Currently DMA mode is enforced if the certain driver has such support. It
prevents user to enforce PIO mode for RX, TX, or both.
The new module parameters skip_rxdma and skip_txdma allow user to choose
between auto mode, which is current and default behaviour, disable RX, TX, or
both DMA channels without hacking a kernel.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250.h | 2 ++
drivers/tty/serial/8250/8250_core.c | 28 ++++++++++++++++++++--------
drivers/tty/serial/8250/8250_dma.c | 12 +++++++++++-
drivers/tty/serial/8250/8250_port.c | 6 ++----
include/linux/serial_core.h | 2 ++
5 files changed, 37 insertions(+), 13 deletions(-)
diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index a697a85..9ffa8d1 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -50,6 +50,8 @@ struct uart_8250_dma {
unsigned char tx_running;
unsigned char tx_err;
unsigned char rx_running;
+
+ bool in_use;
};
struct old_serial_port {
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 5a75146..0c6ced9 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -58,6 +58,9 @@ static struct uart_driver serial8250_reg;
static unsigned int skip_txen_test; /* force skip of txen test at init time */
+static bool skip_rxdma; /* force skip using of Rx DMA */
+static bool skip_txdma; /* force skip using of Tx DMA */
+
#define PASS_LIMIT 512
#include <asm/serial.h>
@@ -497,6 +500,13 @@ static void univ8250_rsa_support(struct uart_ops *ops)
#define univ8250_rsa_support(x) do { } while (0)
#endif /* CONFIG_SERIAL_8250_RSA */
+static void serial8250_apply_quirks(struct uart_8250_port *up)
+{
+ up->port.quirks |= skip_txen_test ? UPQ_NO_TXEN_TEST : 0;
+ up->port.quirks |= skip_rxdma ? UPQ_NO_DMA_RX : 0;
+ up->port.quirks |= skip_txdma ? UPQ_NO_DMA_TX : 0;
+}
+
static void __init serial8250_isa_init_ports(void)
{
struct uart_8250_port *up;
@@ -577,9 +587,7 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev)
up->port.dev = dev;
- if (skip_txen_test)
- up->port.quirks |= UPQ_NO_TXEN_TEST;
-
+ serial8250_apply_quirks(up);
uart_add_one_port(drv, &up->port);
}
}
@@ -1005,9 +1013,6 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
if (up->port.dev)
uart->port.dev = up->port.dev;
- if (skip_txen_test)
- uart->port.quirks |= UPQ_NO_TXEN_TEST;
-
if (up->port.flags & UPF_FIXED_TYPE)
uart->port.type = up->port.type;
@@ -1040,6 +1045,8 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
if (up->dl_write)
uart->dl_write = up->dl_write;
+ serial8250_apply_quirks(uart);
+
if (uart->port.type != PORT_8250_CIR) {
if (serial8250_isa_config != NULL)
serial8250_isa_config(0, &uart->port,
@@ -1089,11 +1096,10 @@ void serial8250_unregister_port(int line)
uart_remove_one_port(&serial8250_reg, &uart->port);
if (serial8250_isa_devs) {
uart->port.flags &= ~UPF_BOOT_AUTOCONF;
- if (skip_txen_test)
- uart->port.quirks |= UPQ_NO_TXEN_TEST;
uart->port.type = PORT_UNKNOWN;
uart->port.dev = &serial8250_isa_devs->dev;
uart->capabilities = 0;
+ serial8250_apply_quirks(uart);
uart_add_one_port(&serial8250_reg, &uart->port);
} else {
uart->port.dev = NULL;
@@ -1197,6 +1203,12 @@ MODULE_PARM_DESC(nr_uarts, "Maximum number of UARTs supported. (1-" __MODULE_STR
module_param(skip_txen_test, uint, 0644);
MODULE_PARM_DESC(skip_txen_test, "Skip checking for the TXEN bug at init time");
+module_param(skip_rxdma, bool, 0644);
+MODULE_PARM_DESC(skip_rxdma, "Skip using of Rx DMA.");
+
+module_param(skip_txdma, bool, 0644);
+MODULE_PARM_DESC(skip_txdma, "Skip using of Tx DMA.");
+
#ifdef CONFIG_SERIAL_8250_RSA
module_param_array(probe_rsa, ulong, &probe_rsa_count, 0444);
MODULE_PARM_DESC(probe_rsa, "Probe I/O ports for RSA");
diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index fdbddbc..c864bce 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -72,6 +72,11 @@ int serial8250_tx_dma(struct uart_8250_port *p)
struct dma_async_tx_descriptor *desc;
int ret;
+ if (!dma->in_use || p->port.quirks & UPQ_NO_DMA_TX) {
+ ret = -ENODEV;
+ goto err;
+ }
+
if (uart_tx_stopped(&p->port) || dma->tx_running ||
uart_circ_empty(xmit))
return 0;
@@ -115,6 +120,9 @@ int serial8250_rx_dma(struct uart_8250_port *p)
struct uart_8250_dma *dma = p->dma;
struct dma_async_tx_descriptor *desc;
+ if (!dma->in_use || p->port.quirks & UPQ_NO_DMA_RX)
+ return -ENODEV;
+
if (dma->rx_running)
return 0;
@@ -232,6 +240,7 @@ int serial8250_request_dma(struct uart_8250_port *p)
goto err;
}
+ dma->in_use = true;
dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
return 0;
@@ -247,7 +256,7 @@ void serial8250_release_dma(struct uart_8250_port *p)
{
struct uart_8250_dma *dma = p->dma;
- if (!dma)
+ if (!dma->in_use)
return;
/* Release RX resources */
@@ -265,6 +274,7 @@ void serial8250_release_dma(struct uart_8250_port *p)
dma->txchan = NULL;
dma->tx_running = 0;
+ dma->in_use = false;
dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
}
EXPORT_SYMBOL_GPL(serial8250_release_dma);
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index cc03737..2cc4196 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2316,11 +2316,9 @@ int serial8250_do_startup(struct uart_port *port)
*/
if (up->dma) {
retval = serial8250_request_dma(up);
- if (retval) {
+ if (retval)
pr_warn_ratelimited("ttyS%d - failed to request DMA\n",
serial_index(port));
- up->dma = NULL;
- }
}
/*
@@ -2573,7 +2571,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
if (up->capabilities & UART_CAP_FIFO && port->fifosize > 1) {
/* NOTE: If fifo_bug is not set, a user can set RX_trigger. */
- if ((baud < 2400 && !up->dma) || up->fifo_bug) {
+ if ((baud < 2400 && (!up->dma || !up->dma->in_use)) || up->fifo_bug) {
up->fcr &= ~UART_FCR_TRIGGER_MASK;
up->fcr |= UART_FCR_TRIGGER_1;
}
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 509f6c5..c9da6e4 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -247,6 +247,8 @@ struct uart_port {
/* quirks must be updated while holding port mutex */
#define UPQ_NO_TXEN_TEST (1 << 0)
+#define UPQ_NO_DMA_RX (1 << 1)
+#define UPQ_NO_DMA_TX (1 << 2)
struct attribute_group *attr_group; /* port specific attributes */
const struct attribute_group **tty_groups; /* all attributes (serial core use only) */
--
2.9.3
--
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