From e03d37d85909fd9b09e78087c57b45972a7664ad Mon Sep 17 00:00:00 2001 From: Santosh Shilimkar Date: Thu, 18 Feb 2010 08:59:06 +0000 Subject: [PATCH] omap3/4: uart: fix full-fifo write abort This patch is addition to the already merged commit on non-empty uart fifo read abort. "ce13d4716a276f4331d78ba28a5093a63822ab95" OMAP3630 and OMAP4430 UART IP blocks have a restriction on TX FIFO too. If you try to write to the tx fifo when it is full, the system aborts. More details on this thread are here: http://www.mail-archive.com/linux-omap@vger.kernel.org/msg19447.html This can be easily reproducible by not suppressing interconnect errors or long duration testing where continuous prints over console from multiple threads. This patch is addressing the issue by ensuring that write is not issued while fifo is full. A timeout is added to avoid any hang on fifo-full for 10 mS which is unlikely case. Patch is validated on OMAP3630 and OMAP4 SDP. V2 version removed the additional 1 uS on every TX as per Tony's suggestion Signed-off-by: Woodruff Richard Signed-off-by: Santosh Shilimkar CC: Ghorai Sukumar Reviewed-by: Paul Walmsley Signed-off-by: Tony Lindgren --- arch/arm/mach-omap2/serial.c | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c index 5f3035e..b79bc89 100644 --- a/arch/arm/mach-omap2/serial.c +++ b/arch/arm/mach-omap2/serial.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include @@ -160,6 +161,13 @@ static inline unsigned int serial_read_reg(struct plat_serial8250_port *up, return (unsigned int)__raw_readb(up->membase + offset); } +static inline void __serial_write_reg(struct uart_port *up, int offset, + int value) +{ + offset <<= up->regshift; + __raw_writeb(value, up->membase + offset); +} + static inline void serial_write_reg(struct plat_serial8250_port *p, int offset, int value) { @@ -620,6 +628,20 @@ static unsigned int serial_in_override(struct uart_port *up, int offset) return __serial_read_reg(up, offset); } +static void serial_out_override(struct uart_port *up, int offset, int value) +{ + unsigned int status, tmout = 10000; + + status = __serial_read_reg(up, UART_LSR); + while (!(status & UART_LSR_THRE)) { + /* Wait up to 10ms for the character(s) to be sent. */ + if (--tmout == 0) + break; + udelay(1); + status = __serial_read_reg(up, UART_LSR); + } + __serial_write_reg(up, offset, value); +} void __init omap_serial_early_init(void) { int i; @@ -721,11 +743,14 @@ void __init omap_serial_init_port(int port) * omap3xxx: Never read empty UART fifo on UARTs * with IP rev >=0x52 */ - if (cpu_is_omap44xx()) + if (cpu_is_omap44xx()) { uart->p->serial_in = serial_in_override; - else if ((serial_read_reg(uart->p, UART_OMAP_MVER) & 0xFF) - >= UART_OMAP_NO_EMPTY_FIFO_READ_IP_REV) + uart->p->serial_out = serial_out_override; + } else if ((serial_read_reg(uart->p, UART_OMAP_MVER) & 0xFF) + >= UART_OMAP_NO_EMPTY_FIFO_READ_IP_REV) { uart->p->serial_in = serial_in_override; + uart->p->serial_out = serial_out_override; + } } /** -- 2.7.4