[PATCH V1 0/3] Add Data Capture and Compare(DCC) driver to new location

[PATCH V1 0/3] Add Data Capture and Compare(DCC) driver to new location

[Souradeep Chowdhury]

DCC(Data Capture and Compare) is a DMA engine designed for debugging purposes.
In case of a system crash or manual software triggers by the user the DCC hardware
stores the value at the register addresses which can be used for debugging purposes.
The DCC driver provides the user with debugfs interface to configure the register
addresses. The options that the DCC hardware provides include reading from registers,
writing to registers, first reading and then writing to registers and looping
through the values of the same register.

This patch series is a continuation of the previous series

https://lore.kernel.org/linux-arm-kernel/20221228172825.r32vpphbdulaldvv@builder.lan/T/

The dcc driver is moved to a new location drivers/misc along with the binding
as per discussions.

Souradeep Chowdhury (3):
  dt-bindings: misc: qcom,dcc: Add the dtschema
  drivers: misc: dcc: Add driver support for Data Capture and Compare
    unit(DCC)
  MAINTAINERS: Add the entry for DCC(Data Capture and Compare) driver
    support

 .../devicetree/bindings/misc/qcom,dcc.yaml         |   44 +
 MAINTAINERS                                        |    8 +
 drivers/misc/Kconfig                               |    8 +
 drivers/misc/Makefile                              |    1 +
 drivers/misc/dcc.c                                 | 1305 ++++++++++++++++++++
 5 files changed, 1366 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/qcom,dcc.yaml
 create mode 100644 drivers/misc/dcc.c

--
2.7.4

[PATCH V1 1/3] dt-bindings: misc: qcom,dcc: Add the dtschema

[Souradeep Chowdhury]

Add the device tree bindings for Data Capture and Compare(DCC).

Signed-off-by: Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bjorn Andersson <andersson@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
---
 .../devicetree/bindings/misc/qcom,dcc.yaml         | 44 ++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/qcom,dcc.yaml

diff --git a/Documentation/devicetree/bindings/misc/qcom,dcc.yaml b/Documentation/devicetree/bindings/misc/qcom,dcc.yaml
new file mode 100644
index 0000000..055f3cb
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/qcom,dcc.yaml
@@ -0,0 +1,44 @@
+# SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/misc/qcom,dcc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Data Capture and Compare
+
+maintainers:
+  - Souradeep Chowdhury <quic_schowdhu@quicinc.com>
+
+description: |
+    DCC (Data Capture and Compare) is a DMA engine which is used to save
+    configuration data or system memory contents during catastrophic failure
+    or SW trigger. DCC is used to capture and store data for debugging purpose
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - qcom,sm8150-dcc
+          - qcom,sc7280-dcc
+          - qcom,sc7180-dcc
+          - qcom,sdm845-dcc
+      - const: qcom,dcc
+
+  reg:
+    items:
+      - description: DCC base
+      - description: DCC RAM base
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    dma@10a2000{
+        compatible = "qcom,sm8150-dcc", "qcom,dcc";
+        reg = <0x010a2000 0x1000>,
+              <0x010ad000 0x2000>;
+    };
-- 
2.7.4

[PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

[Souradeep Chowdhury]

The DCC is a DMA Engine designed to capture and store data
during system crash or software triggers. The DCC operates
based on user inputs via the debugfs interface. The user gives
addresses as inputs and these addresses are stored in the
dcc sram. In case of a system crash or a manual software
trigger by the user through the debugfs interface,
the dcc captures and stores the values at these addresses.
This patch contains the driver which has all the methods
pertaining to the debugfs interface, auxiliary functions to
support all the four fundamental operations of dcc namely
read, write, read/modify/write and loop. The probe method
here instantiates all the resources necessary for dcc to
operate mainly the dedicated dcc sram where it stores the
values. The DCC driver can be used for debugging purposes
without going for a reboot since it can perform software
triggers as well based on user inputs.

Also add the documentation for debugfs entries which explains
the functionalities of each debugfs file that has been created
for dcc.

The following is the justification of using debugfs interface
over the other alternatives like sysfs/ioctls

i) As can be seen from the debugfs attribute descriptions,
some of the debugfs attribute files here contains multiple
arguments which needs to be accepted from the user. This goes
against the design style of sysfs.

ii) The user input patterns have been made simple and convenient
in this case with the use of debugfs interface as user doesn't
need to shuffle between different files to execute one instruction
as was the case on using other alternatives.

Signed-off-by: Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Reviewed-by: Alex Elder <elder@linaro.org>
---
 drivers/misc/Kconfig  |    8 +
 drivers/misc/Makefile |    1 +
 drivers/misc/dcc.c    | 1305 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1314 insertions(+)
 create mode 100644 drivers/misc/dcc.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 433aa41..e2bc652 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -276,6 +276,14 @@ config QCOM_COINCELL
 	  to maintain PMIC register and RTC state in the absence of
 	  external power.
 
