misc: bcm-vk: add ttyVK support

Add ttyVK support to driver to allow console access to VK card from host.

Device node will be in the follow form /dev/bcm-vk.x_ttyVKy where:
x is the instance of the VK card
y is the tty device number on the VK card

Acked-by: Olof Johansson <[e-mail]>
Signed-off-by: Scott Branden <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/bcm-vk/Makefile

···
 bcm_vk-objs := \
 	bcm_vk_dev.o \
 	bcm_vk_msg.o \
-	bcm_vk_sg.o
+	bcm_vk_sg.o \
+	bcm_vk_tty.o
 

drivers/misc/bcm-vk/bcm_vk.h

···
 
 #include <linux/atomic.h>
 #include <linux/firmware.h>
+#include <linux/irq.h>
 #include <linux/kref.h>
 #include <linux/miscdevice.h>
 #include <linux/mutex.h>
 #include <linux/pci.h>
 #include <linux/poll.h>
 #include <linux/sched/signal.h>
+#include <linux/tty.h>
 #include <linux/uaccess.h>
 #include <uapi/linux/misc/bcm_vk.h>
 
···
 #define CODEPUSH_BOOT2_ENTRY		0x60000000
 
 #define BAR_CARD_STATUS			0x410
+/* CARD_STATUS definitions */
+#define CARD_STATUS_TTYVK0_READY	BIT(0)
+#define CARD_STATUS_TTYVK1_READY	BIT(1)
 
 #define BAR_BOOT1_STDALONE_PROGRESS	0x420
 #define BOOT1_STDALONE_SUCCESS		(BIT(13) | BIT(14))
···
 
 #define BCM_VK_NUM_TTY 2
 
+struct bcm_vk_tty {
+	struct tty_port port;
+	u32 to_offset;	/* bar offset to use */
+	u32 to_size;	/* to VK buffer size */
+	u32 wr;		/* write offset shadow */
+	u32 from_offset;	/* bar offset to use */
+	u32 from_size;	/* from VK buffer size */
+	u32 rd;		/* read offset shadow */
+	pid_t pid;
+	bool irq_enabled;
+	bool is_opened;		/* tracks tty open/close */
+};
+
 /* VK device max power state, supports 3, full, reduced and low */
 #define MAX_OPP 3
 #define MAX_CARD_INFO_TAG_SIZE 64
···
 	struct mutex mutex;
 	struct miscdevice miscdev;
 	int devid; /* dev id allocated */
+
+	struct tty_driver *tty_drv;
+	struct timer_list serial_timer;
+	struct bcm_vk_tty tty[BCM_VK_NUM_TTY];
+	struct workqueue_struct *tty_wq_thread;
+	struct work_struct tty_wq_work;
 
 	/* Reference-counting to handle file operations */
 	struct kref kref;
···
 void bcm_vk_release_data(struct kref *kref);
 irqreturn_t bcm_vk_msgq_irqhandler(int irq, void *dev_id);
 irqreturn_t bcm_vk_notf_irqhandler(int irq, void *dev_id);
+irqreturn_t bcm_vk_tty_irqhandler(int irq, void *dev_id);
 int bcm_vk_msg_init(struct bcm_vk *vk);
 void bcm_vk_msg_remove(struct bcm_vk *vk);
 void bcm_vk_drain_msg_on_reset(struct bcm_vk *vk);
···
 			     const pid_t pid, const u32 q_num);
 void bcm_to_v_q_doorbell(struct bcm_vk *vk, u32 q_num, u32 db_val);
 int bcm_vk_auto_load_all_images(struct bcm_vk *vk);
+int bcm_vk_tty_init(struct bcm_vk *vk, char *name);
+void bcm_vk_tty_exit(struct bcm_vk *vk);
+void bcm_vk_tty_terminate_tty_user(struct bcm_vk *vk);
 void bcm_vk_hb_init(struct bcm_vk *vk);
 void bcm_vk_hb_deinit(struct bcm_vk *vk);
 void bcm_vk_handle_notf(struct bcm_vk *vk);

drivers/misc/bcm-vk/bcm_vk_dev.c

···
 			}
 		}
 	}
+	bcm_vk_tty_terminate_tty_user(vk);
 	spin_unlock(&vk->ctx_lock);
 }
 
