scsi: ufs: Add a bsg endpoint that supports UPIUs

For now, just provide an API to allocate and remove ufs-bsg node. We
will use this framework to manage ufs devices by sending UPIU
transactions.

For the time being, implements an empty bsg_request() - will add some
more functionality in coming patches.

Nonetheless, we reveal here the protocol we are planning to use: UFS
Transport Protocol Transactions. UFS transactions consist of packets
called UFS Protocol Information Units (UPIU).

There are UPIU’s defined for UFS SCSI commands, responses, data in and
data out, task management, utility functions, vendor functions,
transaction synchronization and control, and more.

By using UPIUs, we get access to the most fine-grained internals of this
protocol, and able to communicate with the device in ways, that are
sometimes beyond the capacity of the ufs driver.

Moreover and as a result, our core structure - ufs_bsg_node has a pretty
lean structure: using upiu transactions that contains the outmost
detailed info, so we don't really need complex constructs to support it.

Signed-off-by: Avri Altman <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Bart Van Assche <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

Documentation/scsi/ufs.txt

···
 In this version of UFSHCD Query requests and power management
 functionality are not implemented.
 
+4. BSG Support
+------------------
+
+This transport driver supports exchanging UFS protocol information units
+(UPIUs) with a UFS device. Typically, user space will allocate
+struct ufs_bsg_request and struct ufs_bsg_reply (see ufs_bsg.h) as
+request_upiu and reply_upiu respectively.  Filling those UPIUs should
+be done in accordance with JEDEC spec UFS2.1 paragraph 10.7.
+*Caveat emptor*: The driver makes no further input validations and sends the
+UPIU to the device as it is.  Open the bsg device in /dev/ufs-bsg and
+send SG_IO with the applicable sg_io_v4:
+
+	io_hdr_v4.guard = 'Q';
+	io_hdr_v4.protocol = BSG_PROTOCOL_SCSI;
+	io_hdr_v4.subprotocol = BSG_SUB_PROTOCOL_SCSI_TRANSPORT;
+	io_hdr_v4.response = (__u64)reply_upiu;
+	io_hdr_v4.max_response_len = reply_len;
+	io_hdr_v4.request_len = request_len;
+	io_hdr_v4.request = (__u64)request_upiu;
+
 UFS Specifications can be found at,
 UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
 UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf

drivers/scsi/ufs/Kconfig

···
 
 	  Select this if you have UFS controller on Hisilicon chipset.
 	  If unsure, say N.
+
+config SCSI_UFS_BSG
+	bool "Universal Flash Storage BSG device node"
+	depends on SCSI_UFSHCD
+	select BLK_DEV_BSGLIB
+	help
+	  Universal Flash Storage (UFS) is SCSI transport specification for
+	  accessing flash storage on digital cameras, mobile phones and
+	  consumer electronic devices.
+	  A UFS controller communicates with a UFS device by exchanging
+	  UFS Protocol Information Units (UPIUs).
+	  UPIUs can not only be used as a transport layer for the SCSI protocol
+	  but are also used by the UFS native command set.
+	  This transport driver supports exchanging UFS protocol information units
+	  with a UFS device. See also the ufshcd driver, which is a SCSI driver
+	  that supports UFS devices.
+
+	  Select this if you need a bsg device node for your UFS controller.
+	  If unsure, say N.

drivers/scsi/ufs/Makefile

···
 obj-$(CONFIG_SCSI_UFS_DWC_TC_PLATFORM) += tc-dwc-g210-pltfrm.o ufshcd-dwc.o tc-dwc-g210.o
 obj-$(CONFIG_SCSI_UFS_QCOM) += ufs-qcom.o
 obj-$(CONFIG_SCSI_UFSHCD) += ufshcd-core.o
-ufshcd-core-objs := ufshcd.o ufs-sysfs.o
+ufshcd-core-y				+= ufshcd.o ufs-sysfs.o
+ufshcd-core-$(CONFIG_SCSI_UFS_BSG)	+= ufs_bsg.o
 obj-$(CONFIG_SCSI_UFSHCD_PCI) += ufshcd-pci.o
 obj-$(CONFIG_SCSI_UFSHCD_PLATFORM) += ufshcd-pltfrm.o
 obj-$(CONFIG_SCSI_UFS_HISI) += ufs-hisi.o

