Date:   Sat, 26 Aug 2023 10:19:42 +0530
From:   Abhijit Gangurde <abhijit.gangurde@....com>
To:     <gregkh@...uxfoundation.org>, <masahiroy@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <Nipun.Gupta@....com>, <nikhil.agarwal@....com>,
        <puneet.gupta@....com>, <git@....com>, <michal.simek@....com>,
        Abhijit Gangurde <abhijit.gangurde@....com>,
        Nipun Gupta <nipun.gupta@....com>,
        "Pieter Jansen van Vuuren" <pieter.jansen-van-vuuren@....com>
Subject: [PATCH v4 3/5] cdx: add support for bus enable and disable

CDX bus needs to be disabled before updating/writing devices
in the FPGA. Once the devices are written, the bus shall be
rescanned. This change provides sysfs entry to enable/disable the
CDX bus.

Co-developed-by: Nipun Gupta <nipun.gupta@....com>
Signed-off-by: Nipun Gupta <nipun.gupta@....com>
Signed-off-by: Abhijit Gangurde <abhijit.gangurde@....com>
Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@....com>
Tested-by: Nikhil Agarwal <nikhil.agarwal@....com>
---
 Changes in v4:
 - Add sparse marking for lock around cdx_find_controller() function

 Changes in v3:
 - Use platform bus to locate controller

 Changes in v2:
 - Improve documentation
 - Split sysfs entry enable to enable and disable
 - sysfs entry enable and disable take bus number as an argument

 Documentation/ABI/testing/sysfs-bus-cdx | 27 +++++++
 drivers/cdx/cdx.c                       | 97 +++++++++++++++++++++++++
 drivers/cdx/controller/cdx_controller.c | 50 +++++++++++++
 drivers/cdx/controller/mc_cdx_pcol.h    | 54 ++++++++++++++
 drivers/cdx/controller/mcdi_functions.c | 24 ++++++
 drivers/cdx/controller/mcdi_functions.h | 18 +++++
 include/linux/cdx/cdx_bus.h             | 12 +++
 7 files changed, 282 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-cdx b/Documentation/ABI/testing/sysfs-bus-cdx
index 7af477f49998..04c8dfe7e201 100644
--- a/Documentation/ABI/testing/sysfs-bus-cdx
+++ b/Documentation/ABI/testing/sysfs-bus-cdx
@@ -11,6 +11,33 @@ Description:
 
 		  # echo 1 > /sys/bus/cdx/rescan
 
+What:		/sys/bus/cdx/enable
+Date:		July 2023
+Contact:	nipun.gupta@....com
+Description:
+		Writing bus number in hex to this file will attempt to enable
+		the CDX bus. The bus number for the cdx devices can be found
+		at /sys/bus/cdx/devices/cdx-BB:DD, where BB denotes the bus
+		number for the respective device.
+
+		For example ::
+
+		  # echo 00 > /sys/bus/cdx/enable
+
+What:		/sys/bus/cdx/disable
+Date:		July 2023
+Contact:	nipun.gupta@....com
+Description:
+		Writing bus number in hex to this file will attempt to disable
+		the CDX bus. CDX bus should be disabled before updating the
+		devices in FPGA. The bus number for the cdx devices can be
+		found at /sys/bus/cdx/devices/cdx-BB:DD, where BB denotes the
+		bus number for the respective device.
+
+		For example ::
+
+		  # echo 00 > /sys/bus/cdx/disable
+
 What:		/sys/bus/cdx/devices/.../vendor
 Date:		March 2023
 Contact:	nipun.gupta@....com
diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c
index cbfe9a2f3646..8da043756fa4 100644
--- a/drivers/cdx/cdx.c
+++ b/drivers/cdx/cdx.c
@@ -70,6 +70,10 @@
 #define CDX_DEFAULT_DMA_MASK	(~0ULL)
 #define MAX_CDX_CONTROLLERS 16
 
