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Date:   Mon, 7 Nov 2022 14:30:48 +0000
From:   Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To:     Junhao He <hejunhao3@huawei.com>
CC:     <mathieu.poirier@linaro.org>, <suzuki.poulose@arm.com>,
        <mike.leach@linaro.org>, <leo.yan@linaro.org>,
        <john.garry@huawei.com>, <coresight@lists.linaro.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>, <linuxarm@huawei.com>,
        <rdunlap@infradead.org>, <liuqi115@huawei.com>,
        <f.fangjian@huawei.com>, <prime.zeng@hisilicon.com>,
        <yangyicong@huawei.com>, <shenyang39@huawei.com>
Subject: Re: [PATCH v11 1/2] drivers/coresight: Add UltraSoc System Memory
 Buffer driver
Message-ID: <20221107143048.00004da2@Huawei.com>
In-Reply-To: <20221107130624.59886-2-hejunhao3@huawei.com>
References: <20221107130624.59886-1-hejunhao3@huawei.com>
        <20221107130624.59886-2-hejunhao3@huawei.com>
Organization: Huawei Technologies Research and Development (UK) Ltd.
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On Mon, 7 Nov 2022 21:06:23 +0800
Junhao He <hejunhao3@huawei.com> wrote:

> From: Qi Liu <liuqi115@huawei.com>
> 
> This patch adds driver for UltraSoc SMB(System Memory Buffer)
> device. SMB provides a way to buffer messages from ETM, and
> store these "CPU instructions trace" in system memory.
> 
> SMB is developed by UltraSoc technology, which is acquired by
> Siemens, and we still use "UltraSoc" to name driver.
> 
> Signed-off-by: Qi Liu <liuqi115@huawei.com>
> Signed-off-by: Junhao He <hejunhao3@huawei.com>
> Tested-by: JunHao He <hejunhao3@huawei.com>

Hi JunHao,

It's been a while since I last looked at this driver, so I may have
forgotten or missed previous discussions.

All the comments inline are fairly superficial and mostly concerned
with making the code easy to review / maintain rather than correctness.

Jonathan


> ---
>  drivers/hwtracing/coresight/Kconfig        |  11 +
>  drivers/hwtracing/coresight/Makefile       |   1 +
>  drivers/hwtracing/coresight/ultrasoc-smb.c | 631 +++++++++++++++++++++
>  drivers/hwtracing/coresight/ultrasoc-smb.h | 113 ++++
>  4 files changed, 756 insertions(+)
>  create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.c
>  create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.h
> 
> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
> index 45c1eb5dfcb7..05d791cb05e3 100644
> --- a/drivers/hwtracing/coresight/Kconfig
> +++ b/drivers/hwtracing/coresight/Kconfig
> @@ -201,4 +201,15 @@ config CORESIGHT_TRBE
>  
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called coresight-trbe.
> +
> +config ULTRASOC_SMB
> +	tristate "Ultrasoc system memory buffer drivers"
> +	depends on ACPI && ARM64 && CORESIGHT_LINKS_AND_SINKS

Can you relax this at all in the interests of getting better CI build coverage
from random configs etc. 

From a quick look, I think you can safely drop the ACPI dependency on basis
relevant functions are stubbed out in acpi.h

However, it looks like coresight more generally uses such depends, so perhaps
better to just leave them here for consistency.

> +	help
> +	  This driver provides support for the Ultrasoc system memory buffer (SMB).
> +	  SMB is responsible for receiving the trace data from Coresight ETM devices
> +	  and storing them to a system buffer.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called ultrasoc-smb.
>  endif


> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
> new file mode 100644
> index 000000000000..7fe8bf9623e8
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
> @@ -0,0 +1,631 @@

...


> +
> +static void smb_buffer_sync_status(struct smb_drv_data *drvdata)
> +{
> +	struct smb_data_buffer *sdb = &drvdata->sdb;
> +
> +	sdb->wr_offset = readl(drvdata->base + SMB_LB_WR_ADDR) - sdb->start_addr;
> +	sdb->rd_offset = readl(drvdata->base + SMB_LB_RD_ADDR) - sdb->start_addr;
> +	if (sdb->wr_offset == sdb->rd_offset && !smb_buffer_is_empty(drvdata))
> +		sdb->full = true;
> +	else
> +		sdb->full = false;

Could do as
	sdb->full = sdb->wr_offset == sdb->rd_offset && !smb_buffer_is_empty(drvdata);
up to you on which you think is more readable.