+config QCOM_DCC
+	tristate "Qualcomm Technologies, Inc. Data Capture and Compare(DCC) engine driver"
+	depends on ARCH_QCOM || COMPILE_TEST
+	help
+	  This option enables driver for Data Capture and Compare engine. DCC
+	  driver provides interface to configure DCC block and read back
+	  captured data from DCC's internal SRAM.
+
 config QCOM_FASTRPC
 	tristate "Qualcomm FastRPC"
 	depends on ARCH_QCOM || COMPILE_TEST
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 56de439..6fa8efa 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_TIFM_CORE)       	+= tifm_core.o
 obj-$(CONFIG_TIFM_7XX1)       	+= tifm_7xx1.o
 obj-$(CONFIG_PHANTOM)		+= phantom.o
 obj-$(CONFIG_QCOM_COINCELL)	+= qcom-coincell.o
+obj-$(CONFIG_QCOM_DCC)		+= dcc.o
 obj-$(CONFIG_QCOM_FASTRPC)	+= fastrpc.o
 obj-$(CONFIG_SENSORS_BH1770)	+= bh1770glc.o
 obj-$(CONFIG_SENSORS_APDS990X)	+= apds990x.o
diff --git a/drivers/misc/dcc.c b/drivers/misc/dcc.c
new file mode 100644
index 0000000..69973ea
--- /dev/null
+++ b/drivers/misc/dcc.c
@@ -0,0 +1,1305 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2022, Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#define STATUS_READY_TIMEOUT		5000  /* microseconds */
+
+#define DCC_SRAM_NODE "dcc_sram"
+
+/* DCC registers */
+#define DCC_HW_INFO			0x04
+#define DCC_LL_NUM_INFO			0x10
+#define DCC_STATUS(vers)		((vers) == 1 ? 0x0c : 0x1c)
+#define DCC_LL_LOCK			0x00
+#define DCC_LL_CFG			0x04
+#define DCC_LL_BASE			0x08
+#define DCC_FD_BASE			0x0c
+#define DCC_LL_TIMEOUT			0x10
+#define DCC_LL_INT_ENABLE		0x18
+#define DCC_LL_INT_STATUS		0x1c
+#define DCC_LL_SW_TRIGGER		0x2c
+#define DCC_LL_BUS_ACCESS_STATUS	0x30
+
+/* Default value used if a bit 6 in the HW_INFO register is set. */
+#define DCC_FIX_LOOP_OFFSET		16
+
+/* Mask to find version info from HW_Info register */
+#define DCC_VER_INFO_MASK		BIT(9)
+
+#define MAX_DCC_OFFSET			GENMASK(9, 2)
+#define MAX_DCC_LEN			GENMASK(6, 0)
+#define MAX_LOOP_CNT			GENMASK(7, 0)
+#define MAX_LOOP_ADDR			10
+
+#define DCC_ADDR_DESCRIPTOR		0x00
+#define DCC_ADDR_LIMIT			27
+#define DCC_WORD_SIZE			sizeof(u32)
+#define DCC_ADDR_RANGE_MASK		GENMASK(31, 4)
+#define DCC_LOOP_DESCRIPTOR		BIT(30)
+#define DCC_RD_MOD_WR_DESCRIPTOR	BIT(31)
+#define DCC_LINK_DESCRIPTOR		GENMASK(31, 30)
+#define DCC_STATUS_MASK			GENMASK(1, 0)
+#define DCC_LOCK_MASK			BIT(0)
+#define DCC_LOOP_OFFSET_MASK		BIT(6)
+#define DCC_TRIGGER_MASK		BIT(9)
+
+#define DCC_WRITE_MASK			BIT(15)
+#define DCC_WRITE_OFF_MASK		GENMASK(7, 0)
+#define DCC_WRITE_LEN_MASK		GENMASK(14, 8)
+
+#define DCC_READ_IND			0x00
+#define DCC_WRITE_IND			(BIT(28))
+
+#define DCC_AHB_IND			0x00
+#define DCC_APB_IND			BIT(29)
+
+#define DCC_MAX_LINK_LIST		8
+
+#define DCC_VER_MASK2			GENMASK(5, 0)
+
+#define DCC_SRAM_WORD_LENGTH		4
+
+#define DCC_RD_MOD_WR_ADDR              0xC105E
+
+enum dcc_descriptor_type {
+	DCC_READ_TYPE,
+	DCC_LOOP_TYPE,
+	DCC_READ_WRITE_TYPE,
+	DCC_WRITE_TYPE
+};
+
+struct dcc_config_entry {
+	u32				base;
+	u32				offset;
+	u32				len;
+	u32				loop_cnt;
+	u32				write_val;
+	u32				mask;
+	bool				apb_bus;
+	enum dcc_descriptor_type	desc_type;
+	struct list_head		list;
+};
+
+/**
+ * struct dcc_drvdata - configuration information related to a dcc device
+ * @base:		Base Address of the dcc device
+ * @dev:		The device attached to the driver data
+ * @mutex:		Lock to protect access and manipulation of dcc_drvdata
+ * @ram_base:		Base address for the SRAM dedicated for the dcc device
+ * @ram_size:		Total size of the SRAM dedicated for the dcc device
+ * @ram_offset:		Offset to the SRAM dedicated for dcc device
+ * @mem_map_ver:	Memory map version of DCC hardware
+ * @ram_cfg:		Used for address limit calculation for dcc
+ * @ram_start:		Starting address of DCC SRAM
+ * @sram_dev:		Miscellaneous device equivalent of dcc SRAM
+ * @cfg_head:		Points to the head of the linked list of addresses
+ * @dbg_dir:		The dcc debugfs directory under which all the debugfs files are placed
+ * @nr_link_list:	Total number of linkedlists supported by the DCC configuration
+ * @loop_shift:		Loop offset bits range for the addresses
+ * @enable_bitmap:	Bitmap to capture the enabled status of each linked list of addresses
+ */
+struct dcc_drvdata {
+	void __iomem		*base;
+	void __iomem            *ram_base;
+	struct device		*dev;
+	struct mutex		mutex;
+	size_t			ram_size;
+	size_t			ram_offset;
+	int			mem_map_ver;
+	unsigned int		ram_cfg;
+	unsigned int		ram_start;
+	struct miscdevice	sram_dev;
+	struct list_head	*cfg_head;
+	struct dentry		*dbg_dir;
+	size_t			nr_link_list;
+	u8			loop_shift;
+	unsigned long		*enable_bitmap;
+};
+
+struct dcc_cfg_attr {
+	u32	addr;
+	u32	prev_addr;
+	u32	prev_off;
+	u32	link;
+	u32	sram_offset;
+};
+
+struct dcc_cfg_loop_attr {
+	u32	loop_cnt;
+	u32	loop_len;
+	u32	loop_off;
+	bool    loop_start;
+};
+
+static inline u32 dcc_list_offset(int version)
+{
+	return version == 1 ? 0x1c : version == 2 ? 0x2c : 0x34;
+}
+
+static inline void dcc_list_writel(struct dcc_drvdata *drvdata,
+				   u32 ll, u32 val, u32 off)
+{
+	u32 offset = dcc_list_offset(drvdata->mem_map_ver) + off;
+
+	writel(val, drvdata->base + ll * 0x80 + offset);
+}
+
+static inline u32 dcc_list_readl(struct dcc_drvdata *drvdata, u32 ll, u32 off)
+{
+	u32 offset = dcc_list_offset(drvdata->mem_map_ver) + off;
+
+	return readl(drvdata->base + ll * 0x80 + offset);
+}
+
+static void dcc_sram_write_auto(struct dcc_drvdata *drvdata,
+				u32 val, u32 *off)
+{
+	/* If the overflow condition is met increment the offset
+	 * and return to indicate that overflow has occurred
+	 */
+	if (unlikely(*off > drvdata->ram_size - 4)) {
+		*off += 4;
+		return;
+	}
+
+	writel(val, drvdata->ram_base + *off);
+
+	*off += 4;
+}
+
+static int dcc_sw_trigger(struct dcc_drvdata *drvdata)
+{
+	void __iomem *addr;
+	int ret;
+	int i;
+	u32 status;
+	u32 ll_cfg;
+	u32 tmp_ll_cfg;
+	u32 val;
+
+	mutex_lock(&drvdata->mutex);
+
+	for (i = 0; i < drvdata->nr_link_list; i++) {
+		if (!test_bit(i, drvdata->enable_bitmap))
+			continue;
+		ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
+		tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
+		dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
+		dcc_list_writel(drvdata, 1, i, DCC_LL_SW_TRIGGER);
+		dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
+	}
+
+	addr = drvdata->base + DCC_STATUS(drvdata->mem_map_ver);
+	if (readl_poll_timeout(addr, val, !FIELD_GET(DCC_STATUS_MASK, val),
+			       1, STATUS_READY_TIMEOUT)) {
+		dev_err(drvdata->dev, "DCC is busy after receiving sw trigger\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
+	for (i = 0; i < drvdata->nr_link_list; i++) {
+		if (!test_bit(i, drvdata->enable_bitmap))
+			continue;
+
+		status = dcc_list_readl(drvdata, i, DCC_LL_BUS_ACCESS_STATUS);
+		if (!status)
+			continue;
+
+		dev_err(drvdata->dev, "Read access error for list %d err: 0x%x\n",
+			i, status);
+		ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
+		tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
+		dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
+		dcc_list_writel(drvdata, DCC_STATUS_MASK, i, DCC_LL_BUS_ACCESS_STATUS);
+		dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
+		ret = -ENODATA;
+		break;
+	}
+
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+	return ret;
+}
+
+static void dcc_ll_cfg_reset_link(struct dcc_cfg_attr *cfg)
+{
+	cfg->addr = 0x00;
+	cfg->link = 0;
+	cfg->prev_off = 0;
+	cfg->prev_addr = cfg->addr;
+}
+
+static void dcc_emit_read_write(struct dcc_drvdata *drvdata,
+				struct dcc_config_entry *entry,
+				struct dcc_cfg_attr *cfg)
+{
+	if (cfg->link) {
+		/*
+		 * write new offset = 1 to continue
+		 * processing the list
+		 */
+
+		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+
+		/* Reset link and prev_off */
+		dcc_ll_cfg_reset_link(cfg);
+	}
+
+	cfg->addr = DCC_RD_MOD_WR_DESCRIPTOR;
+	dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
+
+	dcc_sram_write_auto(drvdata, entry->mask, &cfg->sram_offset);
+
+	dcc_sram_write_auto(drvdata, entry->write_val, &cfg->sram_offset);
+
+	cfg->addr = 0;
+}
+
+static void dcc_emit_loop(struct dcc_drvdata *drvdata, struct dcc_config_entry *entry,
+			  struct dcc_cfg_attr *cfg,
+			  struct dcc_cfg_loop_attr *cfg_loop,
+			  u32 *total_len)
+{
+	int loop;
+
+	/* Check if we need to write link of prev entry */
+	if (cfg->link)
+		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+
+	if (cfg_loop->loop_start) {
+		loop = (cfg->sram_offset - cfg_loop->loop_off) / 4;
+		loop |= (cfg_loop->loop_cnt << drvdata->loop_shift) &
+				   GENMASK(DCC_ADDR_LIMIT, drvdata->loop_shift);
+		loop |= DCC_LOOP_DESCRIPTOR;
+		*total_len += (*total_len - cfg_loop->loop_len) * cfg_loop->loop_cnt;
+
+		dcc_sram_write_auto(drvdata, loop, &cfg->sram_offset);
+
+		cfg_loop->loop_start = false;
+		cfg_loop->loop_len = 0;
+		cfg_loop->loop_off = 0;
+	} else {
+		cfg_loop->loop_start = true;
+		cfg_loop->loop_cnt = entry->loop_cnt - 1;
+		cfg_loop->loop_len = *total_len;
+		cfg_loop->loop_off = cfg->sram_offset;
+	}
+
+	/* Reset link and prev_off */
+	dcc_ll_cfg_reset_link(cfg);
+}
+
+static void dcc_emit_write(struct dcc_drvdata *drvdata,
+			   struct dcc_config_entry *entry,
+			   struct dcc_cfg_attr *cfg)
+{
+	u32 off;
+
+	if (cfg->link) {
+		/*
+		 * write new offset = 1 to continue
+		 * processing the list
+		 */
+		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+
+		/* Reset link and prev_off */
+		cfg->addr = 0x00;
+		cfg->prev_off = 0;
+		cfg->prev_addr = cfg->addr;
+	}
+
+	off = entry->offset / 4;
+	/* write new offset-length pair to correct position */
+	cfg->link |= ((off & DCC_WRITE_OFF_MASK) | DCC_WRITE_MASK |
+		      FIELD_PREP(DCC_WRITE_LEN_MASK, entry->len));
+	cfg->link |= DCC_LINK_DESCRIPTOR;
+
+	/* Address type */
+	cfg->addr = (entry->base >> 4) & GENMASK(DCC_ADDR_LIMIT, 0);
+	if (entry->apb_bus)
+		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_APB_IND;
+	else
+		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_AHB_IND;
+	dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
+
+	dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+
+	dcc_sram_write_auto(drvdata, entry->write_val, &cfg->sram_offset);
+
+	cfg->addr = 0x00;
+	cfg->link = 0;
+}
+
+static int dcc_emit_read(struct dcc_drvdata *drvdata,
+			 struct dcc_config_entry *entry,
+			 struct dcc_cfg_attr *cfg,
+			 u32 *pos, u32 *total_len)
+{
+	u32 off;
+	u32 temp_off;
+
+	cfg->addr = (entry->base >> 4) & GENMASK(27, 0);
+
+	if (entry->apb_bus)
+		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_APB_IND;
+	else
+		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_AHB_IND;
+
+	off = entry->offset / 4;
+
+	*total_len += entry->len * 4;
+
+	if (!cfg->prev_addr || cfg->prev_addr != cfg->addr || cfg->prev_off > off) {
+		/* Check if we need to write prev link entry */
+		if (cfg->link)
+			dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+		dev_dbg(drvdata->dev, "DCC: sram address 0x%x\n", cfg->sram_offset);
+
+		/* Write address */
+		dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
+
+		/* Reset link and prev_off */
+		cfg->link = 0;
+		cfg->prev_off = 0;
+	}
+
+	if ((off - cfg->prev_off) > 0xff || entry->len > MAX_DCC_LEN) {
+		dev_err(drvdata->dev, "DCC: Programming error Base: 0x%x, offset 0x%x\n",