+#define CONTROLLER_ID(X)	\
+	(((X) & CDX_CONTROLLER_ID_MASK) >> CDX_CONTROLLER_ID_SHIFT)
+#define BUS_ID(X) ((X) & CDX_BUS_NUM_MASK)
+
 /* IDA for CDX controllers registered with the CDX bus */
 static DEFINE_IDA(cdx_controller_ida);
 /* Lock to protect controller ops */
@@ -384,6 +388,97 @@ static struct attribute *cdx_dev_attrs[] = {
 };
 ATTRIBUTE_GROUPS(cdx_dev);
 
+/* Must be called with cdx_controller_lock acquired.
+ */
+static struct cdx_controller *cdx_find_controller(u8 controller_id)
+		__must_hold(&cdx_controller_lock)
+{
+	struct cdx_controller *cdx;
+	struct platform_device *pd;
+	struct device_node *np;
+
+	for_each_compatible_node(np, NULL, compat_node_name) {
+		if (!np)
+			return NULL;
+
+		pd = of_find_device_by_node(np);
+		if (!pd)
+			return NULL;
+
+		cdx = platform_get_drvdata(pd);
+		if (cdx && cdx->controller_registered && cdx->id == controller_id) {
+			put_device(&pd->dev);
+			return cdx;
+		}
+
+		put_device(&pd->dev);
+	}
+
+	return NULL;
+}
+
+static ssize_t enable_store(const struct bus_type *bus,
+			    const char *buf, size_t count)
+{
+	unsigned long controller_id;
+	struct cdx_controller *cdx;
+	u8 bus_id;
+	int ret;
+
+	if (kstrtou8(buf, 16, &bus_id))
+		return -EINVAL;
+
+	controller_id = CONTROLLER_ID(bus_id);
+	bus_id = BUS_ID(bus_id);
+
+	mutex_lock(&cdx_controller_lock);
+
+	cdx = cdx_find_controller(controller_id);
+	if (cdx)
+		if (cdx->ops->bus_enable)
+			ret = cdx->ops->bus_enable(cdx, bus_id);
+		else
+			ret = -EOPNOTSUPP;
+	else
+		ret = -EINVAL;
+
+	mutex_unlock(&cdx_controller_lock);
+
+	return ret < 0 ? ret : count;
+}
+static BUS_ATTR_WO(enable);
+
+static ssize_t disable_store(const struct bus_type *bus,
+			     const char *buf, size_t count)
+{
+	unsigned long controller_id;
+	struct cdx_controller *cdx;
+	u8 bus_id;
+	int ret;
+
+	if (kstrtou8(buf, 16, &bus_id))
+		return -EINVAL;
+
+	controller_id = CONTROLLER_ID(bus_id);
+	bus_id = BUS_ID(bus_id);
+
+	mutex_lock(&cdx_controller_lock);
+
+	cdx = cdx_find_controller(controller_id);
+	if (cdx)
+		if (cdx->ops->bus_disable)
+			ret = cdx->ops->bus_disable(cdx, bus_id);
+		else
+			ret = -EOPNOTSUPP;
+	else
+		ret = -EINVAL;
+
+	mutex_unlock(&cdx_controller_lock);
+
+	return ret < 0 ? ret : count;
+}
+static BUS_ATTR_WO(disable);
+
 static ssize_t rescan_store(const struct bus_type *bus,
 			    const char *buf, size_t count)
 {
@@ -426,6 +521,8 @@ static ssize_t rescan_store(const struct bus_type *bus,
 static BUS_ATTR_WO(rescan);
 
 static struct attribute *cdx_bus_attrs[] = {
+	&bus_attr_enable.attr,
+	&bus_attr_disable.attr,
 	&bus_attr_rescan.attr,
 	NULL,
 };
diff --git a/drivers/cdx/controller/cdx_controller.c b/drivers/cdx/controller/cdx_controller.c
index dc52f95f8978..2e4725c872d0 100644
--- a/drivers/cdx/controller/cdx_controller.c
+++ b/drivers/cdx/controller/cdx_controller.c
@@ -32,6 +32,42 @@ static const struct cdx_mcdi_ops mcdi_ops = {
 	.mcdi_request = cdx_mcdi_request,
 };
 
