Re: [PATCH v6 2/4] Add debugfs based silicon debug support in DWC

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Feb 14, 2025 at 04:20:05PM +0530, Shradha Todi wrote:
> Add support to provide silicon debug interface to userspace. This set
> of debug registers are part of the RASDES feature present in DesignWare
> PCIe controllers.
> 
> Signed-off-by: Shradha Todi <shradha.t@samsung.com>
> ---
>  Documentation/ABI/testing/debugfs-dwc-pcie    |  13 ++
>  drivers/pci/controller/dwc/Kconfig            |  10 +
>  drivers/pci/controller/dwc/Makefile           |   1 +
>  .../controller/dwc/pcie-designware-debugfs.c  | 207 ++++++++++++++++++
>  .../pci/controller/dwc/pcie-designware-ep.c   |   5 +
>  .../pci/controller/dwc/pcie-designware-host.c |   6 +
>  drivers/pci/controller/dwc/pcie-designware.h  |  20 ++
>  7 files changed, 262 insertions(+)
>  create mode 100644 Documentation/ABI/testing/debugfs-dwc-pcie
>  create mode 100644 drivers/pci/controller/dwc/pcie-designware-debugfs.c
> 
> diff --git a/Documentation/ABI/testing/debugfs-dwc-pcie b/Documentation/ABI/testing/debugfs-dwc-pcie
> new file mode 100644
> index 000000000000..e8ed34e988ef
> --- /dev/null
> +++ b/Documentation/ABI/testing/debugfs-dwc-pcie
> @@ -0,0 +1,13 @@
> +What:		/sys/kernel/debug/dwc_pcie_<dev>/rasdes_debug/lane_detect
> +Date:		Feburary 2025

Please align these fields

> +Contact:	Shradha Todi <shradha.t@samsung.com>
> +Description:	(RW) Write the lane number to be checked for detection.	Read
> +		will return whether PHY indicates receiver detection on the
> +		selected lane. The default selected lane is Lane0.
> +
> +What:		/sys/kernel/debug/dwc_pcie_<dev>/rasdes_debug/rx_valid
> +Date:		Feburary 2025
> +Contact:	Shradha Todi <shradha.t@samsung.com>
> +Description:	(RW) Write the lane number to be checked as valid or invalid. Read
> +		will return the status of PIPE RXVALID signal of the selected lane.
> +		The default selected lane is Lane0.
> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
> index b6d6778b0698..48a10428a492 100644
> --- a/drivers/pci/controller/dwc/Kconfig
> +++ b/drivers/pci/controller/dwc/Kconfig
> @@ -6,6 +6,16 @@ menu "DesignWare-based PCIe controllers"
>  config PCIE_DW
>  	bool
>  
> +config PCIE_DW_DEBUGFS
> +	default y
> +	depends on DEBUG_FS
> +	depends on PCIE_DW_HOST || PCIE_DW_EP
> +	bool "DWC PCIe debugfs entries"
> +	help
> +	  Enables debugfs entries for the DW PCIe Controller. These entries
> +	  provide all debug features related to DW controller including the RAS
> +	  DES features to help in debug, error injection and statistical counters.
> +
>  config PCIE_DW_HOST
>  	bool
>  	select PCIE_DW
> diff --git a/drivers/pci/controller/dwc/Makefile b/drivers/pci/controller/dwc/Makefile
> index a8308d9ea986..54565eedc52c 100644
> --- a/drivers/pci/controller/dwc/Makefile
> +++ b/drivers/pci/controller/dwc/Makefile
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_PCIE_DW) += pcie-designware.o
> +obj-$(CONFIG_PCIE_DW_DEBUGFS) += pcie-designware-debugfs.o
>  obj-$(CONFIG_PCIE_DW_HOST) += pcie-designware-host.o
>  obj-$(CONFIG_PCIE_DW_EP) += pcie-designware-ep.o
>  obj-$(CONFIG_PCIE_DW_PLAT) += pcie-designware-plat.o
> diff --git a/drivers/pci/controller/dwc/pcie-designware-debugfs.c b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
> new file mode 100644
> index 000000000000..fe799d36fa7f
> --- /dev/null
> +++ b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
> @@ -0,0 +1,207 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Synopsys DesignWare PCIe controller debugfs driver
> + *
> + * Copyright (C) 2025 Samsung Electronics Co., Ltd.
> + *		http://www.samsung.com
> + *
> + * Author: Shradha Todi <shradha.t@samsung.com>
> + */
> +
> +#include <linux/debugfs.h>
> +
> +#include "pcie-designware.h"
> +
> +#define SD_STATUS_L1LANE_REG		0xb0
> +#define PIPE_RXVALID			BIT(18)
> +#define PIPE_DETECT_LANE		BIT(17)
> +#define LANE_SELECT			GENMASK(3, 0)
> +
> +#define DWC_DEBUGFS_BUF_MAX		128
> +
> +struct dwc_pcie_vsec_id {
> +	u16 vendor_id;
> +	u16 vsec_id;
> +	u8 vsec_rev;
> +};
> +
> +/*
> + * VSEC IDs are allocated by the vendor, so a given ID may mean different
> + * things to different vendors. See PCIe r6.0, sec 7.9.5.2.
> + */
> +static const struct dwc_pcie_vsec_id dwc_pcie_vsec_ids[] = {
> +	{ .vendor_id = PCI_VENDOR_ID_ALIBABA,
> +		.vsec_id = 0x02, .vsec_rev = 0x4 },
> +	{ .vendor_id = PCI_VENDOR_ID_AMPERE,
> +		.vsec_id = 0x02, .vsec_rev = 0x4 },
> +	{ .vendor_id = PCI_VENDOR_ID_QCOM,
> +		.vsec_id = 0x02, .vsec_rev = 0x4 },
> +	{ .vendor_id = PCI_VENDOR_ID_SAMSUNG,
> +		.vsec_id = 0x02, .vsec_rev = 0x4 },
> +	{} /* terminator */

