From: "Matwey V. Kornilov" <matwey@sai.msu.ru> Implementation of software emulation of RS485 direction handling is based on omap_serial driver. Before and after transmission RTS is set to the appropriate value. Note that before calling serial8250_em485_init() the caller has to ensure that UART will interrupt when shift register empty. Otherwise, emultaion cannot be used. Both serial8250_em485_init() and serial8250_em485_destroy() are idempotent functions. Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Patch-mainline: Queued in linux-next for 4.6-rc1 Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git Git-commit: e490c9144cfaa8e2242c1e5d5187230928f27417 Signed-off-by: Matwey V. Kornilov <matwey.kornilov@gmail.com> --- drivers/tty/serial/8250/8250.h | 2 + drivers/tty/serial/8250/8250_port.c | 223 +++++++++++++++++++++++++++++++++++- include/linux/serial_8250.h | 8 ++ 3 files changed, 229 insertions(+), 4 deletions(-) diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h index d54dcd8..ce587c0 100644 --- a/drivers/tty/serial/8250/8250.h +++ b/drivers/tty/serial/8250/8250.h @@ -117,6 +117,8 @@ static inline void serial_dl_write(struct uart_8250_port *up, int value) struct uart_8250_port *serial8250_get_port(int line); void serial8250_rpm_get(struct uart_8250_port *p); void serial8250_rpm_put(struct uart_8250_port *p); +int serial8250_em485_init(struct uart_8250_port *p); +void serial8250_em485_destroy(struct uart_8250_port *p); #if defined(__alpha__) && !defined(CONFIG_PCI) /* diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 04681e5..01a85a7 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -37,6 +37,7 @@ #include <linux/slab.h> #include <linux/uaccess.h> #include <linux/pm_runtime.h> +#include <linux/timer.h> #include <asm/io.h> #include <asm/irq.h> @@ -522,6 +523,20 @@ static void serial8250_clear_fifos(struct uart_8250_port *p) } } +static inline void serial8250_em485_rts_after_send(struct uart_8250_port *p) +{ + unsigned char mcr = serial_in(p, UART_MCR); + + if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) + mcr |= UART_MCR_RTS; + else + mcr &= ~UART_MCR_RTS; + serial_out(p, UART_MCR, mcr); +} + +static void serial8250_em485_handle_start_tx(unsigned long arg); +static void serial8250_em485_handle_stop_tx(unsigned long arg); + void serial8250_clear_and_reinit_fifos(struct uart_8250_port *p) { serial8250_clear_fifos(p); @@ -546,6 +561,73 @@ void serial8250_rpm_put(struct uart_8250_port *p) } EXPORT_SYMBOL_GPL(serial8250_rpm_put); +/** + * serial8250_em485_init() - put uart_8250_port into rs485 emulating + * @p: uart_8250_port port instance + * + * The function is used to start rs485 software emulating on the + * &struct uart_8250_port* @p. Namely, RTS is switched before/after + * transmission. The function is idempotent, so it is safe to call it + * multiple times. + * + * The caller MUST enable interrupt on empty shift register before + * calling serial8250_em485_init(). This interrupt is not a part of + * 8250 standard, but implementation defined. + * + * The function is supposed to be called from .rs485_config callback + * or from any other callback protected with p->port.lock spinlock. + * + * See also serial8250_em485_destroy() + * + * Return 0 - success, -errno - otherwise + */ +int serial8250_em485_init(struct uart_8250_port *p) +{ + if (p->em485 != NULL) + return 0; + + p->em485 = kmalloc(sizeof(struct uart_8250_em485), GFP_KERNEL); + if (p->em485 == NULL) + return -ENOMEM; + + setup_timer(&p->em485->stop_tx_timer, + serial8250_em485_handle_stop_tx, (unsigned long)p); + setup_timer(&p->em485->start_tx_timer, + serial8250_em485_handle_start_tx, (unsigned long)p); + p->em485->active_timer = NULL; + + serial8250_em485_rts_after_send(p); + + return 