+			entry->base, entry->offset);
+		return -EINVAL;
+	}
+
+	if (cfg->link) {
+		/*
+		 * link already has one offset-length so new
+		 * offset-length needs to be placed at
+		 * bits [29:15]
+		 */
+		*pos = 15;
+
+		/* Clear bits [31:16] */
+		cfg->link &= GENMASK(14, 0);
+	} else {
+		/*
+		 * link is empty, so new offset-length needs
+		 * to be placed at bits [15:0]
+		 */
+		*pos = 0;
+		cfg->link = 1 << 15;
+	}
+
+	/* write new offset-length pair to correct position */
+	temp_off = (off - cfg->prev_off) & GENMASK(7, 0);
+	cfg->link |= temp_off | ((entry->len << 8) & GENMASK(14, 8)) << *pos;
+
+	cfg->link |= DCC_LINK_DESCRIPTOR;
+
+	if (*pos) {
+		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+		cfg->link = 0;
+	}
+
+	cfg->prev_off  = off + entry->len - 1;
+	cfg->prev_addr = cfg->addr;
+	return 0;
+}
+
+static int dcc_emit_config(struct dcc_drvdata *drvdata, unsigned int curr_list)
+{
+	int ret;
+	u32 total_len, pos;
+	struct dcc_config_entry *entry;
+	struct dcc_cfg_attr cfg;
+	struct dcc_cfg_loop_attr cfg_loop;
+
+	memset(&cfg, 0, sizeof(cfg));
+	memset(&cfg_loop, 0, sizeof(cfg_loop));
+	cfg.sram_offset = drvdata->ram_cfg * 4;
+	total_len = 0;
+
+	list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
+		switch (entry->desc_type) {
+		case DCC_READ_WRITE_TYPE:
+			dcc_emit_read_write(drvdata, entry, &cfg);
+			break;
+
+		case DCC_LOOP_TYPE:
+			dcc_emit_loop(drvdata, entry, &cfg, &cfg_loop, &total_len);
+			break;
+
+		case DCC_WRITE_TYPE:
+			dcc_emit_write(drvdata, entry, &cfg);
+			break;
+
+		case DCC_READ_TYPE:
+			ret = dcc_emit_read(drvdata, entry, &cfg, &pos, &total_len);
+			if (ret)
+				goto err;
+			break;
+		}
+	}
+
+	if (cfg.link)
+		dcc_sram_write_auto(drvdata, cfg.link, &cfg.sram_offset);
+
+	if (cfg_loop.loop_start) {
+		dev_err(drvdata->dev, "DCC: Programming error: Loop unterminated\n");
+		ret = -EINVAL;
+		goto err;
+	}
+
+	/* Handling special case of list ending with a rd_mod_wr */
+	if (cfg.addr == DCC_RD_MOD_WR_DESCRIPTOR) {
+		cfg.addr = (DCC_RD_MOD_WR_ADDR) & GENMASK(27, 0);
+		cfg.addr |= DCC_ADDR_DESCRIPTOR;
+		dcc_sram_write_auto(drvdata, cfg.addr, &cfg.sram_offset);
+	}
+
+	/* Setting zero to indicate end of the list */
+	cfg.link = DCC_LINK_DESCRIPTOR;
+	dcc_sram_write_auto(drvdata, cfg.link, &cfg.sram_offset);
+
+	/* Check if sram offset exceeds the ram size */
+	if (cfg.sram_offset > drvdata->ram_size)
+		goto overstep;
+
+	/* Update ram_cfg and check if the data will overstep */
+	drvdata->ram_cfg = (cfg.sram_offset + total_len) / 4;
+
+	if (cfg.sram_offset + total_len > drvdata->ram_size) {
+		cfg.sram_offset += total_len;
+		goto overstep;
+	}
+
+	drvdata->ram_start = cfg.sram_offset / 4;
+	return 0;
+overstep:
+	ret = -EINVAL;
+	memset_io(drvdata->ram_base, 0, drvdata->ram_size);
+
+err:
+	return ret;
+}
+
+static bool dcc_valid_list(struct dcc_drvdata *drvdata, unsigned int curr_list)
+{
+	u32 lock_reg;
+
+	if (list_empty(&drvdata->cfg_head[curr_list]))
+		return false;
+
+	if (test_bit(curr_list, drvdata->enable_bitmap)) {
+		dev_err(drvdata->dev, "List %d is already enabled\n", curr_list);
+		return false;
+	}
+
+	lock_reg = dcc_list_readl(drvdata, curr_list, DCC_LL_LOCK);
+	if (lock_reg & DCC_LOCK_MASK) {
+		dev_err(drvdata->dev, "List %d is already locked\n", curr_list);
+		return false;
+	}
+
+	return true;
+}
+
+static bool is_dcc_enabled(struct dcc_drvdata *drvdata)
+{
+	int list;
+
+	for (list = 0; list < drvdata->nr_link_list; list++)
+		if (test_bit(list, drvdata->enable_bitmap))
+			return true;
+
+	return false;
+}
+
+static int dcc_enable(struct dcc_drvdata *drvdata, unsigned int curr_list)
+{
+	int ret;
+	u32 ram_cfg_base;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (!dcc_valid_list(drvdata, curr_list)) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	/* Fill dcc sram with the poison value.
+	 * This helps in understanding bus
+	 * hang from registers returning a zero
+	 */
+	if (!is_dcc_enabled(drvdata))
+		memset_io(drvdata->ram_base, 0xde, drvdata->ram_size);
+
+	/* 1. Take ownership of the list */
+	dcc_list_writel(drvdata, DCC_LOCK_MASK, curr_list, DCC_LL_LOCK);
+
+	/* 2. Program linked-list in the SRAM */
+	ram_cfg_base = drvdata->ram_cfg;
+	ret = dcc_emit_config(drvdata, curr_list);
+	if (ret) {
+		dcc_list_writel(drvdata, 0, curr_list, DCC_LL_LOCK);
+		goto out_unlock;
+	}
+
+	/* 3. Program DCC_RAM_CFG reg */
+	dcc_list_writel(drvdata, ram_cfg_base +
+			drvdata->ram_offset / 4, curr_list, DCC_LL_BASE);
+	dcc_list_writel(drvdata, drvdata->ram_start +
+			drvdata->ram_offset / 4, curr_list, DCC_FD_BASE);
+	dcc_list_writel(drvdata, 0xFFF, curr_list, DCC_LL_TIMEOUT);
+
+	/* 4. Clears interrupt status register */
+	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_INT_ENABLE);
+	dcc_list_writel(drvdata, (BIT(0) | BIT(1) | BIT(2)),
+			curr_list, DCC_LL_INT_STATUS);
+
+	set_bit(curr_list, drvdata->enable_bitmap);
+
+	/* 5. Configure trigger */
+	dcc_list_writel(drvdata, DCC_TRIGGER_MASK,
+			curr_list, DCC_LL_CFG);
+
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+	return ret;
+}
+
+static void dcc_disable(struct dcc_drvdata *drvdata, int curr_list)
+{
+	mutex_lock(&drvdata->mutex);
+
+	if (!test_bit(curr_list, drvdata->enable_bitmap))
+		goto out_unlock;
+	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_CFG);
+	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_BASE);
+	dcc_list_writel(drvdata, 0, curr_list, DCC_FD_BASE);
+	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_LOCK);
+	clear_bit(curr_list, drvdata->enable_bitmap);
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+}
+
+static u32 dcc_filp_curr_list(const struct file *filp)
+{
+	struct dentry *dentry = file_dentry(filp);
+	int curr_list, ret;
+
+	ret = kstrtoint(dentry->d_parent->d_name.name, 0, &curr_list);
+	if (ret)
+		return ret;
+
+	return curr_list;
+}
+
+static ssize_t enable_read(struct file *filp, char __user *userbuf,
+			   size_t count, loff_t *ppos)
+{
+	char *buf;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (is_dcc_enabled(drvdata))
+		buf = "Y\n";
+	else
+		buf = "N\n";
+
+	mutex_unlock(&drvdata->mutex);
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf));
+}
+
+static ssize_t enable_write(struct file *filp, const char __user *userbuf,
+			    size_t count, loff_t *ppos)
+{
+	int ret = 0, curr_list;
+	bool val;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	curr_list = dcc_filp_curr_list(filp);
+	if (curr_list < 0)
+		return curr_list;
+
+	ret = kstrtobool_from_user(userbuf, count, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val) {
+		ret = dcc_enable(drvdata, curr_list);
+		if (ret)
+			return ret;
+	} else {
+		dcc_disable(drvdata, curr_list);
+	}
+
+	return count;
+}
+
+static const struct file_operations enable_fops = {
+	.read = enable_read,
+	.write = enable_write,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
+static ssize_t trigger_write(struct file *filp,
+			     const char __user *user_buf, size_t count,
+			     loff_t *ppos)
+{
+	int ret;
+	unsigned int val;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	ret = kstrtouint_from_user(user_buf, count, 0, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val != 1)
+		return -EINVAL;
+
+	ret = dcc_sw_trigger(drvdata);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static const struct file_operations trigger_fops = {
+	.write = trigger_write,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
+static int dcc_config_add(struct dcc_drvdata *drvdata, unsigned int addr,
+			  unsigned int len, bool apb_bus, int curr_list)
+{
+	int ret = 0;
+	struct dcc_config_entry *entry, *pentry;
+	unsigned int base, offset;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (!len || len > drvdata->ram_size / DCC_WORD_SIZE) {
+		dev_err(drvdata->dev, "DCC: Invalid length\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	base = addr & DCC_ADDR_RANGE_MASK;
+
+	if (!list_empty(&drvdata->cfg_head[curr_list])) {
+		pentry = list_last_entry(&drvdata->cfg_head[curr_list],
+					 struct dcc_config_entry, list);
+
+		if (pentry->desc_type == DCC_READ_TYPE &&
+		    addr >= (pentry->base + pentry->offset) &&
+		    addr <= (pentry->base + pentry->offset + MAX_DCC_OFFSET)) {
+			/* Re-use base address from last entry */
+			base = pentry->base;
+
+			if ((pentry->len * 4 + pentry->base + pentry->offset)
+					== addr) {
+				len += pentry->len;
+
+				if (len > MAX_DCC_LEN)
+					pentry->len = MAX_DCC_LEN;
+				else
+					pentry->len = len;
+
+				addr = pentry->base + pentry->offset +
+					pentry->len * 4;
+				len -= pentry->len;
+			}
+		}
+	}
+
+	offset = addr - base;
+
+	while (len) {
+		entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+		if (!entry) {
+			ret = -ENOMEM;
+			goto out_unlock;
+		}
+
+		entry->base = base;
+		entry->offset = offset;
+		entry->len = min_t(u32, len, MAX_DCC_LEN);
+		entry->desc_type = DCC_READ_TYPE;
+		entry->apb_bus = apb_bus;
+		INIT_LIST_HEAD(&entry->list);
+		list_add_tail(&entry->list,
+			      &drvdata->cfg_head[curr_list]);
+
+		len -= entry->len;
+		offset += MAX_DCC_LEN * 4;
+	}
+
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+	return ret;
+}
+
+static ssize_t dcc_config_add_read(struct dcc_drvdata *drvdata, char *buf, int curr_list)
+{
+	bool bus;
+	int len, nval;
+	unsigned int base;
+	char apb_bus[4];
+
+	nval = sscanf(buf, "%x %i %3s", &base, &len, apb_bus);
+	if (nval <= 0 || nval > 3)
+		return -EINVAL;
+
+	if (nval == 1) {
+		len = 1;
+		bus = false;
+	} else if (nval == 2) {
+		bus = false;
+	} else if (!strcmp("apb", apb_bus)) {
+		bus = true;
+	} else if (!strcmp("ahb", apb_bus)) {
+		bus = false;
+	} else {
+		return -EINVAL;
+	}
+
+	return dcc_config_add(drvdata, base, len, bus, curr_list);
+}
+
+static void dcc_config_reset(struct dcc_drvdata *drvdata)
+{
+	struct dcc_config_entry *entry, *temp;
+	int curr_list;
+
+	mutex_lock(&drvdata->mutex);
+
+	for (curr_list = 0; curr_list < drvdata->nr_link_list; curr_list++) {
+		list_for_each_entry_safe(entry, temp,
+					 &drvdata->cfg_head[curr_list], list) {
+			list_del(&entry->list);
+			kfree(entry);
+		}
+	}
+	drvdata->ram_start = 0;
+	drvdata->ram_cfg = 0;
+	mutex_unlock(&drvdata->mutex);
+}
+
+static ssize_t config_reset_write(struct file *filp,
+				  const char __user *user_buf, size_t count,
+				  loff_t *ppos)
+{
+	unsigned int val, ret;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	ret = kstrtouint_from_user(user_buf, count, 0, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val)
+		dcc_config_reset(drvdata);
+
+	return count;
+}
+
+static const struct file_operations config_reset_fops = {
+	.write = config_reset_write,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
+static ssize_t ready_read(struct file *filp, char __user *userbuf,
+			  size_t count, loff_t *ppos)
+{
+	int ret = 0;
+	char *buf;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (!is_dcc_enabled(drvdata)) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (!FIELD_GET(BIT(1), readl(drvdata->base + DCC_STATUS(drvdata->mem_map_ver))))
+		buf = "Y\n";
+	else
+		buf = "N\n";
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+
+	if (ret < 0)
+		return -EINVAL;
+	else
+		return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf) + 1);
+}
+
