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path: root/drivers/tty/serial/amba-pl011.c
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Diffstat (limited to 'drivers/tty/serial/amba-pl011.c')
-rw-r--r--drivers/tty/serial/amba-pl011.c234
1 files changed, 129 insertions, 105 deletions
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 8d94c194f090..5a4e9d579585 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -58,6 +58,7 @@
#include <linux/pinctrl/consumer.h>
#include <linux/sizes.h>
#include <linux/io.h>
+#include <linux/workqueue.h>
#define UART_NR 14
@@ -156,7 +157,9 @@ struct uart_amba_port {
unsigned int lcrh_tx; /* vendor-specific */
unsigned int lcrh_rx; /* vendor-specific */
unsigned int old_cr; /* state during shutdown */
+ struct delayed_work tx_softirq_work;
bool autorts;
+ unsigned int tx_irq_seen; /* 0=none, 1=1, 2=2 or more */
char type[12];
#ifdef CONFIG_DMA_ENGINE
/* DMA stuff */
@@ -164,6 +167,7 @@ struct uart_amba_port {
bool using_rx_dma;
struct pl011_dmarx_data dmarx;
struct pl011_dmatx_data dmatx;
+ bool dma_probed;
#endif
};
@@ -261,10 +265,11 @@ static void pl011_sgbuf_free(struct dma_chan *chan, struct pl011_sgbuf *sg,
}
}
-static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *uap)
+static void pl011_dma_probe(struct uart_amba_port *uap)
{
/* DMA is the sole user of the platform data right now */
struct amba_pl011_data *plat = dev_get_platdata(uap->port.dev);
+ struct device *dev = uap->port.dev;
struct dma_slave_config tx_conf = {
.dst_addr = uap->port.mapbase + UART01x_DR,
.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
@@ -275,9 +280,14 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *
struct dma_chan *chan;
dma_cap_mask_t mask;
- chan = dma_request_slave_channel(dev, "tx");
+ uap->dma_probed = true;
+ chan = dma_request_slave_channel_reason(dev, "tx");
+ if (IS_ERR(chan)) {
+ if (PTR_ERR(chan) == -EPROBE_DEFER) {
+ uap->dma_probed = false;
+ return;
+ }
- if (!chan) {
/* We need platform data */
if (!plat || !plat->dma_filter) {
dev_info(uap->port.dev, "no DMA platform data\n");
@@ -385,63 +395,17 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *
}
}
-#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;
- struct device *dev;
-};
-
-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->dev, dmau->uap);
- list_del(node);
- kfree(dmau);
- }
- return 0;
-}
-
-device_initcall(pl011_dma_initcall);
-
-static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap)
-{
- struct dma_uap *dmau = kzalloc(sizeof(struct dma_uap), GFP_KERNEL);
- if (dmau) {
- dmau->uap = uap;
- dmau->dev = dev;
- list_add_tail(&dmau->node, &pl011_dma_uarts);
- }
-}
-#else
-static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap)
-{
- pl011_dma_probe_initcall(dev, 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);
if (uap->dmarx.chan)
dma_release_channel(uap->dmarx.chan);
}
-/* Forward declare this for the refill routine */
+/* Forward declare these for the refill routine */
static int pl011_dma_tx_refill(struct uart_amba_port *uap);
+static void pl011_start_tx_pio(struct uart_amba_port *uap);
/*
* The current DMA TX buffer has been sent.