···
 	}
 	vk->num_irqs++;
 
+	for (i = 0;
+	     (i < VK_MSIX_TTY_MAX) && (vk->num_irqs < irq);
+	     i++, vk->num_irqs++) {
+		err = devm_request_irq(dev, pci_irq_vector(pdev, vk->num_irqs),
+				       bcm_vk_tty_irqhandler,
+				       IRQF_SHARED, DRV_MODULE_NAME, vk);
+		if (err) {
+			dev_err(dev, "failed request tty IRQ %d for MSIX %d\n",
+				pdev->irq + vk->num_irqs, vk->num_irqs + 1);
+			goto err_irq;
+		}
+		vk->tty[i].irq_enabled = true;
+	}
+
 	id = ida_simple_get(&bcm_vk_ida, 0, 0, GFP_KERNEL);
 	if (id < 0) {
 		err = id;
···
 		goto err_destroy_workqueue;
 	}
 
+	snprintf(name, sizeof(name), KBUILD_MODNAME ".%d_ttyVK", id);
+	err = bcm_vk_tty_init(vk, name);
+	if (err)
+		goto err_unregister_panic_notifier;
+
 	/*
 	 * lets trigger an auto download.  We don't want to do it serially here
 	 * because at probing time, it is not supposed to block for a long time.
···
 	if (auto_load) {
 		if ((boot_status & BOOT_STATE_MASK) == BROM_RUNNING) {
 			if (bcm_vk_trigger_autoload(vk))
-				goto err_unregister_panic_notifier;
+				goto err_bcm_vk_tty_exit;
 		} else {
 			dev_err(dev,
 				"Auto-load skipped - BROM not in proper state (0x%x)\n",
···
 	dev_dbg(dev, "BCM-VK:%u created\n", id);
 
 	return 0;
+
+err_bcm_vk_tty_exit:
+	bcm_vk_tty_exit(vk);
 
 err_unregister_panic_notifier:
 	atomic_notifier_chain_unregister(&panic_notifier_list,
···
 	atomic_notifier_chain_unregister(&panic_notifier_list,
 					 &vk->panic_nb);
 
+	bcm_vk_msg_remove(vk);
+	bcm_vk_tty_exit(vk);
+
 	if (vk->tdma_vaddr)
 		dma_free_coherent(&pdev->dev, nr_scratch_pages * PAGE_SIZE,
 				  vk->tdma_vaddr, vk->tdma_addr);
···
 
 	cancel_work_sync(&vk->wq_work);
 	destroy_workqueue(vk->wq_thread);
+	cancel_work_sync(&vk->tty_wq_work);
+	destroy_workqueue(vk->tty_wq_thread);
 
 	for (i = 0; i < MAX_BAR; i++) {
 		if (vk->bar[i])