+static int cdx_bus_enable(struct cdx_controller *cdx, u8 bus_num)
+{
+	int ret;
+
+	if (test_bit(bus_num, cdx->bus_state))
+		return 0;
+
+	ret = cdx_mcdi_bus_enable(cdx->priv, bus_num);
+	if (!ret)
+		set_bit(bus_num, cdx->bus_state);
+
+	return ret;
+}
+
+static int cdx_bus_disable(struct cdx_controller *cdx, u8 bus_num)
+{
+	int ret;
+
+	if (!test_bit(bus_num, cdx->bus_state))
+		return 0;
+
+	ret = cdx_mcdi_bus_disable(cdx->priv, bus_num);
+	if (!ret)
+		clear_bit(bus_num, cdx->bus_state);
+
+	return ret;
+}
+
+static void cdx_bus_disable_all(struct cdx_controller *cdx)
+{
+	u8 bus_num;
+
+	for_each_set_bit(bus_num, cdx->bus_state, MAX_CDX_BUSES)
+		cdx_bus_disable(cdx, bus_num);
+}
+
 void cdx_rpmsg_post_probe(struct cdx_controller *cdx)
 {
 	/* Register CDX controller with CDX bus driver */
@@ -42,6 +78,7 @@ void cdx_rpmsg_post_probe(struct cdx_controller *cdx)
 void cdx_rpmsg_pre_remove(struct cdx_controller *cdx)
 {
 	cdx_unregister_controller(cdx);
+	cdx_bus_disable_all(cdx);
 	cdx_mcdi_wait_for_quiescence(cdx->priv, MCDI_RPC_TIMEOUT);
 }
 
@@ -80,11 +117,22 @@ static int cdx_scan_devices(struct cdx_controller *cdx)
 	for (bus_num = 0; bus_num < num_cdx_bus; bus_num++) {
 		u8 num_cdx_dev;
 
+		ret = cdx_bus_enable(cdx, bus_num);
+		if (ret && ret != -EALREADY) {
+			dev_err(cdx->dev,
+				"CDX bus %d enable failed: %d\n", bus_num, ret);
+			continue;
+		}
+
 		/* MCDI FW Read: Fetch the number of devices present */
 		ret = cdx_mcdi_get_num_devs(cdx_mcdi, bus_num);
 		if (ret < 0) {
 			dev_err(cdx->dev,
 				"Get devices on CDX bus %d failed: %d\n", bus_num, ret);
+			ret = cdx_bus_disable(cdx, bus_num);
+			if (ret)
+				dev_err(cdx->dev,
+					"CDX bus %d disable failed: %d\n", bus_num, ret);
 			continue;
 		}
 		num_cdx_dev = (u8)ret;
@@ -120,6 +168,8 @@ static int cdx_scan_devices(struct cdx_controller *cdx)
 }
 
 static struct cdx_ops cdx_ops = {
+	.bus_enable		= cdx_bus_enable,
+	.bus_disable	= cdx_bus_disable,
 	.scan		= cdx_scan_devices,
 	.dev_configure	= cdx_configure_device,
 };
diff --git a/drivers/cdx/controller/mc_cdx_pcol.h b/drivers/cdx/controller/mc_cdx_pcol.h
index 4ccb7b52951b..2de019406b57 100644
--- a/drivers/cdx/controller/mc_cdx_pcol.h
+++ b/drivers/cdx/controller/mc_cdx_pcol.h
@@ -455,6 +455,60 @@
 #define MC_CMD_CDX_BUS_GET_DEVICE_CONFIG_OUT_REQUESTER_ID_OFST			84
 #define MC_CMD_CDX_BUS_GET_DEVICE_CONFIG_OUT_REQUESTER_ID_LEN			4
 
