atmel_serial.c

// SPDX-License-Identifier: GPL-2.0+
/*
 *  Driver for Atmel AT91 Serial ports
 *  Copyright (C) 2003 Rick Bronson
 *
 *  Based on drivers/char/serial_sa1100.c, by Deep Blue Solutions Ltd.
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  DMA support added by Chip Coldwell.
 */
#include <linux/tty.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/serial.h>
#include <linux/clk.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/tty_flip.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/atmel_pdc.h>
#include <linux/uaccess.h>
#include <linux/platform_data/atmel.h>
#include <linux/timer.h>
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <linux/err.h>
#include <linux/irq.h>
#include <linux/suspend.h>
#include <linux/mm.h>

#include <asm/div64.h>
#include <asm/io.h>
#include <asm/ioctls.h>

#define PDC_BUFFER_SIZE		512
/* Revisit: We should calculate this based on the actual port settings */
#define PDC_RX_TIMEOUT		(3 * 10)		/* 3 bytes */

/* The minium number of data FIFOs should be able to contain */
#define ATMEL_MIN_FIFO_SIZE	8
/*
 * These two offsets are substracted from the RX FIFO size to define the RTS
 * high and low thresholds
 */
#define ATMEL_RTS_HIGH_OFFSET	16
#define ATMEL_RTS_LOW_OFFSET	20

#if defined(CONFIG_SERIAL_ATMEL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/serial_core.h>

#include "serial_mctrl_gpio.h"
#include "atmel_serial.h"

static void atmel_start_rx(struct uart_port *port);
static void atmel_stop_rx(struct uart_port *port);

#ifdef CONFIG_SERIAL_ATMEL_TTYAT

/* Use device name ttyAT, major 204 and minor 154-169.  This is necessary if we
 * should coexist with the 8250 driver, such as if we have an external 16C550
 * UART. */
#define SERIAL_ATMEL_MAJOR	204
#define MINOR_START		154
#define ATMEL_DEVICENAME	"ttyAT"

#else

/* Use device name ttyS, major 4, minor 64-68.  This is the usual serial port
 * name, but it is legally reserved for the 8250 driver. */
#define SERIAL_ATMEL_MAJOR	TTY_MAJOR
#define MINOR_START		64
#define ATMEL_DEVICENAME	"ttyS"

#endif

#define ATMEL_ISR_PASS_LIMIT	256

struct atmel_dma_buffer {
	unsigned char	*buf;
	dma_addr_t	dma_addr;
	unsigned int	dma_size;
	unsigned int	ofs;
};

struct atmel_uart_char {
	u16		status;
	u16		ch;
};

/*
 * Be careful, the real size of the ring buffer is
 * sizeof(atmel_uart_char) * ATMEL_SERIAL_RINGSIZE. It means that ring buffer
 * can contain up to 1024 characters in PIO mode and up to 4096 characters in
 * DMA mode.
 */
#define ATMEL_SERIAL_RINGSIZE 1024

/*
 * at91: 6 USARTs and one DBGU port (SAM9260)
 * samx7: 3 USARTs and 5 UARTs
 */
#define ATMEL_MAX_UART		8

/*
 * We wrap our port structure around the generic uart_port.
 */
struct atmel_uart_port {
	struct uart_port	uart;		/* uart */
	struct clk		*clk;		/* uart clock */
	int			may_wakeup;	/* cached value of device_may_wakeup for times we need to disable it */
	u32			backup_imr;	/* IMR saved during suspend */
	int			break_active;	/* break being received */

	bool			use_dma_rx;	/* enable DMA receiver */
	bool			use_pdc_rx;	/* enable PDC receiver */
	short			pdc_rx_idx;	/* current PDC RX buffer */
	struct atmel_dma_buffer	pdc_rx[2];	/* PDC receier */

	bool			use_dma_tx;     /* enable DMA transmitter */
	bool			use_pdc_tx;	/* enable PDC transmitter */
	struct atmel_dma_buffer	pdc_tx;		/* PDC transmitter */

	spinlock_t			lock_tx;	/* port lock */
	spinlock_t			lock_rx;	/* port lock */
	struct dma_chan			*chan_tx;
	struct dma_chan			*chan_rx;
	struct dma_async_tx_descriptor	*desc_tx;
	struct dma_async_tx_descriptor	*desc_rx;
	dma_cookie_t			cookie_tx;
	dma_cookie_t			cookie_rx;
	struct scatterlist		sg_tx;
	struct scatterlist		sg_rx;
	struct tasklet_struct	tasklet_rx;
	struct tasklet_struct	tasklet_tx;
	atomic_t		tasklet_shutdown;
	unsigned int		irq_status_prev;
	unsigned int		tx_len;

	struct circ_buf		rx_ring;

	struct mctrl_gpios	*gpios;
	u32			backup_mode;	/* MR saved during iso7816 operations */
	u32			backup_brgr;	/* BRGR saved during iso7816 operations */
	unsigned int		tx_done_mask;
	u32			fifo_size;
	u32			rts_high;
	u32			rts_low;
	bool			ms_irq_enabled;
	u32			rtor;	/* address of receiver timeout register if it exists */
	bool			has_frac_baudrate;
	bool			has_hw_timer;
	struct timer_list	uart_timer;

	bool			tx_stopped;
	bool			suspended;
	unsigned int		pending;
	unsigned int		pending_status;
	spinlock_t		lock_suspended;

	bool			hd_start_rx;	/* can start RX during half-duplex operation */

	/* ISO7816 */
	unsigned int		fidi_min;
	unsigned int		fidi_max;

#ifdef CONFIG_PM
	struct {
		u32		cr;
		u32		mr;
		u32		imr;
		u32		brgr;
		u32		rtor;
		u32		ttgr;
		u32		fmr;
		u32		fimr;
	} cache;
#endif

	int (*prepare_rx)(struct uart_port *port);
	int (*prepare_tx)(struct uart_port *port);
	void (*schedule_rx)(struct uart_port *port);
	void (*schedule_tx)(struct uart_port *port);
	void (*release_rx)(struct uart_port *port);
	void (*release_tx)(struct uart_port *port);
};

static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
static DECLARE_BITMAP(atmel_ports_in_use, ATMEL_MAX_UART);

#ifdef SUPPORT_SYSRQ
static struct console atmel_console;