drivers/misc/bcm-vk/bcm_vk_tty.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018-2020 Broadcom.
+ */
+
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+
+#include "bcm_vk.h"
+
+/* TTYVK base offset is 0x30000 into BAR1 */
+#define BAR1_TTYVK_BASE_OFFSET	0x300000
+/* Each TTYVK channel (TO or FROM) is 0x10000 */
+#define BAR1_TTYVK_CHAN_OFFSET	0x100000
+/* Each TTYVK channel has TO and FROM, hence the * 2 */
+#define BAR1_TTYVK_BASE(index)	(BAR1_TTYVK_BASE_OFFSET + \
+				 ((index) * BAR1_TTYVK_CHAN_OFFSET * 2))
+/* TO TTYVK channel base comes before FROM for each index */
+#define TO_TTYK_BASE(index)	BAR1_TTYVK_BASE(index)
+#define FROM_TTYK_BASE(index)	(BAR1_TTYVK_BASE(index) + \
+				 BAR1_TTYVK_CHAN_OFFSET)
+
+struct bcm_vk_tty_chan {
+	u32 reserved;
+	u32 size;
+	u32 wr;
+	u32 rd;
+	u32 *data;
+};
+
+#define VK_BAR_CHAN(v, DIR, e)	((v)->DIR##_offset \
+				 + offsetof(struct bcm_vk_tty_chan, e))
+#define VK_BAR_CHAN_SIZE(v, DIR)	VK_BAR_CHAN(v, DIR, size)
+#define VK_BAR_CHAN_WR(v, DIR)		VK_BAR_CHAN(v, DIR, wr)
+#define VK_BAR_CHAN_RD(v, DIR)		VK_BAR_CHAN(v, DIR, rd)
+#define VK_BAR_CHAN_DATA(v, DIR, off)	(VK_BAR_CHAN(v, DIR, data) + (off))
+
+#define VK_BAR0_REGSEG_TTY_DB_OFFSET	0x86c
+
+/* Poll every 1/10 of second - temp hack till we use MSI interrupt */
+#define SERIAL_TIMER_VALUE (HZ / 10)
+
+static void bcm_vk_tty_poll(struct timer_list *t)
+{
+	struct bcm_vk *vk = from_timer(vk, t, serial_timer);
+
+	queue_work(vk->tty_wq_thread, &vk->tty_wq_work);
+	mod_timer(&vk->serial_timer, jiffies + SERIAL_TIMER_VALUE);
+}
+
+irqreturn_t bcm_vk_tty_irqhandler(int irq, void *dev_id)
+{
+	struct bcm_vk *vk = dev_id;
+
+	queue_work(vk->tty_wq_thread, &vk->tty_wq_work);
+
+	return IRQ_HANDLED;
+}
+
+static void bcm_vk_tty_wq_handler(struct work_struct *work)
+{
+	struct bcm_vk *vk = container_of(work, struct bcm_vk, tty_wq_work);
+	struct bcm_vk_tty *vktty;
+	int card_status;
+	int count;
+	unsigned char c;
+	int i;
+	int wr;
+
+	card_status = vkread32(vk, BAR_0, BAR_CARD_STATUS);
+	if (BCM_VK_INTF_IS_DOWN(card_status))
+		return;
+
+	for (i = 0; i < BCM_VK_NUM_TTY; i++) {
+		count = 0;
+		/* Check the card status that the tty channel is ready */
+		if ((card_status & BIT(i)) == 0)
+			continue;
+
+		vktty = &vk->tty[i];
+
+		/* Don't increment read index if tty app is closed */
+		if (!vktty->is_opened)
+			continue;
+
+		/* Fetch the wr offset in buffer from VK */
+		wr = vkread32(vk, BAR_1, VK_BAR_CHAN_WR(vktty, from));
+
+		/* safe to ignore until bar read gives proper size */
+		if (vktty->from_size == 0)
+			continue;
+
+		if (wr >= vktty->from_size) {
+			dev_err(&vk->pdev->dev,
+				"ERROR: wq handler ttyVK%d wr:0x%x > 0x%x\n",
+				i, wr, vktty->from_size);
+			/* Need to signal and close device in this case */
+			continue;
+		}
+
+		/*
+		 * Simple read of circular buffer and
+		 * insert into tty flip buffer