+static const struct file_operations ready_fops = {
+	.read = ready_read,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
+static int dcc_add_loop(struct dcc_drvdata *drvdata, unsigned long loop_cnt, int curr_list)
+{
+	struct dcc_config_entry *entry;
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->loop_cnt = min_t(u32, loop_cnt, MAX_LOOP_CNT);
+	entry->desc_type = DCC_LOOP_TYPE;
+	INIT_LIST_HEAD(&entry->list);
+	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
+
+	return 0;
+}
+
+static ssize_t dcc_config_add_loop(struct dcc_drvdata *drvdata, char *buf, int curr_list)
+{
+	int ret, i = 0;
+	char *token, *input;
+	char delim[2] = " ";
+	unsigned int val[MAX_LOOP_ADDR];
+
+	input = buf;
+
+	while ((token = strsep(&input, delim)) && i < MAX_LOOP_ADDR) {
+		ret = kstrtoint(token, 0, &val[i++]);
+		if (ret)
+			return ret;
+	}
+
+	if (token) {
+		dev_err(drvdata->dev, "Max limit %u of loop address exceeded",
+			MAX_LOOP_ADDR);
+		return -EINVAL;
+	}
+
+	if (val[1] < 1 || val[1] > 8)
+		return -EINVAL;
+
+	ret = dcc_add_loop(drvdata, val[0], curr_list);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < val[1]; i++)
+		dcc_config_add(drvdata, val[i + 2], 1, false, curr_list);
+
+	return dcc_add_loop(drvdata, 1, curr_list);
+}
+
+static int dcc_rd_mod_wr_add(struct dcc_drvdata *drvdata, unsigned int mask,
+			     unsigned int val, int curr_list)
+{
+	int ret = 0;
+	struct dcc_config_entry *entry;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (list_empty(&drvdata->cfg_head[curr_list])) {
+		dev_err(drvdata->dev, "DCC: No read address programmed\n");
+		ret = -EPERM;
+		goto out_unlock;
+	}
+
+	entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
+	if (!entry) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	entry->desc_type = DCC_READ_WRITE_TYPE;
+	entry->mask = mask;
+	entry->write_val = val;
+	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+	return ret;
+}
+
+static ssize_t dcc_config_add_read_write(struct dcc_drvdata *drvdata, char *buf, int curr_list)
+{
+	int ret;
+	int nval;
+	unsigned int addr, mask, val;
+
+	nval = sscanf(buf, "%x %x %x", &addr, &mask, &val);
+
+	if (nval <= 1 || nval > 3)
+		return -EINVAL;
+
+	ret = dcc_config_add(drvdata, addr, 1, false, curr_list);
+	if (ret)
+		return ret;
+
+	return dcc_rd_mod_wr_add(drvdata, mask, val, curr_list);
+}
+
+static int dcc_add_write(struct dcc_drvdata *drvdata, unsigned int addr,
+			 unsigned int write_val, int apb_bus, int curr_list)
+{
+	struct dcc_config_entry *entry;
+
+	entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->desc_type = DCC_WRITE_TYPE;
+	entry->base = addr & GENMASK(31, 4);
+	entry->offset = addr - entry->base;
+	entry->write_val = write_val;
+	entry->len = 1;
+	entry->apb_bus = apb_bus;
+	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
+
+	return 0;
+}
+
+static ssize_t dcc_config_add_write(struct dcc_drvdata *drvdata, char *buf, int curr_list)
+{
+	bool bus;
+	int nval;
+	unsigned int addr, write_val;
+	char apb_bus[4];
+
+	nval = sscanf(buf, "%x %x %3s", &addr, &write_val, apb_bus);
+
+	if (nval <= 1 || nval > 3)
+		return -EINVAL;
+
+	if (nval == 2)
+		bus = true;
+
+	if (nval == 3) {
+		if (!strcmp("apb", apb_bus))
+			bus = true;
+		else if (!strcmp("ahb", apb_bus))
+			bus = false;
+		else
+			return -EINVAL;
+	}
+
+	return dcc_add_write(drvdata, addr, write_val, bus, curr_list);
+}
+
+static int config_show(struct seq_file *m, void *data)
+{
+	struct dcc_drvdata *drvdata = m->private;
+	struct dcc_config_entry *entry;
+	int index = 0, curr_list;
+
+	curr_list = dcc_filp_curr_list(m->file);
+	if (curr_list < 0)
+		return curr_list;
+
+	mutex_lock(&drvdata->mutex);
+
+	list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
+		index++;
+		switch (entry->desc_type) {
+		case DCC_READ_WRITE_TYPE:
+			seq_printf(m, "RW mask: 0x%x, val: 0x%x\n index: 0x%x\n",
+				   entry->mask, entry->write_val, index);
+			break;
+		case DCC_LOOP_TYPE:
+			seq_printf(m, "L index: 0x%x Loop: %d\n", index, entry->loop_cnt);
+			break;
+		case DCC_WRITE_TYPE:
+			seq_printf(m, "W Base:0x%x, Offset: 0x%x, val: 0x%x, APB: %d\n, Index: 0x%x\n",
+				   entry->base, entry->offset, entry->write_val, entry->apb_bus,
+				   index);
+			break;
+		case DCC_READ_TYPE:
+			seq_printf(m, "R Base:0x%x, Offset: 0x%x, len: 0x%x, APB: %d\n, Index: 0x%x\n",
+				   entry->base, entry->offset, entry->len, entry->apb_bus, index);
+		}
+	}
+	mutex_unlock(&drvdata->mutex);
+	return 0;
+}
+
+static int config_open(struct inode *inode, struct file *file)
+{
+	struct dcc_drvdata *drvdata = inode->i_private;
+
+	return single_open(file, config_show, drvdata);
+}
+
+static ssize_t config_write(struct file *filp,
+			    const char __user *user_buf, size_t count,
+			    loff_t *ppos)
+{
+	int ret, curr_list;
+	char *token, buf[50];
+	char *bufp = buf;
+	char *delim = " ";
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	if (count > sizeof(buf) || count == 0)
+		return -EINVAL;
+
+	ret = copy_from_user(buf, user_buf, count);
+	if (ret)
+		return -EFAULT;
+
+	curr_list = dcc_filp_curr_list(filp);
+	if (curr_list < 0)
+		return curr_list;
+
+	if (buf[count - 1] == '\n')
+		buf[count - 1] = '\0';
+	else
+		return -EINVAL;
+
+	token = strsep(&bufp, delim);
+
+	if (!strcmp("R", token)) {
+		ret = dcc_config_add_read(drvdata, bufp, curr_list);
+	} else if (!strcmp("W", token)) {
+		ret = dcc_config_add_write(drvdata, bufp, curr_list);
+	} else if (!strcmp("RW", token)) {
+		ret = dcc_config_add_read_write(drvdata, bufp, curr_list);
+	} else if (!strcmp("L", token)) {
+		ret = dcc_config_add_loop(drvdata, bufp, curr_list);
+	} else {
+		dev_err(drvdata->dev, "%s is not a correct input\n", token);
+		return -EINVAL;
+	}
+
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static const struct file_operations config_fops = {
+	.open = config_open,
+	.read = seq_read,
+	.write = config_write,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
+static void dcc_delete_debug_dir(struct dcc_drvdata *drvdata)
+{
+	 debugfs_remove_recursive(drvdata->dbg_dir);
+};
+
+static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
+{
+	int i;
+	char list_num[10];
+	struct dentry *list;
+	struct device *dev = drvdata->dev;
+
+	drvdata->dbg_dir = debugfs_create_dir(dev_name(dev), NULL);
+	if (IS_ERR(drvdata->dbg_dir)) {
+		pr_err("can't create debugfs dir\n");
+		return;
+	}
+
+	for (i = 0; i <= drvdata->nr_link_list; i++) {
+		sprintf(list_num, "%d", i);
+		list = debugfs_create_dir(list_num, drvdata->dbg_dir);
+		debugfs_create_file("enable", 0600, list, drvdata, &enable_fops);
+		debugfs_create_file("config", 0600, list, drvdata, &config_fops);
+	}
+
+	debugfs_create_file("trigger", 0200, drvdata->dbg_dir, drvdata, &trigger_fops);
+	debugfs_create_file("ready", 0400, drvdata->dbg_dir, drvdata, &ready_fops);
+	debugfs_create_file("config_reset", 0200, drvdata->dbg_dir,
+			    drvdata, &config_reset_fops);
+}
+
+static ssize_t dcc_sram_read(struct file *file, char __user *data,
+			     size_t len, loff_t *ppos)
+{
+	unsigned char *buf;
+	struct dcc_drvdata *drvdata;
+
+	drvdata = container_of(file->private_data, struct dcc_drvdata,
+			       sram_dev);
+
+	/* EOF check */
+	if (*ppos >= drvdata->ram_size)
+		return 0;
+
+	if ((*ppos + len) > drvdata->ram_size)
+		len = (drvdata->ram_size - *ppos);
+
+	buf = kzalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	memcpy_fromio(buf, drvdata->ram_base + *ppos, len);
+
+	if (copy_to_user(data, buf, len)) {
+		kfree(buf);
+		return -EFAULT;
+	}
+
+	*ppos += len;
+
+	kfree(buf);
+
+	return len;
+}
+
+static const struct file_operations dcc_sram_fops = {
+	.owner		= THIS_MODULE,
+	.read		= dcc_sram_read,
+	.llseek		= no_llseek,
+};
+
+static int dcc_sram_dev_init(struct dcc_drvdata *drvdata)
+{
+	drvdata->sram_dev.minor = MISC_DYNAMIC_MINOR;
+	drvdata->sram_dev.name = DCC_SRAM_NODE;
+	drvdata->sram_dev.fops = &dcc_sram_fops;
+
+	return misc_register(&drvdata->sram_dev);
+}
+
+static void dcc_sram_dev_exit(struct dcc_drvdata *drvdata)
+{
+	misc_deregister(&drvdata->sram_dev);
+}
+
+static int dcc_probe(struct platform_device *pdev)
+{
+	u32 val;
+	int ret = 0, i;
+	struct device *dev = &pdev->dev;
+	struct dcc_drvdata *drvdata;
+	struct resource *res;
+
+	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+
+	drvdata->dev = &pdev->dev;
+	platform_set_drvdata(pdev, drvdata);
+
+	drvdata->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(drvdata->base))
+		return PTR_ERR(drvdata->base);
+
+	drvdata->ram_base = devm_platform_get_and_ioremap_resource(pdev, 1, &res);
+	if (IS_ERR(drvdata->ram_base))
+		return PTR_ERR(drvdata->ram_base);
+
+	drvdata->ram_size = resource_size(res);
+
+	drvdata->ram_offset = (size_t)of_device_get_match_data(&pdev->dev);
+
+	val = readl(drvdata->base + DCC_HW_INFO);
+
+	if (FIELD_GET(DCC_VER_INFO_MASK, val)) {
+		drvdata->mem_map_ver = 3;
+		drvdata->nr_link_list = readl(drvdata->base + DCC_LL_NUM_INFO);
+		if (!drvdata->nr_link_list)
+			return	-EINVAL;
+	} else if ((val & DCC_VER_MASK2) == DCC_VER_MASK2) {
+		drvdata->mem_map_ver = 2;
+		drvdata->nr_link_list = readl(drvdata->base + DCC_LL_NUM_INFO);
+		if (!drvdata->nr_link_list)
+			return	-EINVAL;
+	} else {
+		drvdata->mem_map_ver = 1;
+		drvdata->nr_link_list = DCC_MAX_LINK_LIST;
+	}
+
+	/* Either set the fixed loop offset or calculate
+	 * it from the total number of words in dcc_sram.
+	 * Max consecutive addresses dcc can loop is
+	 * equivalent to the words in dcc_sram.
+	 */
+	if (val & DCC_LOOP_OFFSET_MASK)
+		drvdata->loop_shift = DCC_FIX_LOOP_OFFSET;
+	else
+		drvdata->loop_shift = get_bitmask_order((drvdata->ram_offset +
+					drvdata->ram_size) / DCC_SRAM_WORD_LENGTH - 1);
+
+	mutex_init(&drvdata->mutex);
+
+	drvdata->enable_bitmap = devm_kcalloc(dev, BITS_TO_LONGS(drvdata->nr_link_list),
+					      sizeof(*drvdata->enable_bitmap), GFP_KERNEL);
+	if (!drvdata->enable_bitmap)
+		return -ENOMEM;
+
+	drvdata->cfg_head = devm_kcalloc(dev, drvdata->nr_link_list,
+					 sizeof(*drvdata->cfg_head), GFP_KERNEL);
+	if (!drvdata->cfg_head)
+		return -ENOMEM;
+
+	for (i = 0; i < drvdata->nr_link_list; i++)
+		INIT_LIST_HEAD(&drvdata->cfg_head[i]);
+
+	ret = dcc_sram_dev_init(drvdata);
+	if (ret) {
+		dev_err(drvdata->dev, "DCC: sram node not registered.\n");
+		return ret;
+	}
+
+	dcc_create_debug_dir(drvdata);
+
+	return 0;
+}
+
+static int dcc_remove(struct platform_device *pdev)
+{
+	struct dcc_drvdata *drvdata = platform_get_drvdata(pdev);
+
+	dcc_delete_debug_dir(drvdata);
+	dcc_sram_dev_exit(drvdata);
+	dcc_config_reset(drvdata);
+
+	return 0;
+}
+
+static const struct of_device_id dcc_match_table[] = {
+	{ .compatible = "qcom,sc7180-dcc", .data = (void *)0x6000 },
+	{ .compatible = "qcom,sc7280-dcc", .data = (void *)0x12000 },
+	{ .compatible = "qcom,sdm845-dcc", .data = (void *)0x6000 },
+	{ .compatible = "qcom,sm8150-dcc", .data = (void *)0x5000 },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dcc_match_table);
+
+static struct platform_driver dcc_driver = {
+	.probe = dcc_probe,
+	.remove	= dcc_remove,
+	.driver	= {
+		.name = "qcom-dcc",
+		.of_match_table	= dcc_match_table,
+	},
+};
+
+module_platform_driver(dcc_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Qualcomm Technologies Inc. DCC driver");
+
-- 
2.7.4

