From f842a40df4d26bd74b92a3903096fc6b1709222d Mon Sep 17 00:00:00 2001
From: Tim Radvan <tim@tjvr.org>
Date: Fri, 2 Apr 2021 19:35:18 +0100
Subject: [PATCH] rp2/rp2_pio: Add fifo_join support for PIO.

The PIO state machines on the RP2040 have 4 word deep TX and RX FIFOs.  If
you only need one direction, you can "merge" them into either a single 8
word deep TX or RX FIFO.

We simply add constants to the PIO object, and set the appropriate bits in
`shiftctrl`.

Resolves #6854.

Signed-off-by: Tim Radvan <tim@tjvr.org>
---
 examples/rp2/pio_uart_rx.py | 1 +
 ports/rp2/modules/rp2.py    | 6 ++++--
 ports/rp2/rp2_pio.c         | 4 ++++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/examples/rp2/pio_uart_rx.py b/examples/rp2/pio_uart_rx.py
index 41dfde3dad..080b6bd639 100644
--- a/examples/rp2/pio_uart_rx.py
+++ b/examples/rp2/pio_uart_rx.py
@@ -22,6 +22,7 @@ PIO_RX_PIN = Pin(3, Pin.IN, Pin.PULL_UP)
     autopush=True,
     push_thresh=8,
     in_shiftdir=rp2.PIO.SHIFT_RIGHT,
+    fifo_join=PIO.JOIN_RX,
 )
 def uart_rx_mini():
     # fmt: off
diff --git a/ports/rp2/modules/rp2.py b/ports/rp2/modules/rp2.py
index 17e35c73b7..c7e4d1fdd9 100644
--- a/ports/rp2/modules/rp2.py
+++ b/ports/rp2/modules/rp2.py
@@ -31,7 +31,8 @@ class PIOASMEmit:
         autopush=False,
         autopull=False,
         push_thresh=32,
-        pull_thresh=32
+        pull_thresh=32,
+        fifo_join=0
     ):
         # uarray is a built-in module so importing it here won't require
         # scanning the filesystem.
@@ -40,7 +41,8 @@ class PIOASMEmit:
         self.labels = {}
         execctrl = 0
         shiftctrl = (
-            (pull_thresh & 0x1F) << 25
+            fifo_join << 30
+            | (pull_thresh & 0x1F) << 25
             | (push_thresh & 0x1F) << 20
             | out_shiftdir << 19
             | in_shiftdir << 18
diff --git a/ports/rp2/rp2_pio.c b/ports/rp2/rp2_pio.c
index 5f93f10c26..44928c0a88 100644
--- a/ports/rp2/rp2_pio.c
+++ b/ports/rp2/rp2_pio.c
@@ -360,6 +360,10 @@ STATIC const mp_rom_map_elem_t rp2_pio_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_SHIFT_LEFT), MP_ROM_INT(0) },
     { MP_ROM_QSTR(MP_QSTR_SHIFT_RIGHT), MP_ROM_INT(1) },
 
+    { MP_ROM_QSTR(MP_QSTR_JOIN_NONE), MP_ROM_INT(0) },
+    { MP_ROM_QSTR(MP_QSTR_JOIN_TX), MP_ROM_INT(1) },
+    { MP_ROM_QSTR(MP_QSTR_JOIN_RX), MP_ROM_INT(2) },
+
     { MP_ROM_QSTR(MP_QSTR_IRQ_SM0), MP_ROM_INT(0x100) },
     { MP_ROM_QSTR(MP_QSTR_IRQ_SM1), MP_ROM_INT(0x200) },
     { MP_ROM_QSTR(MP_QSTR_IRQ_SM2), MP_ROM_INT(0x400) },