spinlock);
> +	for (i = 0; i < feat->nr_regs; i++)
> +		cscfg_set_reg(&feat->regs[i]);
> +	spin_unlock(feat->csdev_spinlock);
> +	dev_dbg(&feat->csdev->dev, "Feature %s: %s", feat->desc->name, "set on enable");
> +	return 0;
> +}
> +
> +/* copy back values from the driver locations referenced in cscfg_reg_csdev */
> +static void cscfg_save_on_disable(struct cscfg_feature_csdev *feat)

static void cscfg_save_on_disable(struct cscfg_feature_csdev *feat_csdev)

To be modified throughout the patchset. 


> +{
> +	int i;
> +
> +	spin_lock(feat->csdev_spinlock);
> +	for (i = 0; i < feat->nr_regs; i++)
> +		cscfg_save_reg(&feat->regs[i]);
> +	spin_unlock(feat->csdev_spinlock);
> +	dev_dbg(&feat->csdev->dev, "Feature %s: %s", feat->desc->name, "save on disable");
> +}
> +
> +/* default reset - restore default values */
> +void cscfg_reset_feat(struct cscfg_feature_csdev *feat)
> +{
> +	struct cscfg_parameter_csdev *param_csdev;
> +	struct cscfg_regval_desc *reg_desc;
> +	struct cscfg_reg_csdev *reg_csdev;
> +	int i;
> +
> +	/*
> +	 * set the default values for all parameters and regs from the
> +	 * relevant static descriptors.
> +	 */
> +	for (i = 0; i < feat->nr_params; i++)
> +		feat->params[i].current_value = feat->desc->params[i].value;
> +
> +	for (i = 0; i < feat->nr_regs; i++) {
> +		reg_desc = &feat->desc->regs[i];
> +		reg_csdev = &feat->regs[i];
> +		reg_csdev->value.type = reg_desc->type;
> +
> +		/* check if reg set from a parameter otherwise desc default */
> +		if (reg_desc->type & CS_CFG_REG_TYPE_VAL_PARAM) {
> +			/* for param, reg_desc->val32 is an index */

Overloading reg_desc->val32 into an index will make maintenance of this code
impossible.  Please see if there is a way to make that more intuitive.

> +			param_csdev = &feat->params[reg_desc->val32];
> +			cscfg_init_reg_param(param_csdev, reg_csdev);
> +		} else
> +			reg_csdev->value.val64 = reg_desc->val64;

Very subtle how 32 bit values and mask are also handle by the above line.
Probably worth a comment.

> +	}
> +}
> +
> +static int cscfg_update_presets(struct cscfg_config_csdev *cfg, int preset)

static int cscfg_update_presets(struct cscfg_config_csdev *cfg_csdev, ...

And throughout the patchset.

> +{
> +	int i, j, line_offset = 0, val_idx = 0, max_idx;
> +	struct cscfg_parameter_csdev *param;
> +	struct cscfg_feature_csdev *feat;
> +	const char *name;
> +	u64 val;
> +
> +	if (preset > cfg->desc->nr_presets)
> +		return -EINVAL;

A preset < 0 should also be treated as an error.

> +	/*
> +	 * Go through the array of features, assigning preset values to
> +	 * feature parameters in the order they appear.
> +	 * There should be precisely the same number of preset values as the
> +	 * sum of number of parameters over all the features - but we will
> +	 * ensure there is no overrun.
> +	 */
> +	line_offset = (preset-1) * cfg->desc->nr_total_params;

        line_offset = (preset - 1) * cfg->desc->nr_total_params; 