drivers/scsi/ufs/ufs_bsg.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * bsg endpoint that supports UPIUs
+ *
+ * Copyright (C) 2018 Western Digital Corporation
+ */
+#include "ufs_bsg.h"
+
+
+static int ufs_bsg_request(struct bsg_job *job)
+{
+	struct ufs_bsg_request *bsg_request = job->request;
+	struct ufs_bsg_reply *bsg_reply = job->reply;
+	int ret = -ENOTSUPP;
+
+	bsg_reply->reply_payload_rcv_len = 0;
+
+	/* Do Nothing for now */
+	dev_err(job->dev, "unsupported message_code 0x%x\n",
+		bsg_request->msgcode);
+
+	bsg_reply->result = ret;
+	job->reply_len = sizeof(struct ufs_bsg_reply) +
+			 bsg_reply->reply_payload_rcv_len;
+
+	bsg_job_done(job, ret, bsg_reply->reply_payload_rcv_len);
+
+	return ret;
+}
+
+/**
+ * ufs_bsg_remove - detach and remove the added ufs-bsg node
+ *
+ * Should be called when unloading the driver.
+ */
+void ufs_bsg_remove(struct ufs_hba *hba)
+{
+	struct device *bsg_dev = &hba->bsg_dev;
+
+	if (!hba->bsg_queue)
+		return;
+
+	bsg_unregister_queue(hba->bsg_queue);
+
+	device_del(bsg_dev);
+	put_device(bsg_dev);
+}
+
+static inline void ufs_bsg_node_release(struct device *dev)
+{
+	put_device(dev->parent);
+}
+
+/**
+ * ufs_bsg_probe - Add ufs bsg device node
+ * @hba: per adapter object
+ *
+ * Called during initial loading of the driver, and before scsi_scan_host.
+ */
+int ufs_bsg_probe(struct ufs_hba *hba)
+{
+	struct device *bsg_dev = &hba->bsg_dev;
+	struct Scsi_Host *shost = hba->host;
+	struct device *parent = &shost->shost_gendev;
+	struct request_queue *q;
+	int ret;
+
+	device_initialize(bsg_dev);
+
+	bsg_dev->parent = get_device(parent);
+	bsg_dev->release = ufs_bsg_node_release;
+
+	dev_set_name(bsg_dev, "ufs-bsg");
+
+	ret = device_add(bsg_dev);
+	if (ret)
+		goto out;
+
+	q = bsg_setup_queue(bsg_dev, dev_name(bsg_dev), ufs_bsg_request, 0);
+	if (IS_ERR(q)) {
+		ret = PTR_ERR(q);
+		goto out;
+	}
+
+	hba->bsg_queue = q;
+
+	return 0;
+
+out:
+	dev_err(bsg_dev, "fail to initialize a bsg dev %d\n", shost->host_no);
+	put_device(bsg_dev);
+	return ret;
+}

drivers/scsi/ufs/ufs_bsg.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2018 Western Digital Corporation
+ */
+#ifndef UFS_BSG_H
+#define UFS_BSG_H
+
+#include <linux/bsg-lib.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_host.h>
+
+#include "ufshcd.h"
+#include "ufs.h"
+
+#ifdef CONFIG_SCSI_UFS_BSG
+void ufs_bsg_remove(struct ufs_hba *hba);
+int ufs_bsg_probe(struct ufs_hba *hba);
+#else
+static inline void ufs_bsg_remove(struct ufs_hba *hba) {}
+static inline int ufs_bsg_probe(struct ufs_hba *hba) {return 0; }
+#endif
+
+#endif /* UFS_BSG_H */

drivers/scsi/ufs/ufshcd.c

···
 #include "ufs_quirks.h"
 #include "unipro.h"
 #include "ufs-sysfs.h"
+#include "ufs_bsg.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/ufs.h>
···
 			hba->clk_scaling.is_allowed = true;
 		}
 
+		ufs_bsg_probe(hba);
+
 		scsi_scan_host(hba->host);
 		pm_runtime_put_sync(hba->dev);
 	}
···
  */
 void ufshcd_remove(struct ufs_hba *hba)
 {
+	ufs_bsg_remove(hba);
 	ufs_sysfs_remove_nodes(hba->dev);
 	scsi_remove_host(hba->host);
 	/* disable interrupts */

drivers/scsi/ufs/ufshcd.h

···
 	struct rw_semaphore clk_scaling_lock;
 	struct ufs_desc_size desc_size;
 	atomic_t scsi_block_reqs_cnt;
+
+	struct device		bsg_dev;
+	struct request_queue	*bsg_queue;
 };
 
 /* Returns true if clocks can be gated. Otherwise false */

include/uapi/scsi/scsi_bsg_ufs.h

···
  * UFS Transport SGIO v4 BSG Message Support
  *
  * Copyright (C) 2011-2013 Samsung India Software Operations
+ * Copyright (C) 2018 Western Digital Corporation
  */
 #ifndef SCSI_BSG_UFS_H
 #define SCSI_BSG_UFS_H
···
 	union {
 		struct utp_upiu_cmd		sc;
 		struct utp_upiu_query		qr;
+		struct utp_upiu_query		tr;
+		/* use utp_upiu_query to host the 4 dwords of uic command */
+		struct utp_upiu_query		uc;
 	};
+};
+
+/* request (CDB) structure of the sg_io_v4 */
+struct ufs_bsg_request {
+	uint32_t msgcode;
+	struct utp_upiu_req upiu_req;
+};
+
+/* response (request sense data) structure of the sg_io_v4 */
+struct ufs_bsg_reply {
+	/*
+	 * The completion result. Result exists in two forms:
+	 * if negative, it is an -Exxx system errno value. There will
+	 * be no further reply information supplied.
+	 * else, it's the 4-byte scsi error result, with driver, host,
+	 * msg and status fields. The per-msgcode reply structure
+	 * will contain valid data.
+	 */
+	uint32_t result;
+
+	/* If there was reply_payload, how much was received? */
+	uint32_t reply_payload_rcv_len;
+
+	struct utp_upiu_req upiu_rsp;
 };
 #endif /* UFS_BSG_H */