From fcc8341738b5e544c004f3644ad578f983b507b3 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@linux.intel.com>
Date: Sun, 15 Mar 2015 16:09:34 +0000
Subject: [PATCH] socz80: poll the ethernet kernel side

We don't want to wake/execute user code with context switches each time.

TODO: Add a sensible ethernet controller wrapper in VHDL so that it looks
like a DMA ethernet controller
---
 Kernel/platform-socz80/deveth.h   |  2 ++
 Kernel/platform-socz80/ethernet.c | 39 ++++++++++++++++++++++++++++---
 Kernel/platform-socz80/main.c     |  5 +++-
 3 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/Kernel/platform-socz80/deveth.h b/Kernel/platform-socz80/deveth.h
index 36a43610..3d55122d 100644
--- a/Kernel/platform-socz80/deveth.h
+++ b/Kernel/platform-socz80/deveth.h
@@ -9,4 +9,6 @@ extern int eth_ioctl(uint8_t minor, uarg_t arg, char *data);
 
 extern void deveth_init(void);
 
+extern void eth_poll(void);
+
 #endif
\ No newline at end of file
diff --git a/Kernel/platform-socz80/ethernet.c b/Kernel/platform-socz80/ethernet.c
index 48fe291a..58d89f84 100644
--- a/Kernel/platform-socz80/ethernet.c
+++ b/Kernel/platform-socz80/ethernet.c
@@ -25,6 +25,8 @@ __sfr __at 0x3e eth_spimode;
 
 static int eth_present;
 
+static uint8_t ewait, enowait;
+
 /* In bank 0 */
 #define ERDPTL		0x00
 #define ERDPTH		0x01
@@ -234,6 +236,10 @@ static void ethernet_reset(void)
  *	Wait until free and then send a packet. We don't have an interrupt
  *	mechanism for the SPI ethernet on the SocZ80 although we could add
  *	one via a GPIO if it turns out useful
+ *
+ *	Caution: We could have two threads of execution doing a read and
+ *	a write. We won't pre-empt mid write but we may have a read poll
+ *	running, so we must shut that off
  */
 int eth_write(uint8_t minor, uint8_t rawflag, uint8_t flag)
 {
@@ -248,6 +254,10 @@ int eth_write(uint8_t minor, uint8_t rawflag, uint8_t flag)
 		udata.u_error = EFBIG;
 		return -1;
 	}
+
+	/* Stop any read polling */
+	enowait++;
+
 	eth_bank(0);
 	while (eth_get(ECON1) & 0x8) {
 		/* Not ready */
@@ -277,6 +287,10 @@ int eth_write(uint8_t minor, uint8_t rawflag, uint8_t flag)
 	 *    Start transmit
 	 */
 	eth_cmd(BFS | ECON1, 0x08);
+
+	/* Permit read polling to resume if active */
+	enowait--;
+
 	return len;
 }
 
@@ -315,11 +329,20 @@ int eth_read(uint8_t minor, uint8_t rawflag, uint8_t flag)
 
 	/* Check carrier ?? */
 
+	/* Wait for packet: bank must always be 1 before we set ewait */
 	eth_bank(1);
 
-	/* We have no IRQ so no sane blocking model .. yet */
-	if (!eth_get(EPKTCNT))	/* Any packets waiting ? */
-		return -EAGAIN;
+	/* We have no IRQ so its polled */
+	while (eth_get(EPKTCNT) == 0) {
+		ewait = 1;
+		/* We will task switch to something else or idle and
+		   in doing so enable interrupts for other tasks */
+		if (psleep_flags(&eth_present, flag))
+			return -1;
+	}
+	/* Ensure ewait is clear before we re-enable interrupts */
+	ewait = 0;
+
 	eth_bank(0);
 	eth_cmd16(WCR | ERDPTL, eth_rxnext);
 	eth_readpkt((uint8_t *)&eth, 6);
@@ -336,6 +359,16 @@ int eth_read(uint8_t minor, uint8_t rawflag, uint8_t flag)
 	return r;
 }
 
+void eth_poll(void)
+{
+	if (!ewait || enowait)
+		return;
+	/* if we are waiting for ethernet we are in bank 1, see
+	   eth_read */
+	if (eth_get(EPKTCNT))
+		wakeup(&eth_present);
+}
+
 int eth_open(uint8_t minor, uint16_t flag)
 {
 	used(flag);
diff --git a/Kernel/platform-socz80/main.c b/Kernel/platform-socz80/main.c
index 74397883..2c3138a1 100644
--- a/Kernel/platform-socz80/main.c
+++ b/Kernel/platform-socz80/main.c
@@ -3,6 +3,7 @@
 #include <kdata.h>
 #include <tty.h>
 #include <printf.h>
+#include <deveth.h>
 
 uint16_t ramtop = PROGTOP;
 
@@ -45,8 +46,10 @@ void platform_interrupt(void)
         if (st1 & 0x40)		/* TX idle */
             tty_outproc(2);
     }
-    if (ts & 1)
+    if (ts & 1) {
+        eth_poll();
         timer_interrupt();
+    }
 }
 
 void pagemap_init(void)
-- 
2.34.1