+		 */
+		while (vk->tty[i].rd != wr) {
+			c = vkread8(vk, BAR_1,
+				    VK_BAR_CHAN_DATA(vktty, from, vktty->rd));
+			vktty->rd++;
+			if (vktty->rd >= vktty->from_size)
+				vktty->rd = 0;
+			tty_insert_flip_char(&vktty->port, c, TTY_NORMAL);
+			count++;
+		}
+
+		if (count) {
+			tty_flip_buffer_push(&vktty->port);
+
+			/* Update read offset from shadow register to card */
+			vkwrite32(vk, vktty->rd, BAR_1,
+				  VK_BAR_CHAN_RD(vktty, from));
+		}
+	}
+}
+
+static int bcm_vk_tty_open(struct tty_struct *tty, struct file *file)
+{
+	int card_status;
+	struct bcm_vk *vk;
+	struct bcm_vk_tty *vktty;
+	int index;
+
+	/* initialize the pointer in case something fails */
+	tty->driver_data = NULL;
+
+	vk = (struct bcm_vk *)dev_get_drvdata(tty->dev);
+	index = tty->index;
+
+	if (index >= BCM_VK_NUM_TTY)
+		return -EINVAL;
+
+	vktty = &vk->tty[index];
+
+	vktty->pid = task_pid_nr(current);
+	vktty->to_offset = TO_TTYK_BASE(index);
+	vktty->from_offset = FROM_TTYK_BASE(index);
+
+	/* Do not allow tty device to be opened if tty on card not ready */
+	card_status = vkread32(vk, BAR_0, BAR_CARD_STATUS);
+	if (BCM_VK_INTF_IS_DOWN(card_status) || ((card_status & BIT(index)) == 0))
+		return -EBUSY;
+
+	/*
+	 * Get shadow registers of the buffer sizes and the "to" write offset
+	 * and "from" read offset
+	 */
+	vktty->to_size = vkread32(vk, BAR_1, VK_BAR_CHAN_SIZE(vktty, to));
+	vktty->wr = vkread32(vk, BAR_1,  VK_BAR_CHAN_WR(vktty, to));
+	vktty->from_size = vkread32(vk, BAR_1, VK_BAR_CHAN_SIZE(vktty, from));
+	vktty->rd = vkread32(vk, BAR_1,  VK_BAR_CHAN_RD(vktty, from));
+	vktty->is_opened = true;
+
+	if (tty->count == 1 && !vktty->irq_enabled) {
+		timer_setup(&vk->serial_timer, bcm_vk_tty_poll, 0);
+		mod_timer(&vk->serial_timer, jiffies + SERIAL_TIMER_VALUE);
+	}
+	return 0;
+}
+
+static void bcm_vk_tty_close(struct tty_struct *tty, struct file *file)
+{
+	struct bcm_vk *vk = dev_get_drvdata(tty->dev);
+
+	if (tty->index >= BCM_VK_NUM_TTY)
+		return;
+
+	vk->tty[tty->index].is_opened = false;
+
+	if (tty->count == 1)
+		del_timer_sync(&vk->serial_timer);
+}
+
+static void bcm_vk_tty_doorbell(struct bcm_vk *vk, u32 db_val)
+{
+	vkwrite32(vk, db_val, BAR_0,
+		  VK_BAR0_REGSEG_DB_BASE + VK_BAR0_REGSEG_TTY_DB_OFFSET);
+}
+
+static int bcm_vk_tty_write(struct tty_struct *tty,
+			    const unsigned char *buffer,
+			    int count)
+{
+	int index;
+	struct bcm_vk *vk;
+	struct bcm_vk_tty *vktty;
+	int i;
+
+	index = tty->index;
+	vk = dev_get_drvdata(tty->dev);
+	vktty = &vk->tty[index];
+
+	/* Simple write each byte to circular buffer */
+	for (i = 0; i < count; i++) {
+		vkwrite8(vk, buffer[i], BAR_1,
+			 VK_BAR_CHAN_DATA(vktty, to, vktty->wr));
+		vktty->wr++;
+		if (vktty->wr >= vktty->to_size)
+			vktty->wr = 0;
+	}
+	/* Update write offset from shadow register to card */
