>From OMAP4430 ES2.0 onwards if uart is configured in dma mode we need to set uart tx threshold value using the new register UART_TX_DMA_THRESHOLD, this register can used if UART_MDR3 bit(2) is set. We have to ensure tx_threshold + tx_trigger <= 63 from es2.0 onwards. By default we are using tx_trigger of 1 so we can set threshold to 62 to satisfy above criteria. Without the threshold setting we hit dma_sync lost errors on tx channel leading to data loss on rx side
Signed-off-by: Govindraj.R <[email protected]> --- arch/arm/mach-omap2/serial.c | 4 ++++ arch/arm/plat-omap/include/plat/omap-serial.h | 11 +++++++++++ drivers/tty/serial/omap-serial.c | 5 +++++ 3 files changed, 20 insertions(+), 0 deletions(-) diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c index 0a95c95..437fc0b 100644 --- a/arch/arm/mach-omap2/serial.c +++ b/arch/arm/mach-omap2/serial.c @@ -401,6 +401,10 @@ void __init omap_serial_init_port(struct omap_board_data *bdata, if (bdata->id == omap_uart_con_id) pdata->console_uart = true; + if (pdata->dma_enabled && + cpu_is_omap44xx() && omap_rev() > OMAP4430_REV_ES1_0) + pdata->errata |= OMAP4_UART_ERRATA_i659_TX_THR; + od = omap_device_build(name, bdata->id, oh, pdata, sizeof(*pdata), omap_uart_latency, ARRAY_SIZE(omap_uart_latency), false); diff --git a/arch/arm/plat-omap/include/plat/omap-serial.h b/arch/arm/plat-omap/include/plat/omap-serial.h index 69e6d4b..0d10f72 100644 --- a/arch/arm/plat-omap/include/plat/omap-serial.h +++ b/arch/arm/plat-omap/include/plat/omap-serial.h @@ -56,12 +56,23 @@ #define DEFAULT_RXDMA_BUFSIZE 4096 /* RX DMA buffer size */ #define DEFAULT_AUTOSUSPEND_DELAY (30 * HZ) /* Runtime autosuspend (msecs) */ +/* + * (Errata i659) - From OMAP4430 ES 2.0 onwards set + * tx_threshold while using UART in DMA Mode + * and ensure tx_threshold + tx_trigger <= 63 + */ +#define UART_MDR3 0x20 +#define UART_TX_DMA_THRESHOLD 0x21 +#define SET_DMA_TX_THRESHOLD BIT(2) +/* Setting TX Threshold Level to 62 */ +#define TX_FIFO_THR_LVL 0x3E #define OMAP_MAX_HSUART_PORTS 4 #define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA #define UART_ERRATA_i202_MDR1_ACCESS BIT(0) +#define OMAP4_UART_ERRATA_i659_TX_THR BIT(1) struct omap_uart_port_info { bool dma_enabled; /* To specify DMA Mode */ diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c index dbe76f3..a9645ac 100644 --- a/drivers/tty/serial/omap-serial.c +++ b/drivers/tty/serial/omap-serial.c @@ -818,6 +818,11 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios, serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B); if (up->use_dma) { + if (up->errata & OMAP4_UART_ERRATA_i659_TX_THR) { + serial_out(up, UART_MDR3, SET_DMA_TX_THRESHOLD); + serial_out(up, UART_TX_DMA_THRESHOLD, TX_FIFO_THR_LVL); + } + serial_out(up, UART_TI752_TLR, 0); serial_out(up, UART_OMAP_SCR, (UART_FCR_TRIGGER_4 | UART_FCR_TRIGGER_8)); -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
