New patch to review for coreboot: mb/lowrisc/nexys4ddr: Actually fix the UART clock setup

[Jonathan Neuschäfer]

Jonathan Neuschäfer ([e-mail]) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/17188

-gerrit

commit 12cf0cdcfbd140db191009f665c10127a4bae687
Author: Jonathan Neuschäfer 
Date:   Sat Oct 29 21:48:18 2016 +0200

mb/lowrisc/nexys4ddr: Actually fix the UART clock setup

Ron's code calculated the DLL and DLM registers of the 8250 UART, but
    that's the job of the UART driver. uart_input_clock_divider isn't needed
    anymore because the default value of 16 works.

As a bonus, the baud rate can now be selected in Kconfig, instead of
    being hardcoded at 115200.

TEST=Booted the board at 9600 and 115200 baud.

Change-Id: I3d5e49568b798a6a6d944db1161def7d0a2d3b48
    Signed-off-by: Jonathan Neuschäfer 
---
 src/mainboard/lowrisc/nexys4ddr/Kconfig |  1 -
 src/mainboard/lowrisc/nexys4ddr/uart.c  | 13 ++-----------
 2 files changed, 2 insertions(+), 12 deletions(-)

diff --git a/src/mainboard/lowrisc/nexys4ddr/Kconfig b/src/mainboard/lowrisc/nexys4ddr/Kconfig
index f0a3637..5a6bfb2 100644
--- a/src/mainboard/lowrisc/nexys4ddr/Kconfig
+++ b/src/mainboard/lowrisc/nexys4ddr/Kconfig
@@ -21,7 +21,6 @@ config BOARD_SPECIFIC_OPTIONS # dummy
    select DRIVERS_UART_8250MEM
    select BOOT_DEVICE_NOT_SPI_FLASH
    select UART_OVERRIDE_REFCLK
-	select UART_OVERRIDE_INPUT_CLOCK_DIVIDER

config MAINBOARD_DIR
    string
diff --git a/src/mainboard/lowrisc/nexys4ddr/uart.c b/src/mainboard/lowrisc/nexys4ddr/uart.c
index e3c233f80..d19ce52 100644
--- a/src/mainboard/lowrisc/nexys4ddr/uart.c
+++ b/src/mainboard/lowrisc/nexys4ddr/uart.c
@@ -24,17 +24,8 @@ uintptr_t uart_platform_base(int idx)
    return (uintptr_t) 0x42000000;
 }

-/* these are currently not quite right but they are here for reference
- * and will be fixed when lowrisc gives us a standard clock
- * and set of values. */
-// divisor = clk_freq / (16 * Baud)
-unsigned int uart_input_clock_divider(void)
-{
-	return (25 * 1000 * 1000u / (16u * 115200u)) % 0x100;
-}
-
-// System clock 25 MHz, 115200 baud rate
+/* The clock which the UART is based on */
 unsigned int uart_platform_refclk(void)
 {
-	return (25 * 1000 * 1000u / (16u * 115200u)) >> 8;
+	return 25 * MHz;
 }