Re: [PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

[Greg Kroah-Hartman]

On Fri, Apr 14, 2023 at 07:29:12PM +0530, Souradeep Chowdhury wrote:
> The DCC is a DMA Engine designed to capture and store data
> during system crash or software triggers. The DCC operates
> based on user inputs via the debugfs interface. The user gives
> addresses as inputs and these addresses are stored in the
> dcc sram. In case of a system crash or a manual software
> trigger by the user through the debugfs interface,
> the dcc captures and stores the values at these addresses.
> This patch contains the driver which has all the methods
> pertaining to the debugfs interface, auxiliary functions to
> support all the four fundamental operations of dcc namely
> read, write, read/modify/write and loop. The probe method
> here instantiates all the resources necessary for dcc to
> operate mainly the dedicated dcc sram where it stores the
> values. The DCC driver can be used for debugging purposes
> without going for a reboot since it can perform software
> triggers as well based on user inputs.

You have 72 columns, why not use them all please?

> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
> + * Copyright (c) 2022, Qualcomm Innovation Center, Inc. All rights reserved.

It is now 2023 :)




> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/debugfs.h>
> +#include <linux/delay.h>
> +#include <linux/fs.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/miscdevice.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +#define STATUS_READY_TIMEOUT		5000  /* microseconds */
> +
> +#define DCC_SRAM_NODE "dcc_sram"

You only use this once, why is a #define needed?

> +static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
> +{
> +	int i;
> +	char list_num[10];
> +	struct dentry *list;
> +	struct device *dev = drvdata->dev;
> +
> +	drvdata->dbg_dir = debugfs_create_dir(dev_name(dev), NULL);

You are creating a directory at the root of debugfs with just your
device name?  While that will work, that feels very odd.  Please use a
subdirectory.

> +	if (IS_ERR(drvdata->dbg_dir)) {
> +		pr_err("can't create debugfs dir\n");

There is no need to ever check the return value of a debugfs call.

Nor do you really ever even need to save off the dentry here, just look
it up when you need to remove it.

