>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 <govindraj.raja@xxxxxx>
---
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
--
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