From: Deepak K <deepak.k@xxxxxx> Errata i202 (OMAP3430 - 1.12, OMAP3630 - 1.6): UART module MDR1 register access can cause a dummy underrun condition which could result in a freeze in the case of IrDA communication or if used as UART, corrupted data. Workaround is as follows for everytime MDR1 register is changed: * setup all required UART registers * setup MDR1.MODE_SELECT bit field * Wait 5 L4 clk cycles + 5 UART functional clock cycles * Clear the Tx and RX fifo using FCR register Note: The following step is not done as I am assuming it is not needed due to reconfiguration being done and there is no halted operation perse. * Read if required, the RESUME register to resume halted operation Based on an earlier patch at: http://git.omapzoom.org/?p=kernel/omap.git;a=commitdiff;h=42d4a342c009bd9727c100abc8a4bc3063c22f0c Signed-off-by: Deepak K <deepak.k@xxxxxx> Signed-off-by: Nishanth Menon <nm@xxxxxx> Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx> --- arch/arm/mach-omap2/serial.c | 52 ++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 49 insertions(+), 3 deletions(-) diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c index 009b63f..566e991 100644 --- a/arch/arm/mach-omap2/serial.c +++ b/arch/arm/mach-omap2/serial.c @@ -38,6 +38,7 @@ #define UART_OMAP_WER 0x17 /* Wake-up enable register */ #define UART_ERRATA_FIFO_FULL_ABORT (0x1 << 0) +#define UART_ERRATA_i202_MDR1_ACCESS (0x1 << 1) /* * NOTE: By default the serial timeout is disabled as it causes lost characters @@ -184,6 +185,42 @@ static inline void __init omap_uart_reset(struct omap_uart_state *uart) #if defined(CONFIG_PM) && defined(CONFIG_ARCH_OMAP3) +/* + * Work Around for Errata i202 (3430 - 1.12, 3630 - 1.6) + * The access to uart register after MDR1 Access + * causes UART to corrupt data. + * + * Need a delay = + * 5 L4 clock cycles + 5 UART functional clock cycle (@48MHz = ~0.2uS) + * give 10 times as much + */ +static void omap_uart_mdr1_errataset(struct omap_uart_state *uart, u8 mdr1_val, + u8 fcr_val) +{ + struct plat_serial8250_port *p = uart->p; + u8 timeout = 255; + + serial_write_reg(p, UART_OMAP_MDR1, mdr1_val); + udelay(2); + serial_write_reg(p, UART_FCR, fcr_val | UART_FCR_CLEAR_XMIT | + UART_FCR_CLEAR_RCVR); + /* + * Wait for FIFO to empty: when empty, RX_FIFO_E bit is 0 and + * TX_FIFO_E bit is 1. + */ + while (UART_LSR_THRE != (serial_read_reg(p, UART_LSR) & + (UART_LSR_THRE | UART_LSR_DR))) { + timeout--; + if (!timeout) { + /* Should *never* happen. we warn and carry on */ + dev_crit(&uart->pdev.dev, "Errata i202: timedout %x\n", + serial_read_reg(p, UART_LSR)); + break; + } + udelay(1); + } +} + static void omap_uart_save_context(struct omap_uart_state *uart) { u16 lcr = 0; @@ -221,7 +258,10 @@ static void omap_uart_restore_context(struct omap_uart_state *uart) uart->context_valid = 0; - serial_write_reg(p, UART_OMAP_MDR1, 0x7); + if (uart->errata & UART_ERRATA_i202_MDR1_ACCESS) + omap_uart_mdr1_errataset(uart, 0x07, 0xA0); + else + serial_write_reg(p, UART_OMAP_MDR1, 0x7); serial_write_reg(p, UART_LCR, 0xBF); /* Config B mode */ efr = serial_read_reg(p, UART_EFR); serial_write_reg(p, UART_EFR, UART_EFR_ECB); @@ -234,14 +274,16 @@ static void omap_uart_restore_context(struct omap_uart_state *uart) serial_write_reg(p, UART_IER, uart->ier); serial_write_reg(p, UART_LCR, 0x80); serial_write_reg(p, UART_MCR, uart->mcr); - serial_write_reg(p, UART_FCR, 0xA1); serial_write_reg(p, UART_LCR, 0xBF); /* Config B mode */ serial_write_reg(p, UART_EFR, efr); serial_write_reg(p, UART_LCR, UART_LCR_WLEN8); serial_write_reg(p, UART_OMAP_SCR, uart->scr); serial_write_reg(p, UART_OMAP_WER, uart->wer); serial_write_reg(p, UART_OMAP_SYSC, uart->sysc); - serial_write_reg(p, UART_OMAP_MDR1, 0x00); /* UART 16x mode */ + if (uart->errata & UART_ERRATA_i202_MDR1_ACCESS) + omap_uart_mdr1_errataset(uart, 0x00, 0xA1); + else + serial_write_reg(p, UART_OMAP_MDR1, 0x00); /* UART 16x mode */ } #else static inline void omap_uart_save_context(struct omap_uart_state *uart) {} @@ -769,6 +811,10 @@ void __init omap_serial_init_port(int port) uart->p->serial_in = serial_in_override; uart->p->serial_out = serial_out_override; } + + /* Enable the MDR1 errata for OMAP3 */ + if (cpu_is_omap34xx()) + uart->errata |= UART_ERRATA_i202_MDR1_ACCESS; } /** -- 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