> +		return;
> +	}
> +
> +	for (i = 0; i <= drvdata->nr_link_list; i++) {
> +		sprintf(list_num, "%d", i);
> +		list = debugfs_create_dir(list_num, drvdata->dbg_dir);
> +		debugfs_create_file("enable", 0600, list, drvdata, &enable_fops);
> +		debugfs_create_file("config", 0600, list, drvdata, &config_fops);
> +	}
> +
> +	debugfs_create_file("trigger", 0200, drvdata->dbg_dir, drvdata, &trigger_fops);
> +	debugfs_create_file("ready", 0400, drvdata->dbg_dir, drvdata, &ready_fops);
> +	debugfs_create_file("config_reset", 0200, drvdata->dbg_dir,
> +			    drvdata, &config_reset_fops);

This really looks like you are using debugfs to control the device, not
just for debugging information.  How are you going to be able to use the
device in a system that has debugfs disabled?

thanks,

greg k-h

Re: [PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

[Souradeep Chowdhury]

On 4/15/2023 11:09 AM, Greg Kroah-Hartman wrote:
> On Fri, Apr 14, 2023 at 07:29:12PM +0530, Souradeep Chowdhury wrote:
>> The DCC is a DMA Engine designed to capture and store data
>> during system crash or software triggers. The DCC operates
>> based on user inputs via the debugfs interface. The user gives
>> addresses as inputs and these addresses are stored in the
>> dcc sram. In case of a system crash or a manual software
>> trigger by the user through the debugfs interface,
>> the dcc captures and stores the values at these addresses.
>> This patch contains the driver which has all the methods
>> pertaining to the debugfs interface, auxiliary functions to
>> support all the four fundamental operations of dcc namely
>> read, write, read/modify/write and loop. The probe method
>> here instantiates all the resources necessary for dcc to
>> operate mainly the dedicated dcc sram where it stores the
>> values. The DCC driver can be used for debugging purposes
>> without going for a reboot since it can perform software
>> triggers as well based on user inputs.
> 
> You have 72 columns, why not use them all please?
> 
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
>> + * Copyright (c) 2022, Qualcomm Innovation Center, Inc. All rights reserved.
> 
> It is now 2023 :)

Ack

> 
> 
> 
> 
>> + */
>> +
>> +#include <linux/bitfield.h>
>> +#include <linux/bitops.h>
>> +#include <linux/debugfs.h>
>> +#include <linux/delay.h>
>> +#include <linux/fs.h>
>> +#include <linux/io.h>
>> +#include <linux/iopoll.h>
>> +#include <linux/miscdevice.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_device.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/slab.h>
>> +#include <linux/uaccess.h>
>> +
>> +#define STATUS_READY_TIMEOUT		5000  /* microseconds */
>> +
>> +#define DCC_SRAM_NODE "dcc_sram"
> 
> You only use this once, why is a #define needed?

This is as per the comment on version 1 of the patch series on DCC

https://lore.kernel.org/linux-arm-kernel/YElUCaBUOx7hEuIh@builder.lan/

"kzalloc + strlcpy can be replaced by kstrdup(), but that said...all 
this does seems to be to copy a const string to the heap and lugging it
around. Use a define instead."


> 
>> +static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
>> +{
>> +	int i;
>> +	char list_num[10];
>> +	struct dentry *list;
>> +	struct device *dev = drvdata->dev;
>> +
>> +	drvdata->dbg_dir = debugfs_create_dir(dev_name(dev), NULL);
> 
> You are creating a directory at the root of debugfs with just your
> device name?  While that will work, that feels very odd.  Please use a
> subdirectory.

This is as per the comment on v17 of the patch series on DCC

https://lore.kernel.org/linux-arm-kernel/6693993c-bd81-c974-a903-52a62bfec606@ieee.org/

"You never remove this dcc_dbg directory.  Why not?

And since you don't, dcc_dbg could just be a local
variable here rather than being a global.  But it
seems to me this is the root directory you want to
remove when you're done."


> 
>> +	if (IS_ERR(drvdata->dbg_dir)) {
>> +		pr_err("can't create debugfs dir\n");
> 
> There is no need to ever check the return value of a debugfs call.
> 
> Nor do you really ever even need to save off the dentry here, just look
> it up when you need to remove it.

Ack

> 
>> +		return;
>> +	}
>> +
>> +	for (i = 0; i <= drvdata->nr_link_list; i++) {
>> +		sprintf(list_num, "%d", i);
>> +		list = debugfs_create_dir(list_num, drvdata->dbg_dir);
>> +		debugfs_create_file("enable", 0600, list, drvdata, &enable_fops);
>> +		debugfs_create_file("config", 0600, list, drvdata, &config_fops);
>> +	}
>> +
>> +	debugfs_create_file("trigger", 0200, drvdata->dbg_dir, drvdata, &trigger_fops);
>> +	debugfs_create_file("ready", 0400, drvdata->dbg_dir, drvdata, &ready_fops);
>> +	debugfs_create_file("config_reset", 0200, drvdata->dbg_dir,
>> +			    drvdata, &config_reset_fops);
> 
> This really looks like you are using debugfs to control the device, not
> just for debugging information.  How are you going to be able to use the
> device in a system that has debugfs disabled?

As per upstream discussions it was decided that debugfs will be a 
suitable interface for DCC. More on this in the following link:-

https://lore.kernel.org/linux-arm-kernel/20221228172825.r32vpphbdulaldvv@builder.lan/

> 
> thanks,
> 
> greg k-h

Re: [PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

[Greg Kroah-Hartman]

On Mon, Apr 17, 2023 at 11:31:46AM +0530, Souradeep Chowdhury wrote:
> 
> 
> On 4/15/2023 11:09 AM, Greg Kroah-Hartman wrote:
> > On Fri, Apr 14, 2023 at 07:29:12PM +0530, Souradeep Chowdhury wrote:
> > > The DCC is a DMA Engine designed to capture and store data
> > > during system crash or software triggers. The DCC operates
> > > based on user inputs via the debugfs interface. The user gives
> > > addresses as inputs and these addresses are stored in the
> > > dcc sram. In case of a system crash or a manual software
> > > trigger by the user through the debugfs interface,
> > > the dcc captures and stores the values at these addresses.
> > > This patch contains the driver which has all the methods
> > > pertaining to the debugfs interface, auxiliary functions to
> > > support all the four fundamental operations of dcc namely
> > > read, write, read/modify/write and loop. The probe method
> > > here instantiates all the resources necessary for dcc to
> > > operate mainly the dedicated dcc sram where it stores the
> > > values. The DCC driver can be used for debugging purposes
> > > without going for a reboot since it can perform software
> > > triggers as well based on user inputs.
> > 
> > You have 72 columns, why not use them all please?
> > 
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
> > > + * Copyright (c) 2022, Qualcomm Innovation Center, Inc. All rights reserved.
> > 
> > It is now 2023 :)
> 
> Ack
> 
> > 
> > 
> > 
> > 
> > > + */
> > > +
> > > +#include <linux/bitfield.h>
> > > +#include <linux/bitops.h>
> > > +#include <linux/debugfs.h>
> > > +#include <linux/delay.h>
> > > +#include <linux/fs.h>
> > > +#include <linux/io.h>
> > > +#include <linux/iopoll.h>
> > > +#include <linux/miscdevice.h>
> > > +#include <linux/module.h>
> > > +#include <linux/of.h>
> > > +#include <linux/of_device.h>
> > > +#include <linux/platform_device.h>
> > > +#include <linux/slab.h>
> > > +#include <linux/uaccess.h>
> > > +
> > > +#define STATUS_READY_TIMEOUT		5000  /* microseconds */
> > > +
> > > +#define DCC_SRAM_NODE "dcc_sram"
> > 
> > You only use this once, why is a #define needed?
> 
> This is as per the comment on version 1 of the patch series on DCC
> 
> https://lore.kernel.org/linux-arm-kernel/YElUCaBUOx7hEuIh@builder.lan/
> 
> "kzalloc + strlcpy can be replaced by kstrdup(), but that said...all this
> does seems to be to copy a const string to the heap and lugging it
> around. Use a define instead."

But as you are not doing any of that here, just using the string in the
one place it is needed is the same thing :)

> > > +static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
> > > +{
> > > +	int i;
> > > +	char list_num[10];
> > > +	struct dentry *list;
> > > +	struct device *dev = drvdata->dev;
> > > +
> > > +	drvdata->dbg_dir = debugfs_create_dir(dev_name(dev), NULL);
> > 
> > You are creating a directory at the root of debugfs with just your
> > device name?  While that will work, that feels very odd.  Please use a
> > subdirectory.
> 
> This is as per the comment on v17 of the patch series on DCC
> 
> https://lore.kernel.org/linux-arm-kernel/6693993c-bd81-c974-a903-52a62bfec606@ieee.org/
> 
> "You never remove this dcc_dbg directory.  Why not?
> 
> And since you don't, dcc_dbg could just be a local
> variable here rather than being a global.  But it
> seems to me this is the root directory you want to
> remove when you're done."

But that's not the issue.  The issue is that you are putting into
/sys/kernel/debug/ a flat namespace of all of your devices.  Is that
really what you want?  If so, why do you think this will never conflict
with any other device in the system?

> > > +	if (IS_ERR(drvdata->dbg_dir)) {
> > > +		pr_err("can't create debugfs dir\n");
> > 
> > There is no need to ever check the return value of a debugfs call.
> > 
> > Nor do you really ever even need to save off the dentry here, just look
> > it up when you need to remove it.
> 
> Ack
> 
> > 
> > > +		return;
> > > +	}
> > > +
> > > +	for (i = 0; i <= drvdata->nr_link_list; i++) {
> > > +		sprintf(list_num, "%d", i);
> > > +		list = debugfs_create_dir(list_num, drvdata->dbg_dir);
> > > +		debugfs_create_file("enable", 0600, list, drvdata, &enable_fops);
> > > +		debugfs_create_file("config", 0600, list, drvdata, &config_fops);
> > > +	}
> > > +
> > > +	debugfs_create_file("trigger", 0200, drvdata->dbg_dir, drvdata, &trigger_fops);
> > > +	debugfs_create_file("ready", 0400, drvdata->dbg_dir, drvdata, &ready_fops);
> > > +	debugfs_create_file("config_reset", 0200, drvdata->dbg_dir,
> > > +			    drvdata, &config_reset_fops);
> > 
> > This really looks like you are using debugfs to control the device, not
> > just for debugging information.  How are you going to be able to use the
> > device in a system that has debugfs disabled?
> 
> As per upstream discussions it was decided that debugfs will be a suitable
> interface for DCC. More on this in the following link:-
> 
> https://lore.kernel.org/linux-arm-kernel/20221228172825.r32vpphbdulaldvv@builder.lan/

debugfs is not a suitable interface for anything that is "real" as
that's not what it is there for.  Most systems disable debugfs entirely
(i.e. Android), or prevent any normal user from accessing it, so this
api you are creating will not be able to be used by anyone.

debugfs is for debugging, not for anything that the system functionality
relies on to work properly.