+	vkwrite32(vk, vktty->wr, BAR_1, VK_BAR_CHAN_WR(vktty, to));
+	bcm_vk_tty_doorbell(vk, 0);
+
+	return count;
+}
+
+static int bcm_vk_tty_write_room(struct tty_struct *tty)
+{
+	struct bcm_vk *vk = dev_get_drvdata(tty->dev);
+
+	return vk->tty[tty->index].to_size - 1;
+}
+
+static const struct tty_operations serial_ops = {
+	.open = bcm_vk_tty_open,
+	.close = bcm_vk_tty_close,
+	.write = bcm_vk_tty_write,
+	.write_room = bcm_vk_tty_write_room,
+};
+
+int bcm_vk_tty_init(struct bcm_vk *vk, char *name)
+{
+	int i;
+	int err;
+	struct tty_driver *tty_drv;
+	struct device *dev = &vk->pdev->dev;
+
+	tty_drv = tty_alloc_driver
+				(BCM_VK_NUM_TTY,
+				 TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV);
+	if (IS_ERR(tty_drv))
+		return PTR_ERR(tty_drv);
+
+	/* Save struct tty_driver for uninstalling the device */
+	vk->tty_drv = tty_drv;
+
+	/* initialize the tty driver */
+	tty_drv->driver_name = KBUILD_MODNAME;
+	tty_drv->name = kstrdup(name, GFP_KERNEL);
+	if (!tty_drv->name) {
+		err = -ENOMEM;
+		goto err_put_tty_driver;
+	}
+	tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
+	tty_drv->subtype = SERIAL_TYPE_NORMAL;
+	tty_drv->init_termios = tty_std_termios;
+	tty_set_operations(tty_drv, &serial_ops);
+
+	/* register the tty driver */
+	err = tty_register_driver(tty_drv);
+	if (err) {
+		dev_err(dev, "tty_register_driver failed\n");
+		goto err_kfree_tty_name;
+	}
+
+	for (i = 0; i < BCM_VK_NUM_TTY; i++) {
+		struct device *tty_dev;
+
+		tty_port_init(&vk->tty[i].port);
+		tty_dev = tty_port_register_device(&vk->tty[i].port, tty_drv,
+						   i, dev);
+		if (IS_ERR(tty_dev)) {
+			err = PTR_ERR(tty_dev);
+			goto unwind;
+		}
+		dev_set_drvdata(tty_dev, vk);
+		vk->tty[i].is_opened = false;
+	}
+
+	INIT_WORK(&vk->tty_wq_work, bcm_vk_tty_wq_handler);
+	vk->tty_wq_thread = create_singlethread_workqueue("tty");
+	if (!vk->tty_wq_thread) {
+		dev_err(dev, "Fail to create tty workqueue thread\n");
+		err = -ENOMEM;
+		goto unwind;
+	}
+	return 0;
+
+unwind:
+	while (--i >= 0)
+		tty_port_unregister_device(&vk->tty[i].port, tty_drv, i);
+	tty_unregister_driver(tty_drv);
+
+err_kfree_tty_name:
+	kfree(tty_drv->name);
+	tty_drv->name = NULL;
+
+err_put_tty_driver:
+	put_tty_driver(tty_drv);
+
+	return err;
+}
+
+void bcm_vk_tty_exit(struct bcm_vk *vk)
+{
+	int i;
+
+	del_timer_sync(&vk->serial_timer);
+	for (i = 0; i < BCM_VK_NUM_TTY; ++i) {
+		tty_port_unregister_device(&vk->tty[i].port,
+					   vk->tty_drv,
+					   i);
+		tty_port_destroy(&vk->tty[i].port);
+	}
+	tty_unregister_driver(vk->tty_drv);
+
+	kfree(vk->tty_drv->name);
+	vk->tty_drv->name = NULL;
+
+	put_tty_driver(vk->tty_drv);
+}
+
+void bcm_vk_tty_terminate_tty_user(struct bcm_vk *vk)
+{
+	struct bcm_vk_tty *vktty;
+	int i;
+
+	for (i = 0; i < BCM_VK_NUM_TTY; ++i) {
+		vktty = &vk->tty[i];
+		if (vktty->pid)
+			kill_pid(find_vpid(vktty->pid), SIGKILL, 1);
+	}
+}