Add a specific serial driver for Intel MID platforms.
It has special fractional divider which can be programmed via UART_PS, UART_MUL, and UART_DIV registers.
The UART clock is calculated as
UART clock = XTAL * UART_MUL / UART_DIV
The baudrate is calculated as
baud rate = UART clock / UART_PS / DLAB
Initialize fractional divider correctly for Intel Edison platform.
For backward compatibility we have to set initial DLAB value to 16 and speed to 115200 baud, where initial frequency is 29491200Hz, and XTAL frequency is 38.4MHz.
Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com --- drivers/serial/Kconfig | 9 +++++ drivers/serial/Makefile | 1 + drivers/serial/serial_intel_mid.c | 69 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 79 insertions(+) create mode 100644 drivers/serial/serial_intel_mid.c
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig index b11f3ff89e..99dcdeb00d 100644 --- a/drivers/serial/Kconfig +++ b/drivers/serial/Kconfig @@ -347,6 +347,15 @@ config SYS_NS16550 be used. It can be a constant or a function to get clock, eg, get_serial_clock().
+config INTEL_MID_SERIAL + bool "Intel MID platform UART support" + depends on DM_SERIAL && OF_CONTROL + depends on INTEL_MID + select SYS_NS16550 + help + Select this to enable a UART for Intel MID platforms. + This uses the ns16550 driver as a library. + config ROCKCHIP_SERIAL bool "Rockchip on-chip UART support" depends on DM_SERIAL && SPL_OF_PLATDATA diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile index 8430668bf9..abd9dea4dc 100644 --- a/drivers/serial/Makefile +++ b/drivers/serial/Makefile @@ -28,6 +28,7 @@ obj-$(CONFIG_S5P) += serial_s5p.o obj-$(CONFIG_MXC_UART) += serial_mxc.o obj-$(CONFIG_PXA_SERIAL) += serial_pxa.o obj-$(CONFIG_MESON_SERIAL) += serial_meson.o +obj-$(CONFIG_INTEL_MID_SERIAL) += serial_intel_mid.o ifdef CONFIG_SPL_BUILD obj-$(CONFIG_ROCKCHIP_SERIAL) += serial_rockchip.o endif diff --git a/drivers/serial/serial_intel_mid.c b/drivers/serial/serial_intel_mid.c new file mode 100644 index 0000000000..777c09d6d2 --- /dev/null +++ b/drivers/serial/serial_intel_mid.c @@ -0,0 +1,69 @@ +/* + * Copyright (c) 2017 Intel Corporation + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <common.h> +#include <dm.h> +#include <ns16550.h> +#include <serial.h> + +/* + * The UART clock is calculated as + * + * UART clock = XTAL * UART_MUL / UART_DIV + * + * The baudrate is calculated as + * + * baud rate = UART clock / UART_PS / DLAB + */ +#define UART_PS 0x30 +#define UART_MUL 0x34 +#define UART_DIV 0x38 + +static void mid_writel(struct ns16550_platdata *plat, int offset, int value) +{ + unsigned char *addr; + + offset *= 1 << plat->reg_shift; + addr = (unsigned char *)plat->base + offset; + + writel(value, addr + plat->reg_offset); +} + +static int mid_serial_probe(struct udevice *dev) +{ + struct ns16550_platdata *plat = dev_get_platdata(dev); + + /* + * Initialize fractional divider correctly for Intel Edison + * platform. + * + * For backward compatibility we have to set initial DLAB value + * to 16 and speed to 115200 baud, where initial frequency is + * 29491200Hz, and XTAL frequency is 38.4MHz. + */ + mid_writel(plat, UART_MUL, 96); + mid_writel(plat, UART_DIV, 125); + mid_writel(plat, UART_PS, 16); + + return ns16550_serial_probe(dev); +} + +static const struct udevice_id mid_serial_ids[] = { + { .compatible = "intel,mid-uart" }, + {} +}; + +U_BOOT_DRIVER(serial_intel_mid) = { + .name = "serial_intel_mid", + .id = UCLASS_SERIAL, + .of_match = mid_serial_ids, + .ofdata_to_platdata = ns16550_serial_ofdata_to_platdata, + .platdata_auto_alloc_size = sizeof(struct ns16550_platdata), + .priv_auto_alloc_size = sizeof(struct NS16550), + .probe = mid_serial_probe, + .ops = &ns16550_serial_ops, + .flags = DM_FLAG_PRE_RELOC, +};