@@ -479,14 +443,13 @@ static void pl011_dma_tx_callback(void *data)
return;
}
- if (pl011_dma_tx_refill(uap) <= 0) {
+ 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 + UART011_IMSC);
- }
+ pl011_start_tx_pio(uap);
+
spin_unlock_irqrestore(&uap->port.lock, flags);
}
@@ -664,12 +627,10 @@ static inline bool pl011_dma_tx_start(struct uart_amba_port *uap)
if (!uap->dmatx.queued) {
if (pl011_dma_tx_refill(uap) > 0) {
uap->im &= ~UART011_TXIM;
- ret = true;
- } else {
- uap->im |= UART011_TXIM;
+ writew(uap->im, uap->port.membase +
+ UART011_IMSC);
+ } else
ret = false;
- }
- writew(uap->im, uap->port.membase + UART011_IMSC);
} else if (!(uap->dmacr & UART011_TXDMAE)) {
uap->dmacr |= UART011_TXDMAE;
writew(uap->dmacr,
@@ -1021,6 +982,9 @@ static void pl011_dma_startup(struct uart_amba_port *uap)
{
int ret;
+ if (!uap->dma_probed)
+ pl011_dma_probe(uap);
+
if (!uap->dmatx.chan)
return;
@@ -1142,7 +1106,7 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
#else
/* Blank functions if the DMA engine is not available */
-static inline void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap)
+static inline void pl011_dma_probe(struct uart_amba_port *uap)
{
}
@@ -1208,15 +1172,24 @@ static void pl011_stop_tx(struct uart_port *port)
pl011_dma_tx_stop(uap);
}
+static bool pl011_tx_chars(struct uart_amba_port *uap);
+
+/* Start TX with programmed I/O only (no DMA) */
+static void pl011_start_tx_pio(struct uart_amba_port *uap)
+{
+ uap->im |= UART011_TXIM;
+ writew(uap->im, uap->port.membase + UART011_IMSC);
+ if (!uap->tx_irq_seen)
+ pl011_tx_chars(uap);
+}
+
static void pl011_start_tx(struct uart_port *port)
{
struct uart_amba_port *uap =
container_of(port, struct uart_amba_port, port);
- if (!pl011_dma_tx_start(uap)) {
- uap->im |= UART011_TXIM;
- writew(uap->im, uap->port.membase + UART011_IMSC);
- }
+ if (!pl011_dma_tx_start(uap))
+ pl011_start_tx_pio(uap);
}
static void pl011_stop_rx(struct uart_port *port)
@@ -1274,40 +1247,87 @@ __acquires(&uap->port.lock)
spin_lock(&uap->port.lock);
}
-static void pl011_tx_chars(struct uart_amba_port *uap)
+/*
+ * Transmit a character
+ * There must be at least one free entry in the TX FIFO to accept the char.
+ *
+ * Returns true if the FIFO might have space in it afterwards;
+ * returns false if the FIFO definitely became full.
+ */
+static bool pl011_tx_char(struct uart_amba_port *uap, unsigned char c)
+{
+ writew(c, uap->port.membase + UART01x_DR);
+ uap->port.icount.tx++;
+
+ if (likely(uap->tx_irq_seen > 1))
+ return true;
+
+ return !(readw(uap->port.membase + UART01x_FR) & UART01x_FR_TXFF);
+}
+
+static bool pl011_tx_chars(struct uart_amba_port *uap)
{
struct circ_buf *xmit = &uap->port.state->xmit;
int count;
+ if (unlikely(uap->tx_irq_seen < 2))
+ /*
+ * Initial FIFO fill level unknown: we must check TXFF
+ * after each write, so just try to fill up the FIFO.
+ */
+ count = uap->fifosize;
+ else /* tx_irq_seen >= 2 */
+ /*
+ * FIFO initially at least half-empty, so we can simply
+ * write half the FIFO without polling TXFF.
+
+ * Note: the *first* TX IRQ can still race with
+ * pl011_start_tx_pio(), which can result in the FIFO
+ * being fuller than expected in that case.
+ */
+ count = uap->fifosize >> 1;
+
+ /*
+ * If the FIFO is full we're guaranteed a TX IRQ at some later point,
+ * and can't transmit immediately in any case:
+ */
+ if (unlikely(uap->tx_irq_seen < 2 &&
+ readw(uap->port.membase + UART01x_FR) & UART01x_FR_TXFF))
+ return false;
+
if (uap->port.x_char) {
- writew(uap->port.x_char, uap->port.membase + UART01x_DR);
- uap->port.icount.tx++;
+ pl011_tx_char(uap, uap->port.x_char);
uap->port.x_char = 0;
- return;
+ --count;
}
if (uart_circ_empty(xmit) || uart_tx_stopped(&uap->port)) {
pl011_stop_tx(&uap->port);
- return;
+ goto done;
}
/* If we are using DMA mode, try to send some characters. */
if (pl011_dma_tx_irq(uap))
- return;
+ goto done;
- count = uap->fifosize >> 1;
- do {
- writew(xmit->buf[xmit->tail], uap->port.membase + UART01x_DR);
+ while (count-- > 0 && pl011_tx_char(uap, xmit->buf[xmit->tail])) {
xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
- uap->port.icount.tx++;
if (uart_circ_empty(xmit))
break;
- } while (--count > 0);