+/***********************************/
+/*
+ * MC_CMD_CDX_BUS_DOWN
+ * Asserting reset on the CDX bus causes all devices on the bus to be quiesced.
+ * DMA bus mastering is disabled and any pending DMA request are flushed. Once
+ * the response is returned, the devices are guaranteed to no longer issue DMA
+ * requests or raise MSI interrupts. Further device MMIO accesses may have
+ * undefined results. While the bus reset is asserted, any of the enumeration
+ * or device configuration MCDIs will fail with EAGAIN. It is only legal to
+ * reload the relevant PL region containing CDX devices if the corresponding CDX
+ * bus is in reset. Depending on the implementation, the firmware may or may
+ * not enforce this restriction and it is up to the caller to make sure this
+ * requirement is satisfied.
+ */
+#define MC_CMD_CDX_BUS_DOWN					0x4
+#define MC_CMD_CDX_BUS_DOWN_MSGSET			0x4
+
+/* MC_CMD_CDX_BUS_DOWN_IN msgrequest */
+#define MC_CMD_CDX_BUS_DOWN_IN_LEN			4
+/* Bus number to put in reset, in range 0 to BUS_COUNT-1 */
+#define MC_CMD_CDX_BUS_DOWN_IN_BUS_OFST		0
+#define MC_CMD_CDX_BUS_DOWN_IN_BUS_LEN		4
+
+/*
+ * MC_CMD_CDX_BUS_DOWN_OUT msgresponse: The bus is quiesced, no further
+ * upstream traffic for devices on this bus.
+ */
+#define MC_CMD_CDX_BUS_DOWN_OUT_LEN			0
+
+/***********************************/
+/*
+ * MC_CMD_CDX_BUS_UP
+ * After bus reset is de-asserted, devices are in a state which is functionally
+ * equivalent to each device having been reset with MC_CMD_CDX_DEVICE_RESET. In
+ * other words, device logic is reset in a hardware-specific way, MMIO accesses
+ * are forwarded to the device, DMA bus mastering is disabled and needs to be
+ * re-enabled with MC_CMD_CDX_DEVICE_DMA_ENABLE once the driver is ready to
+ * start servicing DMA. If the underlying number of devices or device resources
+ * changed (e.g. if PL was reloaded) while the bus was in reset, the bus driver
+ * is expected to re-enumerate the bus. Returns EALREADY if the bus was already
+ * up before the call.
+ */
+#define MC_CMD_CDX_BUS_UP					0x5
+#define MC_CMD_CDX_BUS_UP_MSGSET			0x5
+
+/* MC_CMD_CDX_BUS_UP_IN msgrequest */
+#define MC_CMD_CDX_BUS_UP_IN_LEN			4
+/* Bus number to take out of reset, in range 0 to BUS_COUNT-1 */
+#define MC_CMD_CDX_BUS_UP_IN_BUS_OFST		0
+#define MC_CMD_CDX_BUS_UP_IN_BUS_LEN		4
+
+/* MC_CMD_CDX_BUS_UP_OUT msgresponse: The bus can now be enumerated. */
+#define MC_CMD_CDX_BUS_UP_OUT_LEN			0
+
 /***********************************/
 /*
  * MC_CMD_CDX_DEVICE_RESET
diff --git a/drivers/cdx/controller/mcdi_functions.c b/drivers/cdx/controller/mcdi_functions.c
index 0158f26533dd..0e1e35d91242 100644
--- a/drivers/cdx/controller/mcdi_functions.c
+++ b/drivers/cdx/controller/mcdi_functions.c
@@ -124,6 +124,30 @@ int cdx_mcdi_get_dev_config(struct cdx_mcdi *cdx,
 	return 0;
 }
 
+int cdx_mcdi_bus_enable(struct cdx_mcdi *cdx, u8 bus_num)
+{
+	MCDI_DECLARE_BUF(inbuf, MC_CMD_CDX_BUS_UP_IN_LEN);
+	int ret;
+
+	MCDI_SET_DWORD(inbuf, CDX_BUS_UP_IN_BUS, bus_num);
+	ret = cdx_mcdi_rpc(cdx, MC_CMD_CDX_BUS_UP, inbuf, sizeof(inbuf),
+			   NULL, 0, NULL);
+
+	return ret;
+}
+
+int cdx_mcdi_bus_disable(struct cdx_mcdi *cdx, u8 bus_num)
+{
+	MCDI_DECLARE_BUF(inbuf, MC_CMD_CDX_BUS_DOWN_IN_LEN);
+	int ret;
+
+	MCDI_SET_DWORD(inbuf, CDX_BUS_DOWN_IN_BUS, bus_num);
+	ret = cdx_mcdi_rpc(cdx, MC_CMD_CDX_BUS_DOWN, inbuf, sizeof(inbuf),
+			   NULL, 0, NULL);
+
+	return ret;
+}
+
 int cdx_mcdi_reset_device(struct cdx_mcdi *cdx, u8 bus_num, u8 dev_num)
 {
 	MCDI_DECLARE_BUF(inbuf, MC_CMD_CDX_DEVICE_RESET_IN_LEN);
diff --git a/drivers/cdx/controller/mcdi_functions.h b/drivers/cdx/controller/mcdi_functions.h
index 7440ace5539a..28973d5ec3ab 100644
--- a/drivers/cdx/controller/mcdi_functions.h
+++ b/drivers/cdx/controller/mcdi_functions.h
@@ -47,6 +47,24 @@ int cdx_mcdi_get_dev_config(struct cdx_mcdi *cdx,
 			    u8 bus_num, u8 dev_num,
 			    struct cdx_dev_params *dev_params);
 
