drivers: imx: crash-console: Add a mxc_crash_console driver
This patch does two main things
- It implements the crash console UART init in assembly, as a
hard-coded 115200 8N1 assumed from the 24 MHz clock.
If the clock setup code has not run yet, this code can't work but,
setting up clocks and clock-gates is way out of scope for this type of
recovery function.
- It adds code to write a character out of the NXP UART without using any
stack-based operations when doing so.
- Provides support for crash console in DCE or DTE mode.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
diff --git a/drivers/imx/uart/imx_crash_uart.S b/drivers/imx/uart/imx_crash_uart.S
new file mode 100644
index 0000000..aa987b3
--- /dev/null
+++ b/drivers/imx/uart/imx_crash_uart.S
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) Linaro 2018 Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include <arch.h>
+#include <asm_macros.S>
+#include <assert_macros.S>
+#include <imx_uart.h>
+#include <platform_def.h>
+
+ .globl imx_crash_uart_init
+ .globl imx_crash_uart_putc
+
+ /* -----------------------------------------------
+ * int imx_crash_uart_init(uintptr_t base_addr,
+ * unsigned int uart_clk, unsigned int baud_rate)
+ * Function to initialize the console without a
+ * C Runtime to print debug information. This
+ * function will be accessed by console_init and
+ * crash reporting.
+ * In: r0 - console base address
+ * r1 - Uart clock in Hz
+ * r2 - Baud rate
+ * Out: return 1 on success else 0 on error
+ * Clobber list : r1, r2, r3, r4
+ * -----------------------------------------------
+ */
+func imx_crash_uart_init
+ /* Free up r1 as a scratch reg */
+ mov r4, r0
+ mov r0, r1
+
+ /* Reset UART via CR2 */
+ add r1, r4, #IMX_UART_CR2_OFFSET
+ movs r3, #0
+ str r3, [r4, #IMX_UART_CR2_OFFSET]
+
+ /* Wait for reset complete */
+__wait_cr2_reset:
+ ldr r3, [r1, #0]
+ ands r3, #IMX_UART_CR2_SRST
+ beq __wait_cr2_reset
+
+ /* Enable UART */
+ movs r3, #IMX_UART_CR1_UARTEN
+ mov r1, r2
+ str r3, [r4, #IMX_UART_CR1_OFFSET]
+
+ /*
+ * Ignore RTC/CTS - disable reset
+ * Magic value #16423 =>
+ * IMX_UART_CR2_IRTS | IMX_UART_CR2_WS | IMX_UART_CR2_TXEN | IMX_UART_CR2_RXEN | IMX_UART_CR2_SRST
+ */
+ movw r3, #16423
+ str r3, [r4, #IMX_UART_CR2_OFFSET]
+
+ /*
+ * No parity, autobaud detect-old, rxdmuxsel=1 (fixed i.mx7)
+ * Magic value => #132
+ * IMX_UART_CR3_ADNIMP | IMX_UART_CR3_RXDMUXSEL
+ */
+ movs r3, #132
+ str r3, [r4, #IMX_UART_CR3_OFFSET]
+
+ /*
+ * Set CTS FIFO trigger to 32 bytes bits 15:10
+ * Magic value => #32768
+ * FIFO trigger bitmask 100000
+ * */
+ mov r3, #32768
+ str r3, [r4, #IMX_UART_CR4_OFFSET]
+
+ /*
+ * TX/RX-thresh = 2 bytes, DCE (bit6 = 0), refclk @24MHz / 4
+ * Magic value #2562
+ * IMX_UART_FCR_TXTL(TX_RX_THRESH) | IMX_UART_FCR_RXTL(TX_RX_THRESH) | IMX_UART_FCR_RFDIV2
+ */
+ #ifdef IMX_UART_DTE
+ movw r3, #2626
+ #else
+ movw r3, #2562
+ #endif
+ str r3, [r4, #IMX_UART_FCR_OFFSET]
+
+ /* This BIR should be set to 0x0F prior to writing the BMR */
+ movs r3, #15
+ str r3, [r4, #IMX_UART_BIR_OFFSET]
+
+ /* Hard-code to 115200 @ 24 MHz */
+ movs r0, #104
+ str r0, [r4, #IMX_UART_BMR_OFFSET]
+
+ /* Indicate success */
+ movs r0, #1
+ bx lr
+endfunc imx_crash_uart_init
+
+ /* --------------------------------------------------------
+ * int imx_crash_uart_putc(int c, uintptr_t base_addr)
+ * Function to output a character over the console. It
+ * returns the character printed on success or -1 on error.
+ * In : r0 - character to be printed
+ * r1 - console base address
+ * Out : return -1 on error else return character.
+ * Clobber list : r2
+ * --------------------------------------------------------
+ */
+func imx_crash_uart_putc
+ /* Output specified character to UART shift-register */
+ str r0, [r1, #IMX_UART_TXD_OFFSET]
+
+ /* Wait for transmit IMX_UART_STAT2_OFFSET.IMX_UART_STAT2_TXDC == 1 */
+__putc_spin_ready:
+ ldr r2, [r1, #IMX_UART_STAT2_OFFSET]
+ ands r2, #IMX_UART_STAT2_TXDC
+ beq __putc_spin_ready
+
+ /* Transmit complete do we need to fixup \n to \n\r */
+ cmp r0, #10
+ beq __putc_fixup_lf
+
+ /* No fixup necessary - exit here */
+ movs r0, #0
+ bx lr
+
+ /* Fixup \n to \n\r */
+__putc_fixup_lf:
+ movs r0, #13
+ b imx_crash_uart_putc
+endfunc imx_crash_uart_putc