+ }
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(&uap->port);
- if (uart_circ_empty(xmit))
+ if (uart_circ_empty(xmit)) {
pl011_stop_tx(&uap->port);
+ goto done;
+ }
+
+ if (unlikely(!uap->tx_irq_seen))
+ schedule_delayed_work(&uap->tx_softirq_work, uap->port.timeout);
+
+done:
+ return false;
}
static void pl011_modem_status(struct uart_amba_port *uap)
@@ -1334,6 +1354,28 @@ static void pl011_modem_status(struct uart_amba_port *uap)
wake_up_interruptible(&uap->port.state->port.delta_msr_wait);
}
+static void pl011_tx_softirq(struct work_struct *work)
+{
+ struct delayed_work *dwork = to_delayed_work(work);
+ struct uart_amba_port *uap =
+ container_of(dwork, struct uart_amba_port, tx_softirq_work);
+
+ spin_lock(&uap->port.lock);
+ while (pl011_tx_chars(uap)) ;
+ spin_unlock(&uap->port.lock);
+}
+
+static void pl011_tx_irq_seen(struct uart_amba_port *uap)
+{
+ if (likely(uap->tx_irq_seen > 1))
+ return;
+
+ uap->tx_irq_seen++;
+ if (uap->tx_irq_seen < 2)
+ /* first TX IRQ */
+ cancel_delayed_work(&uap->tx_softirq_work);
+}
+
static irqreturn_t pl011_int(int irq, void *dev_id)
{
struct uart_amba_port *uap = dev_id;
@@ -1372,8 +1414,10 @@ static irqreturn_t pl011_int(int irq, void *dev_id)
if (status & (UART011_DSRMIS|UART011_DCDMIS|
UART011_CTSMIS|UART011_RIMIS))
pl011_modem_status(uap);
- if (status & UART011_TXIS)
+ if (status & UART011_TXIS) {
+ pl011_tx_irq_seen(uap);
pl011_tx_chars(uap);
+ }
if (pass_counter-- == 0)
break;
@@ -1577,7 +1621,7 @@ static int pl011_startup(struct uart_port *port)
{
struct uart_amba_port *uap =
container_of(port, struct uart_amba_port, port);
- unsigned int cr, lcr_h, fbrd, ibrd;
+ unsigned int cr;
int retval;
retval = pl011_hwinit(port);
@@ -1595,30 +1639,8 @@ static int pl011_startup(struct uart_port *port)
writew(uap->vendor->ifls, uap->port.membase + UART011_IFLS);
- /*
- * Provoke TX FIFO interrupt into asserting. Taking care to preserve
- * baud rate and data format specified by FBRD, IBRD and LCRH as the
- * UART may already be in use as a console.
- */
spin_lock_irq(&uap->port.lock);
- fbrd = readw(uap->port.membase + UART011_FBRD);
- ibrd = readw(uap->port.membase + UART011_IBRD);
- lcr_h = readw(uap->port.membase + uap->lcrh_rx);
-
- cr = UART01x_CR_UARTEN | UART011_CR_TXE | UART011_CR_LBE;
- writew(cr, uap->port.membase + UART011_CR);
- writew(0, uap->port.membase + UART011_FBRD);
- writew(1, uap->port.membase + UART011_IBRD);
- pl011_write_lcr_h(uap, 0);
- writew(0, uap->port.membase + UART01x_DR);
- while (readw(uap->port.membase + UART01x_FR) & UART01x_FR_BUSY)
- barrier();
-
- writew(fbrd, uap->port.membase + UART011_FBRD);
- writew(ibrd, uap->port.membase + UART011_IBRD);
- pl011_write_lcr_h(uap, lcr_h);
-
/* restore RTS and DTR */
cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR);
cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE;
@@ -1672,13 +1694,15 @@ static void pl011_shutdown(struct uart_port *port)
container_of(port, struct uart_amba_port, port);
unsigned int cr;
+ cancel_delayed_work_sync(&uap->tx_softirq_work);
+
/*
* disable all interrupts
*/
spin_lock_irq(&uap->port.lock);
uap->im = 0;
writew(uap->im, uap->port.membase + UART011_IMSC);
- writew(0xffff, uap->port.membase + UART011_ICR);
+ writew(0xffff & ~UART011_TXIS, uap->port.membase + UART011_ICR);
spin_unlock_irq(&uap->port.lock);
pl011_dma_shutdown(uap);
@@ -2218,7 +2242,7 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
uap->port.ops = &amba_pl011_pops;
uap->port.flags = UPF_BOOT_AUTOCONF;
uap->port.line = i;
- pl011_dma_probe(&dev->dev, uap);
+ INIT_DELAYED_WORK(&uap->tx_softirq_work, pl011_tx_softirq);
/* Ensure interrupts from this UART are masked and cleared */
writew(0, uap->port.membase + UART011_IMSC);
@@ -2233,7 +2257,8 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
if (!amba_reg.state) {
ret = uart_register_driver(&amba_reg);
if (ret < 0) {
- pr_err("Failed to register AMBA-PL011 driver\n");
+ dev_err(&dev->dev,
+ "Failed to register AMBA-PL011 driver\n");
return ret;
}
}
@@ -2242,7 +2267,6 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
if (ret) {
amba_ports[i] = NULL;
uart_unregister_driver(&amba_reg);
- pl011_dma_remove(uap);
}
return ret;