+/**
+ * cdx_mcdi_bus_enable - Enable CDX bus represented by bus_num
+ * @cdx: pointer to MCDI interface.
+ * @bus_num: Bus number.
+ *
+ * Return: 0 on success, <0 on failure
+ */
+int cdx_mcdi_bus_enable(struct cdx_mcdi *cdx, u8 bus_num);
+
+/**
+ * cdx_mcdi_bus_disable - Disable CDX bus represented by bus_num
+ * @cdx: pointer to MCDI interface.
+ * @bus_num: Bus number.
+ *
+ * Return: 0 on success, <0 on failure
+ */
+int cdx_mcdi_bus_disable(struct cdx_mcdi *cdx, u8 bus_num);
+
 /**
  * cdx_mcdi_reset_device - Reset cdx device represented by bus_num:dev_num
  * @cdx: pointer to MCDI interface.
diff --git a/include/linux/cdx/cdx_bus.h b/include/linux/cdx/cdx_bus.h
index 82c27b8c94e1..ac715bc84315 100644
--- a/include/linux/cdx/cdx_bus.h
+++ b/include/linux/cdx/cdx_bus.h
@@ -16,6 +16,8 @@
 #define MAX_CDX_DEV_RESOURCES	4
 #define CDX_CONTROLLER_ID_SHIFT 4
 #define CDX_BUS_NUM_MASK 0xF
+#define CDX_CONTROLLER_ID_MASK	0xF0
+#define MAX_CDX_BUSES			(CDX_BUS_NUM_MASK + 1)
 
 /* Forward declaration for CDX controller */
 struct cdx_controller;
@@ -28,6 +30,10 @@ struct cdx_device_config {
 	u8 type;
 };
 
+typedef int (*cdx_bus_enable_cb)(struct cdx_controller *cdx, u8 bus_num);
+
+typedef int (*cdx_bus_disable_cb)(struct cdx_controller *cdx, u8 bus_num);
+
 typedef int (*cdx_scan_cb)(struct cdx_controller *cdx);
 
 typedef int (*cdx_dev_configure_cb)(struct cdx_controller *cdx,
@@ -49,11 +55,15 @@ typedef int (*cdx_dev_configure_cb)(struct cdx_controller *cdx,
 
 /**
  * struct cdx_ops - Callbacks supported by CDX controller.
+ * @bus_enable: enable bus on the controller
+ * @bus_disable: disable bus on the controller
  * @scan: scan the devices on the controller
  * @dev_configure: configuration like reset, master_enable,
  *		   msi_config etc for a CDX device
  */
 struct cdx_ops {
+	cdx_bus_enable_cb bus_enable;
+	cdx_bus_disable_cb bus_disable;
 	cdx_scan_cb scan;
 	cdx_dev_configure_cb dev_configure;
 };
@@ -64,6 +74,7 @@ struct cdx_ops {
  * @priv: private data
  * @id: Controller ID
  * @controller_registered: controller registered with bus
+ * @bus_state: state of the buses(enabled/disabled)
  * @ops: CDX controller ops
  */
 struct cdx_controller {
@@ -71,6 +82,7 @@ struct cdx_controller {
 	void *priv;
 	u32 id;
 	bool controller_registered;
+	DECLARE_BITMAP(bus_state, MAX_CDX_BUSES);
 	struct cdx_ops *ops;
 };
 
-- 
2.25.1

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