> +}
> +


> +static struct attribute *smb_sink_attrs[] = {
> +	coresight_simple_reg32(read_pos, SMB_LB_RD_ADDR),
> +	coresight_simple_reg32(write_pos, SMB_LB_WR_ADDR),
> +	coresight_simple_reg32(buf_status, SMB_LB_INT_STS),
> +	&dev_attr_buf_size.attr,
> +	NULL,
As below.

> +};
> +
> +static const struct attribute_group smb_sink_group = {
> +	.attrs = smb_sink_attrs,
> +	.name = "mgmt",
> +};
> +
> +static const struct attribute_group *smb_sink_groups[] = {
> +	&smb_sink_group,
> +	NULL,

Generally no comma after a NULL terminator.  Having a comma
implies it may make sense to put something after it, which is never
the case for these.

> +};
> +


...

> +static void smb_sync_perf_buffer(struct smb_drv_data *drvdata,
> +				 struct cs_buffers *buf,
> +				 unsigned long head,
> +				 unsigned long data_size)
> +{
> +	struct smb_data_buffer *sdb = &drvdata->sdb;
> +	char **dst_pages = (char **)buf->data_pages;

Do you need the cast?  It's void ** so implicit cast should work I think.
	char **dst_pages = buf->data_pages;

> +	unsigned long to_copy;
> +	long pg_idx, pg_offset;
> +
> +	pg_idx = head >> PAGE_SHIFT;
> +	pg_offset = head & (PAGE_SIZE - 1);
> +
> +	while (data_size) {
> +		unsigned long pg_space = PAGE_SIZE - pg_offset;
> +
> +		/* Copy parts of trace data when read pointer wrap around */
> +		if (sdb->rd_offset + pg_space > sdb->buf_size)
> +			to_copy = sdb->buf_size - sdb->rd_offset;
> +		else
> +			to_copy = min(data_size, pg_space);
> +
> +		memcpy(dst_pages[pg_idx] + pg_offset,
> +			      sdb->buf_base + sdb->rd_offset, to_copy);
> +
> +		pg_offset += to_copy;
> +		if (pg_offset >= PAGE_SIZE) {
> +			pg_offset = 0;
> +			pg_idx++;
> +			pg_idx %= buf->nr_pages;
> +		}
> +		data_size -= to_copy;
> +		sdb->rd_offset += to_copy;
> +		sdb->rd_offset %= sdb->buf_size;
> +	}
> +
> +	sdb->data_size = 0;
> +	writel(sdb->start_addr + sdb->rd_offset, drvdata->base + SMB_LB_RD_ADDR);
> +
> +	/*
> +	 * Data remained in link cannot be purged when SMB is full, so
> +	 * synchronize the read pointer to write pointer, to make sure
> +	 * these remained data won't influence next trace.
> +	 */
> +	if (sdb->full) {
> +		smb_purge_data(drvdata);
> +		writel(readl(drvdata->base + SMB_LB_WR_ADDR),
> +		       drvdata->base + SMB_LB_RD_ADDR);
> +	}
> +	smb_reset_buffer_status(drvdata);
> +}


...

> +
> +static void smb_init_hw(struct smb_drv_data *drvdata)
> +{
> +	/* First disable smb and clear the status of SMB buffer */

Check for consistency in capitalization of SMB in all comments.

> +	smb_reset_buffer_status(drvdata);
> +	smb_disable_hw(drvdata);
> +	smb_purge_data(drvdata);
> +
> +	writel(SMB_BUF_CFG_STREAMING, drvdata->base + SMB_LB_CFG_LO);
> +	writel(SMB_MSG_FILTER, drvdata->base + SMB_LB_CFG_HI);
> +	writel(SMB_GLOBAL_CFG, drvdata->base + SMB_CFG_REG);
> +	writel(SMB_GLB_INT_CFG, drvdata->base + SMB_GLOBAL_INT);
> +	writel(SMB_BUF_INT_CFG, drvdata->base + SMB_LB_INT_CTRL);
> +}
> +


...