Also, that was a v21 of the patch series, why did the numbering start
over here at v1?

thanks,

greg k-h

Re: [PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

[Souradeep Chowdhury]

On 4/17/2023 11:47 AM, Greg Kroah-Hartman wrote:
> On Mon, Apr 17, 2023 at 11:31:46AM +0530, Souradeep Chowdhury wrote:
>>
>>
>> On 4/15/2023 11:09 AM, Greg Kroah-Hartman wrote:
>>> On Fri, Apr 14, 2023 at 07:29:12PM +0530, Souradeep Chowdhury wrote:
>>>> The DCC is a DMA Engine designed to capture and store data
>>>> during system crash or software triggers. The DCC operates
>>>> based on user inputs via the debugfs interface. The user gives
>>>> addresses as inputs and these addresses are stored in the
>>>> dcc sram. In case of a system crash or a manual software
>>>> trigger by the user through the debugfs interface,
>>>> the dcc captures and stores the values at these addresses.
>>>> This patch contains the driver which has all the methods
>>>> pertaining to the debugfs interface, auxiliary functions to
>>>> support all the four fundamental operations of dcc namely
>>>> read, write, read/modify/write and loop. The probe method
>>>> here instantiates all the resources necessary for dcc to
>>>> operate mainly the dedicated dcc sram where it stores the
>>>> values. The DCC driver can be used for debugging purposes
>>>> without going for a reboot since it can perform software
>>>> triggers as well based on user inputs.
>>>
>>> You have 72 columns, why not use them all please?
>>>
>>>> +// SPDX-License-Identifier: GPL-2.0-only
>>>> +/*
>>>> + * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
>>>> + * Copyright (c) 2022, Qualcomm Innovation Center, Inc. All rights reserved.
>>>
>>> It is now 2023 :)
>>
>> Ack
>>
>>>
>>>
>>>
>>>
>>>> + */
>>>> +
>>>> +#include <linux/bitfield.h>
>>>> +#include <linux/bitops.h>
>>>> +#include <linux/debugfs.h>
>>>> +#include <linux/delay.h>
>>>> +#include <linux/fs.h>
>>>> +#include <linux/io.h>
>>>> +#include <linux/iopoll.h>
>>>> +#include <linux/miscdevice.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/of.h>
>>>> +#include <linux/of_device.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/slab.h>
>>>> +#include <linux/uaccess.h>
>>>> +
>>>> +#define STATUS_READY_TIMEOUT		5000  /* microseconds */
>>>> +
>>>> +#define DCC_SRAM_NODE "dcc_sram"
>>>
>>> You only use this once, why is a #define needed?
>>
>> This is as per the comment on version 1 of the patch series on DCC
>>
>> https://lore.kernel.org/linux-arm-kernel/YElUCaBUOx7hEuIh@builder.lan/
>>
>> "kzalloc + strlcpy can be replaced by kstrdup(), but that said...all this
>> does seems to be to copy a const string to the heap and lugging it
>> around. Use a define instead."
> 
> But as you are not doing any of that here, just using the string in the
> one place it is needed is the same thing :)

Ack

> 
>>>> +static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
>>>> +{
>>>> +	int i;
>>>> +	char list_num[10];
>>>> +	struct dentry *list;
>>>> +	struct device *dev = drvdata->dev;
>>>> +
>>>> +	drvdata->dbg_dir = debugfs_create_dir(dev_name(dev), NULL);
>>>
>>> You are creating a directory at the root of debugfs with just your
>>> device name?  While that will work, that feels very odd.  Please use a
>>> subdirectory.
>>
>> This is as per the comment on v17 of the patch series on DCC
>>
>> https://lore.kernel.org/linux-arm-kernel/6693993c-bd81-c974-a903-52a62bfec606@ieee.org/
>>
>> "You never remove this dcc_dbg directory.  Why not?
>>
>> And since you don't, dcc_dbg could just be a local
>> variable here rather than being a global.  But it
>> seems to me this is the root directory you want to
>> remove when you're done."
> 
> But that's not the issue.  The issue is that you are putting into
> /sys/kernel/debug/ a flat namespace of all of your devices.  Is that
> really what you want?  If so, why do you think this will never conflict
> with any other device in the system?

Since we are going by the dev_name here which also contains the address
as per the example in the yaml binding, this will not conflict with 
other dev_names in the system.

> 
>>>> +	if (IS_ERR(drvdata->dbg_dir)) {
>>>> +		pr_err("can't create debugfs dir\n");
>>>
>>> There is no need to ever check the return value of a debugfs call.
>>>
>>> Nor do you really ever even need to save off the dentry here, just look
>>> it up when you need to remove it.
>>
>> Ack
>>
>>>
>>>> +		return;
>>>> +	}
>>>> +
>>>> +	for (i = 0; i <= drvdata->nr_link_list; i++) {
>>>> +		sprintf(list_num, "%d", i);
>>>> +		list = debugfs_create_dir(list_num, drvdata->dbg_dir);
>>>> +		debugfs_create_file("enable", 0600, list, drvdata, &enable_fops);
>>>> +		debugfs_create_file("config", 0600, list, drvdata, &config_fops);
>>>> +	}
>>>> +
>>>> +	debugfs_create_file("trigger", 0200, drvdata->dbg_dir, drvdata, &trigger_fops);
>>>> +	debugfs_create_file("ready", 0400, drvdata->dbg_dir, drvdata, &ready_fops);
>>>> +	debugfs_create_file("config_reset", 0200, drvdata->dbg_dir,
>>>> +			    drvdata, &config_reset_fops);
>>>
>>> This really looks like you are using debugfs to control the device, not
>>> just for debugging information.  How are you going to be able to use the
>>> device in a system that has debugfs disabled?
>>
>> As per upstream discussions it was decided that debugfs will be a suitable
>> interface for DCC. More on this in the following link:-
>>
>> https://lore.kernel.org/linux-arm-kernel/20221228172825.r32vpphbdulaldvv@builder.lan/
> 
> debugfs is not a suitable interface for anything that is "real" as
> that's not what it is there for.  Most systems disable debugfs entirely
> (i.e. Android), or prevent any normal user from accessing it, so this
> api you are creating will not be able to be used by anyone.
> 
> debugfs is for debugging, not for anything that the system functionality
> relies on to work properly.

DCC is a debugging hardware which stores the values of the configured 
register address on a system crash on it's dedicated sram. These 
register addresses are configured by the user through the debugfs 
interface. Also on the platforms where debugfs is disabled there is an 
alternative of using bootconfig suggested to configure the register 
values during boot-time. There is an ongoing patch series for that as 
follows:-

https://lore.kernel.org/linux-arm-kernel/cover.1675054375.git.quic_schowdhu@quicinc.com/T/

> 
> Also, that was a v21 of the patch series, why did the numbering start
> over here at v1?

Ack. It was decided prior to merge this driver under drivers/soc/qcom 
but after discussions it was concluded that drivers/misc will be the 
suitable home for this driver. Will post subsequent versions as a 
continuation of the previous series for convenience.


> 
> thanks,
> 
> greg k-h

Re: [PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

[Greg Kroah-Hartman]

On Mon, Apr 17, 2023 at 12:26:23PM +0530, Souradeep Chowdhury wrote:
> On 4/17/2023 11:47 AM, Greg Kroah-Hartman wrote:
> > On Mon, Apr 17, 2023 at 11:31:46AM +0530, Souradeep Chowdhury wrote:
> > > On 4/15/2023 11:09 AM, Greg Kroah-Hartman wrote:
> > > > > +static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
> > > > > +{
> > > > > +	int i;
> > > > > +	char list_num[10];
> > > > > +	struct dentry *list;
> > > > > +	struct device *dev = drvdata->dev;
> > > > > +
> > > > > +	drvdata->dbg_dir = debugfs_create_dir(dev_name(dev), NULL);
> > > > 
> > > > You are creating a directory at the root of debugfs with just your
> > > > device name?  While that will work, that feels very odd.  Please use a
> > > > subdirectory.
> > > 
> > > This is as per the comment on v17 of the patch series on DCC
> > > 
> > > https://lore.kernel.org/linux-arm-kernel/6693993c-bd81-c974-a903-52a62bfec606@ieee.org/
> > > 
> > > "You never remove this dcc_dbg directory.  Why not?
> > > 
> > > And since you don't, dcc_dbg could just be a local
> > > variable here rather than being a global.  But it
> > > seems to me this is the root directory you want to
> > > remove when you're done."
> > 
> > But that's not the issue.  The issue is that you are putting into
> > /sys/kernel/debug/ a flat namespace of all of your devices.  Is that
> > really what you want?  If so, why do you think this will never conflict
> > with any other device in the system?
> 
> Since we are going by the dev_name here which also contains the address
> as per the example in the yaml binding, this will not conflict with other
> dev_names in the system.

That is not true at all.  dev_names are only unique per bus type.  There
is nothing preventing any other bus from using the same name for their
device as yours.