0; +} +EXPORT_SYMBOL_GPL(serial8250_em485_init); + +/** + * serial8250_em485_destroy() - put uart_8250_port into normal state + * @p: uart_8250_port port instance + * + * The function is used to stop rs485 software emulating on the + * &struct uart_8250_port* @p. The function is idempotent, so it is safe to + * call it multiple times. + * + * The function is supposed to be called from .rs485_config callback + * or from any other callback protected with p->port.lock spinlock. + * + * See also serial8250_em485_init() + */ +void serial8250_em485_destroy(struct uart_8250_port *p) +{ + if (p->em485 == NULL) + return; + + del_timer(&p->em485->start_tx_timer); + del_timer(&p->em485->stop_tx_timer); + + kfree(p->em485); + p->em485 = NULL; +} +EXPORT_SYMBOL_GPL(serial8250_em485_destroy); + /* * These two wrappers ensure that enable_runtime_pm_tx() can be called more than * once and disable_runtime_pm_tx() will still disable RPM because the fifo is @@ -1317,7 +1399,56 @@ static void serial8250_stop_rx(struct uart_port *port) serial8250_rpm_put(up); } -static inline void __stop_tx(struct uart_8250_port *p) +static void __do_stop_tx_rs485(struct uart_8250_port *p) +{ + if (!p->em485) + return; + + serial8250_em485_rts_after_send(p); + /* + * Empty the RX FIFO, we are not interested in anything + * received during the half-duplex transmission. + */ + if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) + serial8250_clear_fifos(p); +} + +static void serial8250_em485_handle_stop_tx(unsigned long arg) +{ + struct uart_8250_port *p = (struct uart_8250_port *)arg; + struct uart_8250_em485 *em485 = p->em485; + unsigned long flags; + + spin_lock_irqsave(&p->port.lock, flags); + if (em485 && + em485->active_timer == &em485->stop_tx_timer) { + __do_stop_tx_rs485(p); + em485->active_timer = NULL; + } + spin_unlock_irqrestore(&p->port.lock, flags); +} + +static void __stop_tx_rs485(struct uart_8250_port *p) +{ + struct uart_8250_em485 *em485 = p->em485; + + if (!em485) + return; + + /* + * __do_stop_tx_rs485 is going to set RTS according to config + * AND flush RX FIFO if required. + */ + if (p->port.rs485.delay_rts_after_send > 0) { + em485->active_timer = &em485->stop_tx_timer; + mod_timer(&em485->stop_tx_timer, jiffies + + p->port.rs485.delay_rts_after_send * HZ / 1000); + } else { + __do_stop_tx_rs485(p); + } +} + +static inline void __do_stop_tx(struct uart_8250_port *p) { if (p->ier & UART_IER_THRI) { p->ier &= ~UART_IER_THRI; @@ -1326,6 +1457,28 @@ static inline void __stop_tx(struct uart_8250_port *p) } } +static inline void __stop_tx(struct uart_8250_port *p) +{ + struct uart_8250_em485 *em485 = p->em485; + + if (em485) { + unsigned char lsr = serial_in(p, UART_LSR); + /* + * To provide required timeing and allow FIFO transfer, + * __stop_tx_rs485 must be called only when both FIFO and + * shift register are empty. It is for device driver to enable + * interrupt on TEMT. + */ + if ((lsr & BOTH_EMPTY) != BOTH_EMPTY) + return; + + del_timer(&em485->start_tx_timer); + em485->active_timer = NULL; + } + __do_stop_tx(p); + __stop_tx_rs485(p); +} + static void serial8250_stop_tx(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); @@ -1343,12 +1496,10 @@ static void serial8250_stop_tx(struct uart_port *port) serial8250_rpm_put(up); } -static void serial8250_start_tx(struct uart_port *port) +static inline void __start_tx(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); - serial8250_rpm_get_tx(up); - if (up->dma && !up->dma->tx_dma(up)) return; @@ -1374,6 +1525,70 @@ static void serial8250_start_tx(struct uart_port *port) } } +static inline void start_tx_rs485(struct uart_port *port) +{ + struct uart_8250_port *up = up_to_u8250p(port); + struct uart_8250_em485 *em485 = up->em485; + unsigned char mcr; + + if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) + serial8250_stop_rx(&up->port); + + del_timer(&em485->stop_tx_timer); + em485->active_timer = NULL; + + mcr = serial_in(up, UART_MCR); + if (!!