> +static int smb_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct smb_drv_data *drvdata;
> +	int ret;
> +
> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> +	if (!drvdata)
> +		return -ENOMEM;
> +
> +	drvdata->base = devm_platform_ioremap_resource(pdev, SMB_BASE_ADDR_RES);
> +	if (IS_ERR(drvdata->base)) {
> +		dev_err(dev, "Failed to ioremap resource\n");
> +		return PTR_ERR(drvdata->base);
> +	}
> +
> +	ret = smb_init_data_buffer(pdev, &drvdata->sdb);
> +	if (ret) {
> +		dev_err(dev, "Failed to init buffer, ret = %d\n", ret);
> +		return ret;
> +	}
> +
> +	smb_init_hw(drvdata);
> +	mutex_init(&drvdata->mutex);
> +	drvdata->pid = -1;
> +
> +	ret = smb_register_sink(pdev, drvdata);
> +	if (ret) {
> +		dev_err(dev, "Failed to register smb sink\n");
> +		return ret;
> +	}
> +
> +	ret = smb_config_inport(dev, true);
> +	if (ret) {
> +		smb_unregister_sink(drvdata);
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, drvdata);
> +	return 0;
> +}
> +
> +static int smb_remove(struct platform_device *pdev)
> +{
> +	struct smb_drv_data *drvdata = platform_get_drvdata(pdev);
> +	int ret;
> +
> +	ret = smb_config_inport(&pdev->dev, false);
> +	if (ret)
> +		return ret;
> +
> +	smb_unregister_sink(drvdata);

Trivial: I find a blank line before plane returns like this helps
a little with readability.  Up to you though!

> +	return 0;
> +}
> +
> +static const struct acpi_device_id ultrasoc_smb_acpi_match[] = {
> +	{"HISI03A1", 0},
> +	{},
Trivial, but little point in a trailing comma on a NULL terminator.

	{}
};

is normally fine - note this is a bit subsystem specific so maintainer
may say otherwise.

> +};
> +MODULE_DEVICE_TABLE(acpi, ultrasoc_smb_acpi_match);
> +
> +static struct platform_driver smb_driver = {
> +	.driver = {
> +		.name = "ultrasoc-smb",
> +		.acpi_match_table = ACPI_PTR(ultrasoc_smb_acpi_match),
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe = smb_probe,
> +	.remove = smb_remove,
> +};
> +module_platform_driver(smb_driver);
> +
> +MODULE_DESCRIPTION("UltraSoc SMB CoreSight driver");
> +MODULE_LICENSE("Dual MIT/GPL");
> +MODULE_AUTHOR("Jonathan Zhou <jonathan.zhouwen@huawei.com>");
> +MODULE_AUTHOR("Qi Liu <liuqi115@huawei.com>");
> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h
> new file mode 100644
> index 000000000000..56170e1a883d
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.h
> @@ -0,0 +1,113 @@
> +/* SPDX-License-Identifier: (GPL-2.0 OR MIT) */
> +/*
> + * Siemens System Memory Buffer driver.
> + * Copyright(c) 2022, HiSilicon Limited.
> + */
> +
> +#ifndef _ULTRASOC_SMB_H
> +#define _ULTRASOC_SMB_H
> +
> +#include <linux/coresight.h>
I think you could move this down into the c files and provide
a forwards definition of struct coresight device

Always good to keep scope of includes to minimum necessary.

> +#include <linux/miscdevice.h>
> +#include <linux/mutex.h>
> +
> +/* Offset of SMB logical buffer registers */
> +#define SMB_CFG_REG		0x00

To avoid any naming confusion I would postfix all the register
addresses with _REG
Then rethink the naming so the field names make it clear which
register they are in.

> +#define SMB_GLOBAL_EN		0x04
> +#define SMB_GLOBAL_INT		0x08
> +#define SMB_LB_CFG_LO		0x40
> +#define SMB_LB_CFG_HI		0x44
> +#define SMB_LB_INT_CTRL		0x48
> +#define SMB_LB_INT_STS		0x4c
> +#define SMB_LB_LIMIT		0x58
> +#define SMB_LB_RD_ADDR		0x5c
> +#define SMB_LB_WR_ADDR		0x60
> +#define SMB_LB_PURGE		0x64
> +
> +/* Set SMB_CFG_REG register */
> +#define SMB_BURST_LEN		GENMASK(7, 4)
> +#define SMB_IDLE_PRD		GENMASK(15, 12)
> +#define SMB_MEM_WR		GENMASK(17, 16)
> +#define SMB_MEM_RD		(GENMASK(26, 25) | GENMASK(23, 22))

