From c2488d68f0e43a46d63cec038a37308db7290d34 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@linux.intel.com>
Date: Sat, 9 Mar 2019 19:41:58 +0000
Subject: [PATCH] z80sio: Fix a bug in the linc80 logic and add macros for non
 fixed common cases

---
 Kernel/dev/z80sio.s             | 45 ++++++++++++++++++++++++++++++---
 Kernel/platform-linc80/devtty.c |  4 +--
 Kernel/platform-linc80/linc80.s | 12 +++++++++
 3 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/Kernel/dev/z80sio.s b/Kernel/dev/z80sio.s
index 458c60ae..8eef01e0 100644
--- a/Kernel/dev/z80sio.s
+++ b/Kernel/dev/z80sio.s
@@ -20,7 +20,7 @@ sio'X'_rx:
 sio'X'_tx:
 	.ds	128
 
-	.area _COMMONMEM
+	.area _SERIALDATA
 sio'X'_error:
 	.db	0
 sio'X'_rxover:
@@ -54,6 +54,7 @@ sio'X'_rxe:
 ;
 sio'X'_txd:
 	push af
+	switch
 	ld a,(_sio'X'_txl)
 	or a
 	jr z, tx_'X'_none
@@ -70,6 +71,7 @@ sio'X'_txd:
 tx_'X'_none:
 	ld a,#0x28
 	out (CP),a		; silence tx interrupt
+	switchback
 	pop af
 	ei
 	RET
@@ -79,6 +81,7 @@ tx_'X'_none:
 sio'X'_rx_ring:
 	push af
 	push hl
+	switch
 sio'X'_rx_next:
 	in a,(DP)		; read ASAP
 	ld l,a
@@ -106,6 +109,7 @@ sio'X'_rx_next:
 	in a,(CP)		; RR 0
 	rra
 	jr c, sio'X'_rx_next
+	switchback
 	pop hl
 	pop af
 	ei
@@ -114,6 +118,8 @@ sio'X'_rx_next:
 	ld a,(sio'X'_error)
 	or #0x20		; Fake an RX overflow bit
 	ld (sio'X'_rxover),a
+	switchback
+	pop hl
 	pop af
 	ei
 	RET
@@ -124,6 +130,7 @@ sio'X'_status:
 	; CTS or DCD change
 	push af
 	push hl
+	switch
 	; RR0
 	in a,(CP)
 	ld (_sio'X'_state),a
@@ -135,6 +142,7 @@ no_dcd_drop_'X':
 	; Clear the latched values
 	ld a,#0x10
 	out (CP),a
+	switchback
 	pop hl
 	pop af
 	ei
@@ -147,6 +155,7 @@ sio'X'_special:
 	; Parity, RX Overrun, Framing
 	; Probably want to record them, but we at least must clean up
 	push af
+	switch
 	ld a,#1
 	out (CP),a		; RR1 please
 	in a,(CP)		; clear events
@@ -154,6 +163,7 @@ sio'X'_special:
 	; Clear the latched values
 	ld a,#0x30
 	out (CP),a
+	switchback
 	pop af
 	ei
 	RET
@@ -168,6 +178,7 @@ sio'X'_special:
 ;	128 byte ring buffer aligned to upper half (rx is in lower)
 ;
 _sio'X'_txqueue:
+	switch
 	ld a,(_sio'X'_txl)
 	or a
 	jr z, sio'X'_direct_maybe	; if can tx now then do
@@ -182,10 +193,12 @@ sio'X'_queue:
 	set 7,l
 	ld (sio'X'_txe),hl
 	ld l,#0
+	switchback
 	ret
 tx'X'_overflow:
 	; some kind of flag for error
 	ld l,#1
+	switchback
 	ret
 sio'X'_direct_maybe:
 	; check RR
@@ -197,18 +210,19 @@ sio'X'_direct_maybe:
 	; bypass the queue and kickstart the interrupt machine
 	ld a,l
 	out (DP),a
+	switchback
 	ld l,#0
 	ret
 	; Call with DI
 
-_sio'X'_flow_control_off:
+sio'X'_flow_control_off:
 	ld a,#5
 	out(CP),a		; WR 5
 	ld a,(_sio'X'_wr5)
 	out (CP),a		; Turn off RTS
 	ret
 
-_sio'X'_flow_control_on:
+sio'X'_flow_control_on:
 	ld a,#5
 	out(CP),a		; WR 5
 	ld a,(_sio'X'_wr5)
@@ -216,12 +230,25 @@ _sio'X'_flow_control_on:
 	out (CP),a		; Turn off RTS
 	ret
 
+_sio'X'_flow_control_off:
+	switch
+	call sio'X'_flow_control_off
+	switchback
+	ret
+
+_sio'X'_flow_control_on:
+	switch
+	call sio'X'_flow_control_on
+	switchback
+	ret
+
 	; DI required
 	; Returns char in L
 	;
 	; Caller responsible for making post buffer fetch decisions about
 	; RTS
 _sio'X'_rx_get:
+	switch
 	ld a,(_sio'X'_rxl)
 	or a
 	ret z
@@ -234,15 +261,27 @@ _sio'X'_rx_get:
 	ld (sio'X'_rxe),hl
 	scf
 	ld l,a
+	switchback
 	ret
 
 	; DI required
 _sio'X'_error_get:
+	switch
 	ld hl,#sio'X'_error
 	ld a,(hl)
 	ld (hl),#0
 	ld l,a
+	switchback
 	ret
 
+.endm
+
+.macro _sio_read
 
+_sio_read:
+	switch
+	ld a,(hl)
+	ld l,a
+	switchback
+	ret
 .endm
diff --git a/Kernel/platform-linc80/devtty.c b/Kernel/platform-linc80/devtty.c
index 21b57348..4bf1e75c 100644
--- a/Kernel/platform-linc80/devtty.c
+++ b/Kernel/platform-linc80/devtty.c
@@ -143,9 +143,9 @@ void tty_sleeping(uint8_t minor)
 
 ttyready_t tty_writeready(uint8_t minor)
 {
-	if (minor == 1 && sio_txl[1] == 255)
+	if (minor == 1 && sio_txl[1] >= 127)
 		return TTY_READY_SOON;
-	if (minor == 2 && sio_txl[0] == 255)
+	if (minor == 2 && sio_txl[0] >= 127)
 		return TTY_READY_SOON;
 	return TTY_READY_NOW;
 }
diff --git a/Kernel/platform-linc80/linc80.s b/Kernel/platform-linc80/linc80.s
index cbb5a619..697ac34f 100644
--- a/Kernel/platform-linc80/linc80.s
+++ b/Kernel/platform-linc80/linc80.s
@@ -325,6 +325,18 @@ _siob_txl:
 
 sio_ports a
 sio_ports b
+
+	.area _COMMONMEM
+
+;
+;	Our data is fixed in common so nothing is needed
+;
+.macro switch
+.endm
+
+.macro switchback
+.endm
+
 sio_handler_im2	a, SIOA_C, SIOA_D, reti
 sio_handler_im2 b, SIOB_C, SIOB_D, reti
 
-- 
2.34.1