(up->port.rs485.flags & SER_RS485_RTS_ON_SEND) != + !!(mcr & UART_MCR_RTS)) { + if (up->port.rs485.flags & SER_RS485_RTS_ON_SEND) + mcr |= UART_MCR_RTS; + else + mcr &= ~UART_MCR_RTS; + serial_out(up, UART_MCR, mcr); + + if (up->port.rs485.delay_rts_before_send > 0) { + em485->active_timer = &em485->start_tx_timer; + mod_timer(&em485->start_tx_timer, jiffies + + up->port.rs485.delay_rts_before_send * HZ / 1000); + return; + } + } + + __start_tx(port); +} + +static void serial8250_em485_handle_start_tx(unsigned long arg) +{ + struct uart_8250_port *p = (struct uart_8250_port *)arg; + struct uart_8250_em485 *em485 = p->em485; + unsigned long flags; + + spin_lock_irqsave(&p->port.lock, flags); + if (em485 && + em485->active_timer == &em485->start_tx_timer) { + __start_tx(&p->port); + em485->active_timer = NULL; + } + spin_unlock_irqrestore(&p->port.lock, flags); +} + +static void serial8250_start_tx(struct uart_port *port) +{ + struct uart_8250_port *up = up_to_u8250p(port); + struct uart_8250_em485 *em485 = up->em485; + + serial8250_rpm_get_tx(up); + + if (em485 && + em485->active_timer == &em485->start_tx_timer) + return; + + if (em485) + start_tx_rs485(port); + else + __start_tx(port); +} + static void serial8250_throttle(struct uart_port *port) { port->throttle(port); diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index faa0e03..4348797 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -76,6 +76,12 @@ struct uart_8250_ops { void (*release_irq)(struct uart_8250_port *); }; +struct uart_8250_em485 { + struct timer_list start_tx_timer; /* "rs485 start tx" timer */ + struct timer_list stop_tx_timer; /* "rs485 stop tx" timer */ + struct timer_list *active_timer; /* pointer to active timer */ +}; + /* * This should be used by drivers which want to register * their own 8250 ports without registering their own @@ -122,6 +128,8 @@ struct uart_8250_port { /* 8250 specific callbacks */ int (*dl_read)(struct uart_8250_port *); void (*dl_write)(struct uart_8250_port *, int); + + struct uart_8250_em485 *em485; }; static inline struct uart_8250_port *up_to_u8250p(struct uart_port *up) -- cgit v0.12 -- To unsubscribe, e-mail: opensuse-kernel+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-kernel+owner@opensuse.org

From: "Matwey V. Kornilov" <matwey@sai.msu.ru> Formally, currently there is no memory leak, but if serial8250_ports[line] is reused with other 8250 driver, then em485 will be already activated and it will cause issues. Fixes: e490c9144cfa ("tty: Add software emulated RS485 support for 8250") Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Patch-mainline: Queued in tty-next for 4.6-rc1 Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git Git-commit: bf2a0be45ffc5ab706f9be71a2cdc3f4600cb444 Signed-off-by: Matwey V. Kornilov <matwey.kornilov@gmail.com> --- drivers/tty/serial/8250/8250_core.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 7775221..2f4f5ee 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1074,6 +1074,15 @@ void serial8250_unregister_port(int line) struct uart_8250_port *uart = &serial8250_ports[line]; mutex_lock(&serial_mutex); + + if (uart->em485) { + unsigned long flags; + + spin_lock_irqsave(&uart->port.lock, flags); + serial8250_em485_destroy(uart); + spin_unlock_irqrestore(&uart->port.lock, flags); + } + uart_remove_one_port(&serial8250_reg, &uart->port); if (serial8250_isa_devs) { uart->port.flags &= ~UPF_BOOT_AUTOCONF; -- cgit v0.12 -- To unsubscribe, e-mail: opensuse-kernel+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-kernel+owner@opensuse.org