Are these masks, or default values? Ideally express them as
a field mask then the value via FIELD_PREP

e.g.
#define SMB_CFG_BURST_LEN_MSK GENMASK(7, 4)
#define SMB_GLOBAL_CFG_DEFAULT    ... | FIELD_PREP(SMB_CFG_BURST_LEN_MSK, 0xf) | etc

 
> +#define SMB_GLOBAL_CFG		(SMB_IDLE_PRD |	SMB_MEM_WR | SMB_MEM_RD | \
> +				 SMB_BURST_LEN)
> +
> +/* Set SMB_GLOBAL_INT register */
> +#define SMB_INT_EN		BIT(0)
> +#define SMB_INT_TYPE_PULSE	BIT(1)
> +#define SMB_INT_POLARITY_HIGH	BIT(2)
> +#define SMB_GLB_INT_CFG		(SMB_INT_EN | SMB_INT_TYPE_PULSE |	\
> +				 SMB_INT_POLARITY_HIGH)
> +
> +/* Set SMB_LB_CFG_LO register */
> +#define SMB_BUF_EN		BIT(0)
> +#define SMB_BUF_SINGLE_END	BIT(1)
> +#define SMB_BUF_INIT		BIT(8)
> +#define SMB_BUF_CONTINUOUS	BIT(11)
> +#define SMB_FILTER_FLOW		GENMASK(19, 16)
> +#define SMB_BUF_CFG_STREAMING	(SMB_BUF_INIT | SMB_BUF_CONTINUOUS |	\
> +				 SMB_FILTER_FLOW | SMB_BUF_SINGLE_END |	\
> +				 SMB_BUF_EN)
> +
> +#define SMB_BASE_LOW_MASK	GENMASK(31, 0)
> +
> +/* Set SMB_LB_CFG_HI register */
> +#define SMB_MSG_FILTER		GENMASK(15, 8)
> +
> +/* Set SMB_LB_INT_CTRL */
> +#define SMB_BUF_INT_EN		BIT(0)
> +#define SMB_BUF_NOTE_MASK	GENMASK(11, 8)
> +#define SMB_BUF_INT_CFG		(SMB_BUF_INT_EN | SMB_BUF_NOTE_MASK)
> +
> +#define SMB_BUF_NOT_EMPTY       BIT(0)
> +#define SMB_RESET_BUF_STS       GENMASK(3, 0)
> +#define SMB_PURGED              BIT(0)
> +#define SMB_HW_ENABLE           BIT(0)

It is useful to give fields names that reflect which register they are in.
Perhaps
SMB_GLOBAL_EN_HW_ENABLE for this one.

> +
> +#define SMB_BASE_ADDR_RES       0
> +#define SMB_BUF_INFO_RES        1
> +
> +/**
> + * struct smb_data_buffer - Details of the buffer used by SMB
> + * @buf_base:	Memory mapped base address of SMB.
> + * @start_addr:	SMB buffer start Physical address.
> + * @buf_size:	Size of the buffer.
> + * @data_size:	Size of Trace data copy to userspace.
> + * @rd_offset:	Offset of the read pointer in the buffer.
> + * @wr_offset:	Offset of the write pointer in the buffer.
> + * @status:	Status of SMB buffer.

Naming wrong. 

> + */
> +struct smb_data_buffer {
> +	void __iomem *buf_base;
> +	u32 start_addr;
> +	unsigned long buf_size;
> +	unsigned long data_size;
> +	unsigned long rd_offset;
> +	unsigned long wr_offset;
> +	bool full;
> +};
> +
> +/**
> + * struct smb_drv_data - specifics associated to an SMB component
> + * @base:	Memory mapped base address for SMB component.
> + * @csdev:	Component vitals needed by the framework.
> + * @sdb:	Data buffer for SMB.
> + * @miscdev:	Specifics to handle "/dev/xyz.smb" entry.
> + * @mutex:	Control data access to one at a time.
> + * @reading:	Synchronise user space access to SMB buffer.
> + * @pid:	Process ID of the process being monitored by the
> + * 		session that is using this component.
> + * @mode:	how this SMB is being used, perf mode or sysfs mode.
> + */
> +struct smb_drv_data {
> +	void __iomem *base;
> +	struct coresight_device	*csdev;
> +	struct smb_data_buffer sdb;
> +	struct miscdevice miscdev;
> +	struct mutex mutex;
> +	local_t reading;
> +	pid_t pid;
> +	u32 mode;
> +};
> +
> +#endif