1 files changed, 124 insertions, 0 deletions
diff --git a/src/graphics/core.S b/src/graphics/core.S
new file mode 100644
index 0000000..3851c0e
--- /dev/null
+++ b/src/graphics/core.S
@@ -0,0 +1,124 @@
+.section .text
+.globl init_graphics
+init_graphics:
+	push {lr}
+	@ set Video Controller resolution to 640x480x16bit
+	@ 16-bit, cause the 8-bit depth needs a palette
+	ldr r1, =vc_set_res
+	bl  mb0_c8_write
+	bl  mb0_c8_read
+	tst r0, #0x80000000
+	beq .vc_init_fail
+
+	@ get VC framebuffer address
+	ldr r1, =vc_alloc_fb
+	bl  mb0_c8_write
+	bl  mb0_c8_read
+	tst r0, #0x80000008
+	beq .vc_init_fail
+
+	@ check if the address is correct
+	ldr r0, [r1, #20]
+	cmp r0, #0
+	beq .vc_init_fail
+
+	@ draw "NO OS" text
+	@bl vc_draw_no_os_bmp
+	ldr r1, =vram_base
+	str r0, [r1]
+	pop {pc}
+
+.vc_init_fail:
+	ldr r1, =txt_vc_fail
+	bl uart_string
+	pop {pc}
+
+.globl draw_pix
+draw_pix:
+	push {lr, r0, r1, r2, r3, r4}
+	ldr r4, =vram_base
+	ldr r4, [r4]
+	mov r3, #2
+	mul r0, r3
+	add r4, r0
+	push {r2}
+	mov r2, #640
+	mul r2, r3
+	mul r3, r1, r2
+	add r4, r3
+	pop {r1}
+	str r1, [r4]
+	pop {pc, r0, r1, r2,  r3, r4}
+
+@@@@@@@@@@@@@@@ VC @@@@@@@@@@@@@@
+
+.equ MBOX0, 0x3f00b880
+
+@ writes to mailbox #0, channel 8
+@ r1 - message
+mb0_c8_write:
+	message .req r1
+	mailbox .req r3
+	status  .req r2
+
+	ldr mailbox, =MBOX0
+.mb0_full:
+	ldr status, [mailbox, #0x18]
+	tst status, #0x80000000  @ mailbox full flag
+	bne .mb0_full 
+	add message, #8          @ channel 8
+	str message, [mailbox, #0x20] @ write addr
+	sub message, #8
+
+	.unreq mailbox
+	.unreq message
+	.unreq status
+	mov pc, lr
+
+@ reads from mailbox #0, channel 8
+@ r1 - message
+@ returns status in r0
+mb0_c8_read:
+	message .req r1
+	mailbox .req r2
+	status  .req r3
+	value   .req r4
+
+	ldr mailbox, =MBOX0
+.mb0_empty:
+	ldr status, [mailbox, #0x18] 
+	tst status, #0x40000000  @ mailbox empty flag
+	bne .mb0_empty
+
+	ldr value, [mailbox] @ check if the message channel is 8
+	and r0, value, #0xf
+	teq r0, #8
+	bne .mb0_empty
+
+	ldr r0, [message, #4] 
+	.unreq message
+	.unreq mailbox
+	.unreq status
+	.unreq value
+	mov pc, lr
+
+@ raspi mailbox requests, must be padded to 16 bytes
+.align 4
+vc_set_res:  .word 80, 0                      @ total size, code (0=req)
+	.word 0x00048003, 8, 8, 640, 480 @ set physical size (640x480)
+	.word 0x00048004, 8, 8, 640, 480 @ set virtual size (640x480)
+	.word 0x00048005, 4, 4, 16       @ set depth (16-bit)
+	.word 0, 0, 0, 0                 @ end tag & padding
+
+vc_alloc_fb: .word 32, 0                      @ total size, code (0=req)
+	.word 0x00040001, 8, 4, 16, 0    @ allocate framebuffer
+	.word 0                          @ end tag & padding
+
+.align 2
+txt_welcome: .asciz "No OS installed\r\n"
+txt_vc_fail: .asciz "VC initialization failed\r\n"
+
+.align 2
+.globl vram_base
+vram_base: .word 0,0
+vmem: .word 0xFFFF