From: Deepak K <deepak.k@xxxxxx> Original patch: http://git.omapzoom.org/?p=kernel/omap.git;a=commitdiff;h=42d4a342c009bd9727c100abc8a4bc3063c22f0c 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 Cc: Govindraj R <govindraj.raja@xxxxxx> Cc: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx> Cc: Tero Kristo <tero.kristo@xxxxxxxxx> Signed-off-by: Deepak K <deepak.k@xxxxxx> Signed-off-by: Nishanth Menon <nm@xxxxxx> --- Note: original patch was done for android kernel, ported and sanity tested arch/arm/mach-omap2/serial.c | 18 +++++++++++++++++- 1 files changed, 17 insertions(+), 1 deletions(-) diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c index 86d3b47..144033f 100644 --- a/arch/arm/mach-omap2/serial.c +++ b/arch/arm/mach-omap2/serial.c @@ -223,6 +223,19 @@ static void omap_uart_restore_context(struct omap_uart_state *uart) uart->context_valid = 0; serial_write_reg(p, UART_OMAP_MDR1, 0x7); + /* + * 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 + */ + udelay(2); + /* TX and RX FIFO Clear; FIFO dis */ + serial_write_reg(p, UART_FCR, 0xA6); + 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); @@ -235,7 +248,6 @@ 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); @@ -243,6 +255,10 @@ static void omap_uart_restore_context(struct omap_uart_state *uart) 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 */ + /* Errata: i202 */ + udelay(2); + /* TX and RX FIFO Clear; FIFO en */ + serial_write_reg(p, UART_FCR, 0xA7); } #else static inline void omap_uart_save_context(struct omap_uart_state *uart) {} -- 1.6.3.3 -- 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