This should go into the common include file as I proposed in my series:
https://lore.kernel.org/linux-pci/20250218-pcie-qcom-ptm-v1-1-16d7e480d73e@linaro.org/

> +};
> +
> +/**
> + * struct dwc_pcie_rasdes_info - Stores controller common information
> + * @ras_cap_offset: RAS DES vendor specific extended capability offset
> + * @reg_lock: Mutex used for RASDES shadow event registers

If this is not used by all register accesses, please rename it as such. Like,
reg_event_lock.

> + *
> + * Any parameter constant to all files of the debugfs hierarchy for a single controller
> + * will be stored in this struct. It is allocated and assigned to controller specific
> + * struct dw_pcie during initialization.
> + */
> +struct dwc_pcie_rasdes_info {
> +	u32 ras_cap_offset;
> +	struct mutex reg_lock;
> +};
> +
> +static ssize_t lane_detect_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> +{
> +	struct dw_pcie *pci = file->private_data;
> +	struct dwc_pcie_rasdes_info *rinfo = pci->debugfs->rasdes_info;
> +	char debugfs_buf[DWC_DEBUGFS_BUF_MAX];
> +	ssize_t off = 0;

Not required. See below.

> +	u32 val;
> +
> +	val = dw_pcie_readl_dbi(pci, rinfo->ras_cap_offset + SD_STATUS_L1LANE_REG);
> +	val = FIELD_GET(PIPE_DETECT_LANE, val);
> +	if (val)
> +		off += scnprintf(debugfs_buf, DWC_DEBUGFS_BUF_MAX - off, "Lane Detected\n");

I don't understand why you want to add 'off' which was initialized to 0. Also
this just prints single string.

> +	else
> +		off += scnprintf(debugfs_buf, DWC_DEBUGFS_BUF_MAX - off, "Lane Undetected\n");
> +
> +	return simple_read_from_buffer(buf, count, ppos, debugfs_buf, off);
> +}
> +
> +static ssize_t lane_detect_write(struct file *file, const char __user *buf,
> +				 size_t count, loff_t *ppos)
> +{
> +	struct dw_pcie *pci = file->private_data;
> +	struct dwc_pcie_rasdes_info *rinfo = pci->debugfs->rasdes_info;
> +	u32 lane, val;
> +
> +	val = kstrtou32_from_user(buf, count, 0, &lane);
> +	if (val)
> +		return val;
> +
> +	val = dw_pcie_readl_dbi(pci, rinfo->ras_cap_offset + SD_STATUS_L1LANE_REG);
> +	val &= ~(LANE_SELECT);
> +	val |= FIELD_PREP(LANE_SELECT, lane);
> +	dw_pcie_writel_dbi(pci, rinfo->ras_cap_offset + SD_STATUS_L1LANE_REG, val);
> +
> +	return count;
> +}
> +
> +static ssize_t rx_valid_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> +{
> +	struct dw_pcie *pci = file->private_data;
> +	struct dwc_pcie_rasdes_info *rinfo = pci->debugfs->rasdes_info;
> +	char debugfs_buf[DWC_DEBUGFS_BUF_MAX];
> +	ssize_t off = 0;
> +	u32 val;
> +
> +	val = dw_pcie_readl_dbi(pci, rinfo->ras_cap_offset + SD_STATUS_L1LANE_REG);
> +	val = FIELD_GET(PIPE_RXVALID, val);
> +	if (val)
> +		off += scnprintf(debugfs_buf, DWC_DEBUGFS_BUF_MAX - off, "RX Valid\n");

Same here.