So please, for the sake of your own sanity, just create a directory and
dump all of your devices into it.  And for the sake of all of ours, as
making the root of debugfs full of random device names is a mess, don't
you think?  What would happen if all drivers did that?

> > > As per upstream discussions it was decided that debugfs will be a suitable
> > > interface for DCC. More on this in the following link:-
> > > 
> > > https://lore.kernel.org/linux-arm-kernel/20221228172825.r32vpphbdulaldvv@builder.lan/
> > 
> > debugfs is not a suitable interface for anything that is "real" as
> > that's not what it is there for.  Most systems disable debugfs entirely
> > (i.e. Android), or prevent any normal user from accessing it, so this
> > api you are creating will not be able to be used by anyone.
> > 
> > debugfs is for debugging, not for anything that the system functionality
> > relies on to work properly.
> 
> DCC is a debugging hardware which stores the values of the configured
> register address on a system crash on it's dedicated sram. These register
> addresses are configured by the user through the debugfs interface. Also on
> the platforms where debugfs is disabled there is an alternative of using
> bootconfig suggested to configure the register values during boot-time.
> There is an ongoing patch series for that as follows:-
> 
> https://lore.kernel.org/linux-arm-kernel/cover.1675054375.git.quic_schowdhu@quicinc.com/T/

But again, debugfs is not even mounted in most systems, so how are they
going to interact with your hardware?  Restricting it to debugfs feels
very odd to me, but hey, it's your code, I guess you don't want anyone
to use it :)

good luck!

greg k-h

Re: [PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

[Souradeep Chowdhury]

On 4/17/2023 1:11 PM, Greg Kroah-Hartman wrote:
> On Mon, Apr 17, 2023 at 12:26:23PM +0530, Souradeep Chowdhury wrote:
>> On 4/17/2023 11:47 AM, Greg Kroah-Hartman wrote:
>>> On Mon, Apr 17, 2023 at 11:31:46AM +0530, Souradeep Chowdhury wrote:
>>>> On 4/15/2023 11:09 AM, Greg Kroah-Hartman wrote:
>>>>>> +static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
>>>>>> +{
>>>>>> +	int i;
>>>>>> +	char list_num[10];
>>>>>> +	struct dentry *list;
>>>>>> +	struct device *dev = drvdata->dev;
>>>>>> +
>>>>>> +	drvdata->dbg_dir = debugfs_create_dir(dev_name(dev), NULL);
>>>>>
>>>>> You are creating a directory at the root of debugfs with just your
>>>>> device name?  While that will work, that feels very odd.  Please use a
>>>>> subdirectory.
>>>>
>>>> This is as per the comment on v17 of the patch series on DCC
>>>>
>>>> https://lore.kernel.org/linux-arm-kernel/6693993c-bd81-c974-a903-52a62bfec606@ieee.org/
>>>>
>>>> "You never remove this dcc_dbg directory.  Why not?
>>>>
>>>> And since you don't, dcc_dbg could just be a local
>>>> variable here rather than being a global.  But it
>>>> seems to me this is the root directory you want to
>>>> remove when you're done."
>>>
>>> But that's not the issue.  The issue is that you are putting into
>>> /sys/kernel/debug/ a flat namespace of all of your devices.  Is that
>>> really what you want?  If so, why do you think this will never conflict
>>> with any other device in the system?
>>
>> Since we are going by the dev_name here which also contains the address
>> as per the example in the yaml binding, this will not conflict with other
>> dev_names in the system.
> 
> That is not true at all.  dev_names are only unique per bus type.  There
> is nothing preventing any other bus from using the same name for their
> device as yours.
> 
> So please, for the sake of your own sanity, just create a directory and
> dump all of your devices into it.  And for the sake of all of ours, as
> making the root of debugfs full of random device names is a mess, don't
> you think?  What would happen if all drivers did that?

Ack

> 
>>>> As per upstream discussions it was decided that debugfs will be a suitable
>>>> interface for DCC. More on this in the following link:-
>>>>
>>>> https://lore.kernel.org/linux-arm-kernel/20221228172825.r32vpphbdulaldvv@builder.lan/
>>>
>>> debugfs is not a suitable interface for anything that is "real" as
>>> that's not what it is there for.  Most systems disable debugfs entirely
>>> (i.e. Android), or prevent any normal user from accessing it, so this
>>> api you are creating will not be able to be used by anyone.
>>>
>>> debugfs is for debugging, not for anything that the system functionality
>>> relies on to work properly.
>>
>> DCC is a debugging hardware which stores the values of the configured
>> register address on a system crash on it's dedicated sram. These register
>> addresses are configured by the user through the debugfs interface. Also on
>> the platforms where debugfs is disabled there is an alternative of using
>> bootconfig suggested to configure the register values during boot-time.
>> There is an ongoing patch series for that as follows:-
>>
>> https://lore.kernel.org/linux-arm-kernel/cover.1675054375.git.quic_schowdhu@quicinc.com/T/
> 
> But again, debugfs is not even mounted in most systems, so how are they
> going to interact with your hardware?  Restricting it to debugfs feels
> very odd to me, but hey, it's your code, I guess you don't want anyone
> to use it :)
> 
> good luck!
> 
> greg k-h

Re: [PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

[kernel test robot]

Hi Souradeep,

kernel test robot noticed the following build warnings:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.3-rc7 next-20230417]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Souradeep-Chowdhury/dt-bindings-misc-qcom-dcc-Add-the-dtschema/20230414-220304
patch link:    https://lore.kernel.org/r/b1a9cbbcfefe133cc9047a71a2acdaa74239df29.1681480351.git.quic_schowdhu%40quicinc.com
patch subject: [PATCH V1 2/3] drivers: misc: dcc: Add driver support for Data Capture and Compare unit(DCC)
config: arm64-allmodconfig (https://download.01.org/0day-ci/archive/20230418/202304181327.0grVYsHS-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 9638da200e00bd069e6dd63604e14cbafede9324)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/f3f73f6008e1ebca6fba848e260b1f938d91be95
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Souradeep-Chowdhury/dt-bindings-misc-qcom-dcc-Add-the-dtschema/20230414-220304
        git checkout f3f73f6008e1ebca6fba848e260b1f938d91be95
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash drivers/misc/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304181327.0grVYsHS-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/misc/dcc.c:217:14: warning: variable 'ret' is used uninitialized whenever 'for' loop exits because its condition is false [-Wsometimes-uninitialized]
           for (i = 0; i < drvdata->nr_link_list; i++) {
                       ^~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/misc/dcc.c:238:9: note: uninitialized use occurs here
           return ret;
                  ^~~
   drivers/misc/dcc.c:217:14: note: remove the condition if it is always true
           for (i = 0; i < drvdata->nr_link_list; i++) {
                       ^~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/misc/dcc.c:190:9: note: initialize the variable 'ret' to silence this warning
           int ret;
                  ^
                   = 0
   1 warning generated.


vim +217 drivers/misc/dcc.c

   186	
   187	static int dcc_sw_trigger(struct dcc_drvdata *drvdata)
   188	{
   189		void __iomem *addr;
   190		int ret;
   191		int i;
   192		u32 status;
   193		u32 ll_cfg;
   194		u32 tmp_ll_cfg;
   195		u32 val;
   196	
   197		mutex_lock(&drvdata->mutex);
   198	
   199		for (i = 0; i < drvdata->nr_link_list; i++) {
   200			if (!test_bit(i, drvdata->enable_bitmap))
   201				continue;
   202			ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
   203			tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
   204			dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
   205			dcc_list_writel(drvdata, 1, i, DCC_LL_SW_TRIGGER);
   206			dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
   207		}
   208	
   209		addr = drvdata->base + DCC_STATUS(drvdata->mem_map_ver);
   210		if (readl_poll_timeout(addr, val, !FIELD_GET(DCC_STATUS_MASK, val),
   211				       1, STATUS_READY_TIMEOUT)) {
   212			dev_err(drvdata->dev, "DCC is busy after receiving sw trigger\n");
   213			ret = -EBUSY;
   214			goto out_unlock;
   215		}
   216	
 > 217		for (i = 0; i < drvdata->nr_link_list; i++) {
   218			if (!test_bit(i, drvdata->enable_bitmap))
   219				continue;
   220	
   221			status = dcc_list_readl(drvdata, i, DCC_LL_BUS_ACCESS_STATUS);
   222			if (!status)
   223				continue;
   224	
   225			dev_err(drvdata->dev, "Read access error for list %d err: 0x%x\n",
   226				i, status);
   227			ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
   228			tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
   229			dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
   230			dcc_list_writel(drvdata, DCC_STATUS_MASK, i, DCC_LL_BUS_ACCESS_STATUS);
   231			dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
   232			ret = -ENODATA;
   233			break;
   234		}
   235	
   236	out_unlock:
   237		mutex_unlock(&drvdata->mutex);
   238		return ret;
   239	}
   240	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

[PATCH V1 3/3] MAINTAINERS: Add the entry for DCC(Data Capture and Compare) driver support

[Souradeep Chowdhury]

Add the entries for all the files added as a part of driver support for
DCC(Data Capture and Compare).

Signed-off-by: Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Reviewed-by: Bjorn Andersson <andersson@kernel.org>
---
 MAINTAINERS | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index b4e9c5b..2071000 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5705,6 +5705,14 @@ W:	http://lists.twibble.org/mailman/listinfo/dc395x/
 F:	Documentation/scsi/dc395x.rst
 F:	drivers/scsi/dc395x.*
 
+DCC QTI DRIVER
+M:      Souradeep Chowdhury <quic_schowdhu@quicinc.com>
+L:      linux-arm-msm@vger.kernel.org
+S:      Maintained
+F:      Documentation/ABI/testing/debugfs-driver-dcc
+F:      Documentation/devicetree/bindings/misc/qcom,dcc.yaml
+F:      drivers/misc/dcc.c
+
 DCCP PROTOCOL
 L:	dccp@vger.kernel.org
 S:	Orphan
-- 
2.7.4