From 7388c270069c2d1418539bca1d2789a6d468ecc2 Mon Sep 17 00:00:00 2001
From: Jacques Comeaux <jacquesrcomeaux@protonmail.com>
Date: Mon, 20 May 2024 23:19:14 -0500
Subject: Make shared object for setup routines

---
 setup/uart.s | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 setup/uart.s

(limited to 'setup/uart.s')

diff --git a/setup/uart.s b/setup/uart.s
new file mode 100644
index 0000000..d4b81d2
--- /dev/null
+++ b/setup/uart.s
@@ -0,0 +1,58 @@
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+.equ RESETS_BASE, 0x4000c000
+.equ RESET_OFST,      0x0
+.equ RESET_DONE_OFST, 0x8
+
+.equ IO_BANK0_BASE, 0x40014000
+.equ GPIO0_CTRL_OFST, 0x04
+.equ GPIO1_CTRL_OFST, 0x0c
+
+.equ UART0_BASE, 0x40034000
+.equ UARTDR_OFST,     0x00
+.equ UARTFR_OFST,     0x18
+.equ UARTIBRD_OFST,   0x24
+.equ UARTFBRD_OFST,   0x28
+.equ UARTLCR_H_OFST,  0x2c
+.equ UARTCR_OFST,     0x30
+
+.equ ATOMIC_SET,    0x2000
+.equ ATOMIC_CLEAR,  0x3000
+
+.type setup_uart, %function
+.global setup_uart
+
+setup_uart:
+
+  // Deassert reset
+  ldr r1, =(RESETS_BASE + ATOMIC_CLEAR)
+  movs r0, 0b1 // UART0
+  lsls r0, 22
+  str r0, [r1, RESET_OFST]
+  ldr r1, =RESETS_BASE
+1:
+  ldr r2, [r1, RESET_DONE_OFST]
+  tst r2, r0
+  beq 1b
+
+  // Configure and enable
+  ldr r1, =UART0_BASE
+  movs r0, 6
+  str r0, [r1, UARTIBRD_OFST]
+  movs r0, 33
+  str r0, [r1, UARTFBRD_OFST]
+  movs r0, 0b111 << 4 // 0b11 = word len 8 bits, 0b1 = FIFO enabled
+  str r0, [r1, UARTLCR_H_OFST]
+  ldr r1, =(UART0_BASE + ATOMIC_SET)
+  movs r0, 0b1 // UART enable
+  str r0, [r1, UARTCR_OFST]
+
+  // Configure GPIO 0 and 1 as TX and RX
+  ldr r1, =IO_BANK0_BASE
+  movs r0, 2 // UART function
+  str r0, [r1, GPIO0_CTRL_OFST]
+  str r0, [r1, GPIO1_CTRL_OFST]
+
+  bx lr
-- 
cgit v1.2.3