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To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc:     Joshua Thompson <funaho@jurai.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        linux-m68k@lists.linux-m68k.org,
        Laurent Vivier <lvivier@redhat.com>,
        Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Message-Id: <0253194363af4426f9788796811a6a29fb87c713.1593318192.git.fthain@telegraphics.com.au>
In-Reply-To: <cover.1593318192.git.fthain@telegraphics.com.au>
References: <cover.1593318192.git.fthain@telegraphics.com.au>
From:   Finn Thain <fthain@telegraphics.com.au>
Subject: [PATCH 4/9] macintosh/via-macii: Remove read_done state
Date:   Sun, 28 Jun 2020 14:23:12 +1000
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The driver state machine may enter the 'read_done' state when leaving the
'idle' or 'reading' state. This transition is pointless, as is the extra
interrupt it requires. The interrupt is produced by the transceiver
(even when it has no data to send) because an extra EVEN/ODD toggle
was signalled by the driver. Drop the extra state to simplify the code.

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2") # v5.0+
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 drivers/macintosh/via-macii.c | 70 ++++++++++++++---------------------
 1 file changed, 28 insertions(+), 42 deletions(-)

diff --git a/drivers/macintosh/via-macii.c b/drivers/macintosh/via-macii.c
index 6a5cd7de05baf..d29c87943ca46 100644
--- a/drivers/macintosh/via-macii.c
+++ b/drivers/macintosh/via-macii.c
@@ -110,7 +110,6 @@ static enum macii_state {
 	idle,
 	sending,
 	reading,
-	read_done,
 } macii_state;
 
 static struct adb_request *current_req; /* first request struct in the queue */
@@ -411,8 +410,8 @@ static irqreturn_t macii_interrupt(int irq, void *arg)
 			reply_len = 1;
 		} else {
 			/* bus timeout */
-			macii_state = read_done;
 			reply_len = 0;
+			break;
 		}
 
 		/* set ADB state = even for first data byte */
@@ -471,20 +470,6 @@ static irqreturn_t macii_interrupt(int irq, void *arg)
 				current_req = req->next;
 				if (req->done)
 					(*req->done)(req);
-
-				if (!current_req)
-					macii_queue_poll();
-
-				if (current_req && macii_state == idle)
-					macii_start();
-
-				if (macii_state == idle) {
-					/* reset to shift in */
-					via[ACR] &= ~SR_OUT;
-					x = via[SR];
-					/* set ADB state idle - might get SRQ */
-					via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
-				}
 				break;
 			}
 		} else {
@@ -511,12 +496,28 @@ static irqreturn_t macii_interrupt(int irq, void *arg)
 			} else if (status == ST_ODD && reply_len == 2) {
 				srq_asserted = true;
 			} else {
-				macii_state = read_done;
+				macii_state = idle;
+
+				if (bus_timeout)
+					reply_len = 0;
+
+				if (reading_reply) {
+					struct adb_request *req = current_req;
+
+					req->reply_len = reply_len;
+
+					req->complete = 1;
+					current_req = req->next;
+					if (req->done)
+						(*req->done)(req);
+				} else if (reply_len && autopoll_devs) {
+					adb_input(reply_buf, reply_len, 0);
+				}
+				break;
 			}
 		}
 
-		if (macii_state == reading &&
-		    reply_len < ARRAY_SIZE(reply_buf)) {
+		if (reply_len < ARRAY_SIZE(reply_buf)) {
 			reply_ptr++;
 			*reply_ptr = x;
 			reply_len++;
@@ -526,37 +527,22 @@ static irqreturn_t macii_interrupt(int irq, void *arg)
 		via[B] ^= ST_MASK;
 		break;
 
-	case read_done:
-		x = via[SR];
-
-		if (bus_timeout)
-			reply_len = 0;
-
-		if (reading_reply) {
-			reading_reply = 0;
-			req = current_req;
-			req->reply_len = reply_len;
-			req->complete = 1;
-			current_req = req->next;
-			if (req->done)
-				(*req->done)(req);
-		} else if (reply_len && autopoll_devs)
-			adb_input(reply_buf, reply_len, 0);
-
-		macii_state = idle;
+	default:
+		break;
+	}
 
+	if (macii_state == idle) {
 		if (!current_req)
 			macii_queue_poll();
 
 		if (current_req)
 			macii_start();
 
-		if (macii_state == idle)
+		if (macii_state == idle) {
+			via[ACR] &= ~SR_OUT;
+			x = via[SR];
 			via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
-		break;
-
-	default:
-		break;
+		}
 	}
 
 	local_irq_restore(flags);
-- 
2.26.2