> +	else
> +		off += scnprintf(debugfs_buf, DWC_DEBUGFS_BUF_MAX - off, "RX Invalid\n");
> +
> +	return simple_read_from_buffer(buf, count, ppos, debugfs_buf, off);
> +}
> +
> +static ssize_t rx_valid_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
> +{
> +	return lane_detect_write(file, buf, count, ppos);
> +}
> +
> +#define dwc_debugfs_create(name)			\
> +debugfs_create_file(#name, 0644, rasdes_debug, pci,	\
> +			&dbg_ ## name ## _fops)
> +
> +#define DWC_DEBUGFS_FOPS(name)					\
> +static const struct file_operations dbg_ ## name ## _fops = {	\
> +	.open = simple_open,				\
> +	.read = name ## _read,				\
> +	.write = name ## _write				\
> +}
> +
> +DWC_DEBUGFS_FOPS(lane_detect);
> +DWC_DEBUGFS_FOPS(rx_valid);
> +
> +static void dwc_pcie_rasdes_debugfs_deinit(struct dw_pcie *pci)
> +{
> +	struct dwc_pcie_rasdes_info *rinfo = pci->debugfs->rasdes_info;
> +
> +	mutex_destroy(&rinfo->reg_lock);
> +}
> +
> +static int dwc_pcie_rasdes_debugfs_init(struct dw_pcie *pci, struct dentry *dir)
> +{
> +	struct dentry *rasdes_debug;
> +	struct dwc_pcie_rasdes_info *rasdes_info;
> +	const struct dwc_pcie_vsec_id *vid;
> +	struct device *dev = pci->dev;
> +	int ras_cap;
> +
> +	for (vid = dwc_pcie_vsec_ids; vid->vendor_id; vid++) {
> +		ras_cap = dw_pcie_find_vsec_capability(pci, vid->vendor_id,
> +							vid->vsec_id);
> +		if (ras_cap)
> +			break;
> +	}
> +	if (!ras_cap) {
> +		dev_dbg(dev, "no rasdes capability available\n");
> +		return -ENODEV;
> +	}

This will also go inside a new API, dw_pcie_find_rasdes_capability(pci).

> +
> +	rasdes_info = devm_kzalloc(dev, sizeof(*rasdes_info), GFP_KERNEL);
> +	if (!rasdes_info)
> +		return -ENOMEM;
> +
> +	/* Create subdirectories for Debug, Error injection, Statistics */
> +	rasdes_debug = debugfs_create_dir("rasdes_debug", dir);

_debug prefix is not needed since the directory itself belongs to debugfs.

> +
> +	mutex_init(&rasdes_info->reg_lock);
> +	rasdes_info->ras_cap_offset = ras_cap;
> +	pci->debugfs->rasdes_info = rasdes_info;
> +
> +	/* Create debugfs files for Debug subdirectory */
> +	dwc_debugfs_create(lane_detect);
> +	dwc_debugfs_create(rx_valid);
> +
> +	return 0;
> +}
> +
> +void dwc_pcie_debugfs_deinit(struct dw_pcie *pci)
> +{
> +	dwc_pcie_rasdes_debugfs_deinit(pci);
> +	debugfs_remove_recursive(pci->debugfs->debug_dir);
> +}
> +
> +int dwc_pcie_debugfs_init(struct dw_pcie *pci)
> +{
> +	char dirname[DWC_DEBUGFS_BUF_MAX];
> +	struct device *dev = pci->dev;
> +	struct debugfs_info *debugfs;
> +	struct dentry *dir;
> +	int ret;
> +
> +	/* Create main directory for each platform driver */
> +	snprintf(dirname, DWC_DEBUGFS_BUF_MAX, "dwc_pcie_%s", dev_name(dev));
> +	dir = debugfs_create_dir(dirname, NULL);
> +	if (IS_ERR(dir))
> +		return PTR_ERR(dir);

debugfs creation is not supposed to fail. So you should remove the error check.

> +
> +	debugfs = devm_kzalloc(dev, sizeof(*debugfs), GFP_KERNEL);
> +	if (!debugfs)
> +		return -ENOMEM;
> +
> +	debugfs->debug_dir = dir;
> +	pci->debugfs = debugfs;
> +	ret = dwc_pcie_rasdes_debugfs_init(pci, dir);
> +	if (ret)
> +		dev_dbg(dev, "rasdes debugfs init failed\n");

RASDES

> +
> +	return 0;
> +}
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index f3ac7d46a855..a87a714bb472 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -642,6 +642,7 @@ void dw_pcie_ep_cleanup(struct dw_pcie_ep *ep)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  
> +	dwc_pcie_debugfs_deinit(pci);
>  	dw_pcie_edma_remove(pci);
>  }
>  EXPORT_SYMBOL_GPL(dw_pcie_ep_cleanup);
> @@ -813,6 +814,10 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
>  
>  	dw_pcie_ep_init_non_sticky_registers(pci);
>  
> +	ret = dwc_pcie_debugfs_init(pci);
> +	if (ret)
> +		goto err_remove_edma;
> +
>  	return 0;
>  
>  err_remove_edma:
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index d2291c3ceb8b..6b03ef7fd014 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -524,6 +524,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
>  	if (ret)
>  		goto err_remove_edma;
>  
> +	ret = dwc_pcie_debugfs_init(pci);
> +	if (ret)
> +		goto err_remove_edma;
> +

Why can't you move it to the end of the function?

>  	if (!dw_pcie_link_up(pci)) {
>  		ret = dw_pcie_start_link(pci);
>  		if (ret)
> @@ -571,6 +575,8 @@ void dw_pcie_host_deinit(struct dw_pcie_rp *pp)
>  
>  	dw_pcie_stop_link(pci);
>  
> +	dwc_pcie_debugfs_deinit(pci);
> +

This should be moved to the start of the function.

- Mani

-- 
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