path: root/drivers/tty/serial/amba-pl011.c

/*
 *  linux/drivers/char/amba.c
 *
 *  Driver for AMBA serial ports
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  Copyright 1999 ARM Limited
 *  Copyright (C) 2000 Deep Blue Solutions Ltd.
 *  Copyright (C) 2010 ST-Ericsson SA
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * This is a generic driver for ARM AMBA-type serial ports.  They
 * have a lot of 16550-like features, but are not register compatible.
 * Note that although they do have CTS, DCD and DSR inputs, they do
 * not have an RI input, nor do they have DTR or RTS outputs.  If
 * required, these have to be supplied via some other means (eg, GPIO)
 * and hooked into this driver.
 */

#if defined(CONFIG_SERIAL_AMBA_PL011_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/amba/bus.h>
#include <linux/amba/serial.h>
#include <linux/clk.h>
#include <linux/slab.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>

#include <asm/io.h>
#include <asm/sizes.h>

#define UART_NR			14

#define SERIAL_AMBA_MAJOR	204
#define SERIAL_AMBA_MINOR	64
#define SERIAL_AMBA_NR		UART_NR

#define AMBA_ISR_PASS_LIMIT	256

#define UART_DR_ERROR		(UART011_DR_OE|UART011_DR_BE|UART011_DR_PE|UART011_DR_FE)
#define UART_DUMMY_DR_RX	(1 << 16)

/* There is by now at least one vendor with differing details, so handle it */
struct vendor_data {
	unsigned int		ifls;
	unsigned int		fifosize;
	unsigned int		lcrh_tx;
	unsigned int		lcrh_rx;
	bool			oversampling;
	bool			dma_threshold;
};

static struct vendor_data vendor_arm = {
	.ifls			= UART011_IFLS_RX4_8|UART011_IFLS_TX4_8,
	.fifosize		= 16,
	.lcrh_tx		= UART011_LCRH,
	.lcrh_rx		= UART011_LCRH,
	.oversampling		= false,
	.dma_threshold		= false,
};

static struct vendor_data vendor_st = {
	.ifls			= UART011_IFLS_RX_HALF|UART011_IFLS_TX_HALF,
	.fifosize		= 64,
	.lcrh_tx		= ST_UART011_LCRH_TX,
	.lcrh_rx		= ST_UART011_LCRH_RX,
	.oversampling		= true,
	.dma_threshold		= true,
};

/* Deals with DMA transactions */
struct pl011_dmatx_data {
	struct dma_chan		*chan;
	struct scatterlist	sg;
	char			*buf;
	bool			queued;
};

/*
 * We wrap our port structure around the generic uart_port.
 */
struct uart_amba_port {
	struct uart_port	port;
	struct clk		*clk;
	const struct vendor_data *vendor;
	unsigned int		dmacr;		/* dma control reg */
	unsigned int		im;		/* interrupt mask */
	unsigned int		old_status;
	unsigned int		fifosize;	/* vendor-specific */
	unsigned int		lcrh_tx;	/* vendor-specific */
	unsigned int		lcrh_rx;	/* vendor-specific */
	bool			autorts;
	char			type[12];
#ifdef CONFIG_DMA_ENGINE
	/* DMA stuff */
	bool			using_dma;
	struct pl011_dmatx_data	dmatx;
#endif
};

/*
 * All the DMA operation mode stuff goes inside this ifdef.
 * This assumes that you have a generic DMA device interface,
 * no custom DMA interfaces are supported.
 */
#ifdef CONFIG_DMA_ENGINE

#define PL011_DMA_BUFFER_SIZE PAGE_SIZE

static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
{
	/* DMA is the sole user of the platform data right now */
	struct amba_pl011_data *plat = uap->port.dev->platform_data;
	struct dma_slave_config tx_conf = {
		.dst_addr = uap->port.mapbase + UART01x_DR,
		.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
		.direction = DMA_TO_DEVICE,
		.dst_maxburst = uap->fifosize >> 1,
	};
	struct dma_chan *chan;
	dma_cap_mask_t mask;

