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From:   Nipun Gupta <nipun.gupta@amd.com>
To:     <gregkh@linuxfoundation.org>, <alex.williamson@redhat.com>,
        <linux-kernel@vger.kernel.org>
CC:     <git@amd.com>, <pieter.jansen-van-vuuren@amd.com>,
        <nikhil.agarwal@amd.com>, <michal.simek@amd.com>,
        <abhijit.gangurde@amd.com>, <srivatsa@csail.mit.edu>,
        Nipun Gupta <nipun.gupta@amd.com>
Subject: [PATCH v8 1/3] cdx: add support for bus mastering
Date:   Fri, 15 Sep 2023 10:24:21 +0530
Message-ID: <20230915045423.31630-1-nipun.gupta@amd.com>
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Introduce cdx_set_master() and cdx_clear_master() APIs to support
enable and disable of bus mastering. Drivers need to use these APIs to
enable/disable DMAs from the CDX devices.

Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
---

Changes v7->v8:
- Fix a comment in cdx_mcdi_ctrl_flag_set()

Changes v6->v7:
- None

Changes v5->v6:
- change cdx_clear_master() to int return type

Changes v4->v5:
- No change in this patch, patch 2/3 and patch 3/3 are updated

Changes v3->v4:
- Added user of the Bus master enable and disable APIs in patch 2/2.
  There is no change in this patch.

Changes v2->v3:
- Changed return value from EOPNOTSUPP to -EOPNOTSUPP in
  cdx_set_master()

Changes v1->v2:
- Replace bme with bus_master_enable
- Added check for dev_configure API callback
- remove un-necessary error prints
- changed conditional to if-else
- updated commit message to use 72 columns

 drivers/cdx/cdx.c                       | 32 ++++++++++++++
 drivers/cdx/controller/cdx_controller.c |  4 ++
 drivers/cdx/controller/mcdi_functions.c | 58 +++++++++++++++++++++++++
 drivers/cdx/controller/mcdi_functions.h | 13 ++++++
 include/linux/cdx/cdx_bus.h             | 18 ++++++++
 5 files changed, 125 insertions(+)

diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c
index d2cad4c670a0..9efb7584f952 100644
--- a/drivers/cdx/cdx.c
+++ b/drivers/cdx/cdx.c
@@ -182,6 +182,38 @@ cdx_match_id(const struct cdx_device_id *ids, struct cdx_device *dev)
 	return NULL;
 }
 
+int cdx_set_master(struct cdx_device *cdx_dev)
+{
+	struct cdx_controller *cdx = cdx_dev->cdx;
+	struct cdx_device_config dev_config;
+	int ret = -EOPNOTSUPP;
+
+	dev_config.type = CDX_DEV_BUS_MASTER_CONF;
+	dev_config.bus_master_enable = true;
+	if (cdx->ops->dev_configure)
+		ret = cdx->ops->dev_configure(cdx, cdx_dev->bus_num,
+					      cdx_dev->dev_num, &dev_config);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cdx_set_master);
+
+int cdx_clear_master(struct cdx_device *cdx_dev)
+{
+	struct cdx_controller *cdx = cdx_dev->cdx;
+	struct cdx_device_config dev_config;
+	int ret = -EOPNOTSUPP;
+
+	dev_config.type = CDX_DEV_BUS_MASTER_CONF;
+	dev_config.bus_master_enable = false;
+	if (cdx->ops->dev_configure)
+		ret = cdx->ops->dev_configure(cdx, cdx_dev->bus_num,
+					      cdx_dev->dev_num, &dev_config);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cdx_clear_master);
+
 /**
  * cdx_bus_match - device to driver matching callback
  * @dev: the cdx device to match against
diff --git a/drivers/cdx/controller/cdx_controller.c b/drivers/cdx/controller/cdx_controller.c
index dc52f95f8978..39aa569d8e07 100644
--- a/drivers/cdx/controller/cdx_controller.c
+++ b/drivers/cdx/controller/cdx_controller.c
@@ -55,6 +55,10 @@ static int cdx_configure_device(struct cdx_controller *cdx,
 	case CDX_DEV_RESET_CONF:
 		ret = cdx_mcdi_reset_device(cdx->priv, bus_num, dev_num);
 		break;
+	case CDX_DEV_BUS_MASTER_CONF:
+		ret = cdx_mcdi_bus_master_enable(cdx->priv, bus_num, dev_num,
+						 dev_config->bus_master_enable);
+		break;
 	default:
 		ret = -EINVAL;
 	}
diff --git a/drivers/cdx/controller/mcdi_functions.c b/drivers/cdx/controller/mcdi_functions.c
index 0158f26533dd..6acd8fea4586 100644
--- a/drivers/cdx/controller/mcdi_functions.c
+++ b/drivers/cdx/controller/mcdi_functions.c
@@ -137,3 +137,61 @@ int cdx_mcdi_reset_device(struct cdx_mcdi *cdx, u8 bus_num, u8 dev_num)
 
