From be4b0281956c5cae4f63f31f11d07625a6988766 Mon Sep 17 00:00:00 2001 From: Paul Walmsley Date: Wed, 25 Jan 2012 19:50:52 -0700 Subject: tty: serial: OMAP: block idle while the UART is transferring data in PIO mode Prevent OMAP UARTs from going idle while they are still transferring data in PIO mode. This works around an oversight in the OMAP UART hardware present in OMAP34xx and earlier: an idle UART won't send a wakeup when the TX FIFO threshold is reached. This causes long delays during data transmission when the MPU powerdomain enters a low-power mode. The MPU interrupt controller is not able to respond to interrupts when it's in a low-power state, so the TX buffer is not refilled until another wakeup event occurs. This fix changes the erratum i291 DMA idle workaround. Rather than toggling between force-idle and no-idle, it will toggle between smart-idle and no-idle. The important part of the workaround is the no-idle part, so this shouldn't result in any change in behavior. This fix should work on all OMAP UARTs. Future patches intended for the 3.4 merge window will make this workaround conditional on a "feature" flag, and will use the OMAP36xx+ TX event wakeup support. Thanks to Kevin Hilman for mentioning the erratum i291 workaround, which led to the development of this approach. Signed-off-by: Paul Walmsley Cc: Alan Cox Cc: Tomi Valkeinen Acked-by: Govindraj.R Reviewed-by: Kevin Hilman Tested-by: Kevin Hilman Signed-off-by: Greg Kroah-Hartman --- arch/arm/mach-omap2/serial.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'arch') diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c index 247d89478f24..f590afc1f673 100644 --- a/arch/arm/mach-omap2/serial.c +++ b/arch/arm/mach-omap2/serial.c @@ -107,18 +107,18 @@ static void omap_uart_set_noidle(struct platform_device *pdev) omap_hwmod_set_slave_idlemode(od->hwmods[0], HWMOD_IDLEMODE_NO); } -static void omap_uart_set_forceidle(struct platform_device *pdev) +static void omap_uart_set_smartidle(struct platform_device *pdev) { struct omap_device *od = to_omap_device(pdev); - omap_hwmod_set_slave_idlemode(od->hwmods[0], HWMOD_IDLEMODE_FORCE); + omap_hwmod_set_slave_idlemode(od->hwmods[0], HWMOD_IDLEMODE_SMART); } #else static void omap_uart_enable_wakeup(struct platform_device *pdev, bool enable) {} static void omap_uart_set_noidle(struct platform_device *pdev) {} -static void omap_uart_set_forceidle(struct platform_device *pdev) {} +static void omap_uart_set_smartidle(struct platform_device *pdev) {} #endif /* CONFIG_PM */ #ifdef CONFIG_OMAP_MUX @@ -349,7 +349,7 @@ void __init omap_serial_init_port(struct omap_board_data *bdata, omap_up.uartclk = OMAP24XX_BASE_BAUD * 16; omap_up.flags = UPF_BOOT_AUTOCONF; omap_up.get_context_loss_count = omap_pm_get_dev_context_loss_count; - omap_up.set_forceidle = omap_uart_set_forceidle; + omap_up.set_forceidle = omap_uart_set_smartidle; omap_up.set_noidle = omap_uart_set_noidle; omap_up.enable_wakeup = omap_uart_enable_wakeup; omap_up.dma_rx_buf_size = info->dma_rx_buf_size; -- cgit v1.2.3