	/* We need platform data */
	if (!plat || !plat->dma_filter) {
		dev_info(uap->port.dev, "no DMA platform data\n");
		return;
	}

	/* Try to acquire a generic DMA engine slave channel */
	dma_cap_zero(mask);
	dma_cap_set(DMA_SLAVE, mask);

	chan = dma_request_channel(mask, plat->dma_filter, plat->dma_tx_param);
	if (!chan) {
		dev_err(uap->port.dev, "no TX DMA channel!\n");
		return;
	}

	dmaengine_slave_config(chan, &tx_conf);
	uap->dmatx.chan = chan;

	dev_info(uap->port.dev, "DMA channel TX %s\n",
		 dma_chan_name(uap->dmatx.chan));
}

#ifndef MODULE
/*
 * Stack up the UARTs and let the above initcall be done at device
 * initcall time, because the serial driver is called as an arch
 * initcall, and at this time the DMA subsystem is not yet registered.
 * At this point the driver will switch over to using DMA where desired.
 */
struct dma_uap {
	struct list_head node;
	struct uart_amba_port *uap;
};

static LIST_HEAD(pl011_dma_uarts);

static int __init pl011_dma_initcall(void)
{
	struct list_head *node, *tmp;

	list_for_each_safe(node, tmp, &pl011_dma_uarts) {
		struct dma_uap *dmau = list_entry(node, struct dma_uap, node);
		pl011_dma_probe_initcall(dmau->uap);
		list_del(node);
		kfree(dmau);
	}
	return 0;
}

device_initcall(pl011_dma_initcall);

static void pl011_dma_probe(struct uart_amba_port *uap)
{
	struct dma_uap *dmau = kzalloc(sizeof(struct dma_uap), GFP_KERNEL);
	if (dmau) {
		dmau->uap = uap;
		list_add_tail(&dmau->node, &pl011_dma_uarts);
	}
}
#else
static void pl011_dma_probe(struct uart_amba_port *uap)
{
	pl011_dma_probe_initcall(uap);
}
#endif

static void pl011_dma_remove(struct uart_amba_port *uap)
{
	/* TODO: remove the initcall if it has not yet executed */
	if (uap->dmatx.chan)
		dma_release_channel(uap->dmatx.chan);
}


/* Forward declare this for the refill routine */
static int pl011_dma_tx_refill(struct uart_amba_port *uap);

/*
 * The current DMA TX buffer has been sent.
 * Try to queue up another DMA buffer.
 */
static void pl011_dma_tx_callback(void *data)
{
	struct uart_amba_port *uap = data;
	struct pl011_dmatx_data *dmatx = &uap->dmatx;
	unsigned long flags;
	u16 dmacr;

	spin_lock_irqsave(&uap->port.lock, flags);
	if (uap->dmatx.queued)
		dma_unmap_sg(dmatx->chan->device->dev, &dmatx->sg, 1,
			     DMA_TO_DEVICE);

	dmacr = uap->dmacr;
	uap->dmacr = dmacr & ~UART011_TXDMAE;
	writew(uap->dmacr, uap->port.membase + UART011_DMACR);

	/*
	 * If TX DMA was disabled, it means that we've stopped the DMA for
	 * some reason (eg, XOFF received, or we want to send an X-char.)
	 *
	 * Note: we need to be careful here of a potential race between DMA
	 * and the rest of the driver - if the driver disables TX DMA while
	 * a TX buffer completing, we must update the tx queued status to
	 * get further refills (hence we check dmacr).
	 */
	if (!(dmacr & UART011_TXDMAE) || uart_tx_stopped(&uap->port) ||
	    uart_circ_empty(&uap->port.state->xmit)) {
		uap->dmatx.queued = false;
		spin_unlock_irqrestore(&uap->port.lock, flags);
		return;
	}

	if (pl011_dma_tx_refill(uap) <= 0) {
		/*
		 * We didn't queue a DMA buffer for some reason, but we
		 * have data pending to be sent.  Re-enable the TX IRQ.
		 */
		uap->im |= UART011_TXIM;
		writew(uap->im, uap->port.membase + UART0