 	return ret;
 }
+
+static int cdx_mcdi_ctrl_flag_get(struct cdx_mcdi *cdx, u8 bus_num,
+				  u8 dev_num, u32 *flags)
+{
+	MCDI_DECLARE_BUF(inbuf, MC_CMD_CDX_DEVICE_CONTROL_GET_IN_LEN);
+	MCDI_DECLARE_BUF(outbuf, MC_CMD_CDX_DEVICE_CONTROL_GET_OUT_LEN);
+	size_t outlen;
+	int ret;
+
+	MCDI_SET_DWORD(inbuf, CDX_DEVICE_CONTROL_GET_IN_BUS, bus_num);
+	MCDI_SET_DWORD(inbuf, CDX_DEVICE_CONTROL_GET_IN_DEVICE, dev_num);
+	ret = cdx_mcdi_rpc(cdx, MC_CMD_CDX_DEVICE_CONTROL_GET, inbuf,
+			   sizeof(inbuf), outbuf, sizeof(outbuf), &outlen);
+	if (ret)
+		return ret;
+
+	if (outlen != MC_CMD_CDX_DEVICE_CONTROL_GET_OUT_LEN)
+		return -EIO;
+
+	*flags = MCDI_DWORD(outbuf, CDX_DEVICE_CONTROL_GET_OUT_FLAGS);
+
+	return 0;
+}
+
+static int cdx_mcdi_ctrl_flag_set(struct cdx_mcdi *cdx, u8 bus_num,
+				  u8 dev_num, bool enable, int bit_pos)
+{
+	MCDI_DECLARE_BUF(inbuf, MC_CMD_CDX_DEVICE_CONTROL_SET_IN_LEN);
+	u32 flags;
+	int ret;
+
+	/*
+	 * Get flags and then set/reset bit at bit_pos according to
+	 * the input params.
+	 */
+	ret = cdx_mcdi_ctrl_flag_get(cdx, bus_num, dev_num, &flags);
+	if (ret)
+		return ret;
+
+	flags = flags & (u32)(~(BIT(bit_pos)));
+	if (enable)
+		flags |= (1 << bit_pos);
+
+	MCDI_SET_DWORD(inbuf, CDX_DEVICE_CONTROL_SET_IN_BUS, bus_num);
+	MCDI_SET_DWORD(inbuf, CDX_DEVICE_CONTROL_SET_IN_DEVICE, dev_num);
+	MCDI_SET_DWORD(inbuf, CDX_DEVICE_CONTROL_SET_IN_FLAGS, flags);
+	ret = cdx_mcdi_rpc(cdx, MC_CMD_CDX_DEVICE_CONTROL_SET, inbuf,
+			   sizeof(inbuf), NULL, 0, NULL);
+
+	return ret;
+}
+
+int cdx_mcdi_bus_master_enable(struct cdx_mcdi *cdx, u8 bus_num,
+			       u8 dev_num, bool enable)
+{
+	return cdx_mcdi_ctrl_flag_set(cdx, bus_num, dev_num, enable,
+			MC_CMD_CDX_DEVICE_CONTROL_SET_IN_BUS_MASTER_ENABLE_LBN);
+}
diff --git a/drivers/cdx/controller/mcdi_functions.h b/drivers/cdx/controller/mcdi_functions.h
index 7440ace5539a..a448d6581eb4 100644
--- a/drivers/cdx/controller/mcdi_functions.h
+++ b/drivers/cdx/controller/mcdi_functions.h
@@ -58,4 +58,17 @@ int cdx_mcdi_get_dev_config(struct cdx_mcdi *cdx,
 int cdx_mcdi_reset_device(struct cdx_mcdi *cdx,
 			  u8 bus_num, u8 dev_num);
 
+/**
+ * cdx_mcdi_bus_master_enable - Set/Reset bus mastering for cdx device
+ *				represented by bus_num:dev_num
+ * @cdx: pointer to MCDI interface.
+ * @bus_num: Bus number.
+ * @dev_num: Device number.
+ * @enable: Enable bus mastering if set, disable otherwise.
+ *
+ * Return: 0 on success, <0 on failure
+ */
+int cdx_mcdi_bus_master_enable(struct cdx_mcdi *cdx, u8 bus_num,
+			       u8 dev_num, bool enable);
+
 #endif /* CDX_MCDI_FUNCTIONS_H */
diff --git a/include/linux/cdx/cdx_bus.h b/include/linux/cdx/cdx_bus.h
index bead71b7bc73..8320ec3b9e37 100644
--- a/include/linux/cdx/cdx_bus.h
+++ b/include/linux/cdx/cdx_bus.h
@@ -21,11 +21,13 @@
 struct cdx_controller;
 
 enum {
+	CDX_DEV_BUS_MASTER_CONF,
 	CDX_DEV_RESET_CONF,
 };
 
 struct cdx_device_config {
 	u8 type;
+	bool bus_master_enable;
 };
 
 typedef int (*cdx_scan_cb)(struct cdx_controller *cdx);
@@ -170,4 +172,20 @@ extern struct bus_type cdx_bus_type;
  */
 int cdx_dev_reset(struct device *dev);
 
+/**
+ * cdx_set_master - enables bus-mastering for CDX device
+ * @cdx_dev: the CDX device to enable
+ *
+ * Return: 0 for success, -errno on failure
+ */
+int cdx_set_master(struct cdx_device *cdx_dev);
+
+/**
+ * cdx_clear_master - disables bus-mastering for CDX device
+ * @cdx_dev: the CDX device to disable
+ *
+ * Return: 0 for success, -errno on failure
+ */
+int cdx_clear_master(struct cdx_device *cdx_dev);
+
 #endif /* _CDX_BUS_H_ */
-- 
2.17.1