OMAP3630 and OMAP4430 UART IP blocks have a restriction wrt RX FIFO. Empty RX fifo read causes an abort. OMAP1/2/3 do not have this restriction. Overrigt the default 8250 read handler: mem_serial_in() by a custom handler: serial_in_8250() serial_in_8250() makes sure that RX fifo is not read when empty, on omap4 and 3630 silicons only tested on zoom3(3630) board Signed-off-by: Vikram Pandita <vikram.pandita@xxxxxx> Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> --- v1: initial implementation http://patchwork.kernel.org/patch/60785/ http://patchwork.kernel.org/patch/60786/ v2: incorporate review comments from Alan Cox http://patchwork.kernel.org/patch/60785/ No 8250 driver change required now arch/arm/mach-omap2/serial.c | 28 ++++++++++++++++++++++++++++ 1 files changed, 28 insertions(+), 0 deletions(-) diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c index 2e17b57..362cb82 100644 --- a/arch/arm/mach-omap2/serial.c +++ b/arch/arm/mach-omap2/serial.c @@ -71,6 +71,30 @@ struct omap_uart_state { static LIST_HEAD(uart_list); +static struct omap_uart_state omap_uart[]; +static inline unsigned int serial_read_reg(struct plat_serial8250_port *, int); + +/* + * Overrigt the default 8250 read handler: mem_serial_in() + * Empty RX fifo read causes an abort on omap3630 and omap4 + * This function makes sure that an empty rx fifo is not read on these silicons + * (OMAP1/2/3 are not affected) + */ +static unsigned int serial_in_8250(struct uart_port *up, int offset) +{ + /* Do not read empty UART fifo on omap3630/44xx */ + if ((UART_RX == offset) && + (cpu_is_omap3630() || cpu_is_omap44xx())) { + + unsigned int lsr; + + lsr = serial_read_reg(omap_uart[up->line].p, UART_LSR); + if (!(lsr & UART_LSR_DR)) + return 0; + } + return serial_read_reg(omap_uart[up->line].p, offset); +} + static struct plat_serial8250_port serial_platform_data0[] = { { .mapbase = OMAP_UART1_BASE, @@ -79,6 +103,7 @@ static struct plat_serial8250_port serial_platform_data0[] = { .iotype = UPIO_MEM, .regshift = 2, .uartclk = OMAP24XX_BASE_BAUD * 16, + .serial_in = serial_in_8250, }, { .flags = 0 } @@ -92,6 +117,7 @@ static struct plat_serial8250_port serial_platform_data1[] = { .iotype = UPIO_MEM, .regshift = 2, .uartclk = OMAP24XX_BASE_BAUD * 16, + .serial_in = serial_in_8250, }, { .flags = 0 } @@ -105,6 +131,7 @@ static struct plat_serial8250_port serial_platform_data2[] = { .iotype = UPIO_MEM, .regshift = 2, .uartclk = OMAP24XX_BASE_BAUD * 16, + .serial_in = serial_in_8250, }, { .flags = 0 } @@ -119,6 +146,7 @@ static struct plat_serial8250_port serial_platform_data3[] = { .iotype = UPIO_MEM, .regshift = 2, .uartclk = OMAP24XX_BASE_BAUD * 16, + .serial_in = serial_in_8250, }, { .flags = 0 } -- 1.6.5.1.69.g36942 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