> +	max_idx = cfg->desc->nr_total_params;
> +	for (i = 0; i < cfg->nr_feat; i++) {
> +		feat = cfg->feats[i];
> +		if (!feat->nr_params)
> +			continue;
> +
> +		for (j = 0; j < feat->nr_params; j++) {
> +			param = &feat->params[j];
> +			name = feat->desc->params[j].name;
> +			val = cfg->desc->presets[line_offset + val_idx++];
> +			if (param->val64) {
> +				dev_dbg(&cfg->csdev->dev,
> +					"set param %s (%lld)", name, val);
> +				param->reg->value.val64 = val;
> +			} else {
> +				param->reg->value.val32 = (u32)val;
> +				dev_dbg(&cfg->csdev->dev,
> +					"set param %s (%d)", name, (u32)val);
> +			}
> +			if (val_idx >= max_idx)
> +				break;
> +		}
> +
> +		/* don't overrun the preset array line */
> +		if (val_idx >= max_idx)
> +			break;
> +	}
> +	return 0;
> +}
> +
> +/*
> + * if we are not using a preset, then need to update the feature params
> + * with current values.
> + */
> +static int cscfg_update_curr_params(struct cscfg_config_csdev *cfg)
> +{
> +	int i, j;
> +	struct cscfg_feature_csdev *feat;
> +	struct cscfg_parameter_csdev *param;
> +	const char *name;
> +	u64 val;
> +
> +	for (i = 0; i < cfg->nr_feat; i++) {
> +		feat = cfg->feats[i];
> +		if (!feat->nr_params)
> +			continue;
> +		for (j = 0; j < feat->nr_params; j++) {
> +			param = &feat->params[j];
> +			name = feat->desc->params[j].name;
> +			val = param->current_value;
> +			if (param->val64) {
> +				dev_dbg(&cfg->csdev->dev,
> +					"set param %s (%lld)", name, val);
> +				param->reg->value.val64 = val;
> +			} else {
> +				param->reg->value.val32 = (u32)val;
> +				dev_dbg(&cfg->csdev->dev,
> +					"set param %s (%d)", name, (u32)val);
> +			}
> +		}
> +	}
> +	return 0;
> +}
> +
> +static int cscfg_prog_config(struct cscfg_config_csdev *cfg, bool enable)
> +{
> +	int i, err = 0;
> +	struct cscfg_feature_csdev *feat;
> +	struct coresight_device *csdev;
> +
> +	for (i = 0; i < cfg->nr_feat; i++) {
> +		feat = cfg->feats[i];
> +		csdev = feat->csdev;
> +		dev_dbg(&csdev->dev, "cfg %s;  %s feature:%s", cfg->desc->name,
> +			enable ? "enable" : "disable", feat->desc->name);
> +
> +		if (enable)
> +			err = cscfg_set_on_enable(feat);
> +		else
> +			cscfg_save_on_disable(feat);
> +
> +		if (err)
> +			break;
> +	}
> +	return err;
> +}
> +
> +/**
> + * Enable configuration for the device.
> + *
> + * @cfg:	config_csdev to set.
> + * @preset:	preset values to use - 0 for default.
> + */
> +int cscfg_csdev_enable_config(struct cscfg_config_csdev *cfg, int preset)
> +{
> +	int err = 0;
> +
> +	if (preset)
> +		err = cscfg_update_presets(cfg, preset);
> +	else
> +		err = cscfg_update_curr_params(cfg);
> +	if (!err)
> +		err = cscfg_prog_config(cfg, true);
> +	if (!err)
> +		cfg->enabled = true;
> +	return err;
> +}
> +
> +void cscfg_csdev_disable_config(struct cscfg_config_csdev *cfg)
> +{
> +	if (cfg->enabled) {
> +		cscfg_prog_config(cfg, false);
> +		cfg->enabled = false;
> +	}
> +}
> diff --git a/drivers/hwtracing/coresight/coresight-config.h b/drivers/hwtracing/coresight/coresight-config.h
> index 75ecdecf7013..9d66e0071f38 100644
> --- a/drivers/hwtracing/coresight/coresight-config.h
> +++ b/drivers/hwtracing/coresight/coresight-config.h
> @@ -53,7 +53,10 @@ struct cscfg_parameter_desc {
>  };
>  
>  /**
> - * Representation of register value.
> + * Representation of register value and a descriptor of register usage.
> + *
> + * Used as a descriptor in the feature descriptors.
> + * Used as a value in when in a feature loading into a csdev.

Please move this to patch 01.

>   *
>   * Supports full 64 bit register value, or 32 bit value with optional mask
>   * value.
> @@ -262,4 +265,13 @@ struct cscfg_csdev_feat_ops {
>  			 struct cscfg_feature_csdev *feat);
>  };
>  
> +/* coresight config helper functions*/
> +
> +/* enable / disable config on a device - called with appropriate locks set.*/
> +int cscfg_csdev_enable_config(struct cscfg_config_csdev *cfg, int preset);
> +void cscfg_csdev_disable_config(struct cscfg_config_csdev *cfg);
> +
> +/* reset a feature to default values */
> +void cscfg_reset_feat(struct cscfg_feature_csdev *feat);
> +
>  #endif /* _CORESIGHT_CORESIGHT_CONFIG_H */
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> index c04cea0c1db2..4b8e4e35e3e7 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -198,14 +198,15 @@ static int cscfg_load_feat_csdev(struct coresight_device *csdev,
>  	if (!feat_csdev)
>  		return -ENOMEM;
>  
> -	/* load the feature into the device - may modify default ops*/
> +	/* load the feature into the device */

The right comment should be added in patch 02 and not changed without code to
sustain it.

A rigorous and consistent naming convention is of prime importance in this
patch.  Otherwise I think it is holding together well.

More comments tomorrow.

Thanks,
Mathieu 

>  	err = ops->load_feat(csdev, feat_csdev);
>  	if (err)
>  		return err;
>  
> -	/* add to internal csdev feature list */
> +	/* add to internal csdev feature list & initialise using reset call */
>  	mutex_lock(&cscfg_csdev_mutex);
>  	list_add(&feat_csdev->node, &csdev->feature_csdev_list);
> +	cscfg_reset_feat(feat_csdev);
>  	mutex_unlock(&cscfg_csdev_mutex);
>  
>  	return 0;
> -- 
> 2.17.1
> 
> 
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