From 53f12a42c5059acc3e1139ee31827370d26ea047 Mon Sep 17 00:00:00 2001
From: d00f <8052722+DrDoof@users.noreply.github.com>
Date: Wed, 9 Sep 2026 01:52:12 +0200
Subject: [PATCH] crc16: banked wrapper for cross-bank callers

The lookup tables live in BANK1, so the routine switches the code bank to
reach them with movc and never switches it back. That is the contract the
__naked declaration already implied: same bank or common segment only.
The name now says it.

crc16_bank1 is the routine unchanged. crc16 becomes a __banked wrapper in
BANK1, so a caller from another bank has its own bank put back by
__sdcc_banked_ret. The two existing call sites take the direct path and
pay nothing.
---
 crc16.asm       | 8 +++++++-
 httpd/httpd.c   | 6 +++---
 rtlplayground.c | 4 ++--
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/crc16.asm b/crc16.asm
index 4f1be7ae..f7fa2f9c 100644
--- a/crc16.asm
+++ b/crc16.asm
@@ -3,6 +3,8 @@
 ;
 	.globl 	_crc_value
 	.globl 	_crc16
+	.globl 	_crc16_bank1
+	.globl 	__sdcc_banked_ret
 	.equ	BANK, 0x96
 ;	.equ	DPS, 0x86
 ; Variable in XMEM holding current CRC16 value, being updated
@@ -18,7 +20,7 @@ _crc_value::
 	.area HOME    (CODE)
 	.area CSEG    (CODE)
 ;	.area BANK1   (CODE)
-_crc16:
+_crc16_bank1:
 	mov	BANK, #1
 	push	dph
 	push	dpl
@@ -52,6 +54,10 @@ _crc16:
 
 	.area BANK1   (CODE)
 
+_crc16:
+	lcall	_crc16_bank1
+	ljmp	__sdcc_banked_ret
+
 crc16_table_l:
 	.byte #0x00, #0xc1, #0x81, #0x40, #0x01, #0xc0, #0x80, #0x41
 	.byte #0x01, #0xc0, #0x80, #0x41, #0x00, #0xc1, #0x81, #0x40
diff --git a/httpd/httpd.c b/httpd/httpd.c
index cbb41b93..7eb28185 100644
--- a/httpd/httpd.c
+++ b/httpd/httpd.c
@@ -89,7 +89,7 @@ __xdata uint32_t last_session_use;
 
 extern __xdata uint16_t crc_value;
 __xdata uint16_t crc_final;
-void crc16(__xdata uint8_t *v) __naked;
+void crc16_bank1(__xdata uint8_t *v) __naked;
 
 
 inline uint8_t is_separator(uint8_t c)
@@ -518,7 +518,7 @@ uint8_t stream_upload(void)
 		if (upload_settings.p[upload_settings.bptr] == boundary[bindex]) {
 			if (!bindex)
 				crc_final = crc_value;
-			crc16(upload_settings.p + upload_settings.bptr);
+			crc16_bank1(upload_settings.p + upload_settings.bptr);
 			upload_settings.bptr++;
 			bindex++;
 		} else {
@@ -527,7 +527,7 @@ uint8_t stream_upload(void)
 				write_len += bindex;
 				bindex = 0;
 			}
-			crc16(upload_settings.p + upload_settings.bptr);
+			crc16_bank1(upload_settings.p + upload_settings.bptr);
 			flash_buf[write_len++] = upload_settings.p[upload_settings.bptr++];
 			if (write_len >= FLASH_PAGE_SIZE) {
 				dbg_string("len: "); dbg_short(write_len); dbg_char(' ');
diff --git a/rtlplayground.c b/rtlplayground.c
index bbca65b3..23a3e192 100644
--- a/rtlplayground.c
+++ b/rtlplayground.c
@@ -32,7 +32,7 @@ extern __xdata uint32_t flash_size;
 
 extern __xdata uint16_t crc_value;
 __xdata struct machine_runtime machine_detected;
-void crc16(__xdata uint8_t *v) __naked;
+void crc16_bank1(__xdata uint8_t *v) __naked;
 void flash_default_config(void);
 void early_boot_handle_button(void);
 
@@ -2095,7 +2095,7 @@ void check_and_flash_update_image(void)
 			flash_read_bulk(flash_buf);
 			bptr = flash_buf;
 			for (j = 0; j < FLASH_BUF_SIZE; j++) {
-				crc16(bptr++);
+				crc16_bank1(bptr++);
 			}
 			source += FLASH_BUF_SIZE;
 			if (i%16 == 0) write_char('.');