From b30e78bd005b6f08e15ea75517eb2e2b293c7b4a Mon Sep 17 00:00:00 2001
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Sun, 3 Jun 2018 22:39:46 +1000
Subject: Add arbitration mechanism

This will be used by the kernel GPIO driver to synchronize
with the CF when accessing GPIO shared with FSI.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 cf-code/cf-fsi-fw.S | 50 ++++++++++++++++++++++++++++++++++++++++++++------
 cf-fsi-fw.h         | 11 +++++++++--
 cf-fsi-test.c       |  2 +-
 3 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/cf-code/cf-fsi-fw.S b/cf-code/cf-fsi-fw.S
index a68ce68..533cf39 100644
--- a/cf-code/cf-fsi-fw.S
+++ b/cf-code/cf-fsi-fw.S
@@ -200,21 +200,56 @@ _start:
 	move.b	#FW_VERSION,%a1@(FW_VERS_REG)
 	move.b	#API_VERSION,%a1@(API_VERS_REG)
 
+	/* Clear arbitration register */
+	move.b	#0,%a1@(ARB_REG)
+
 	/*
 	 * Main command loop
 	 */
 main_loop:
 	lea	%a1@(TRACEBUF),%a3
 
-	/* Wait for command */
-1:	move.l	%a1@(CMD_REG),%d2
+	/* Wait arbitration request or command
+	 *
+	 * Note: This can run with interrupts enabled as a result of
+	 *       the stop op, so %d0 can be clobbered at any time.
+	 */
+1:	move.b	%a1@(ARB_REG),%d2
+	bne	arbitration_request
+	move.l	%a1@(CMD_REG),%d2
 	tst.b	%d2
-	bne	1f
+	bne	command_request
 	stop	#0x2000
 	bra	1b
 
+arbitration_request:
 	/* Mask interrupts */
-1:	move.w	#0x2007,%sr
+	move.w	#0x2007,%sr
+
+	/* Ack request */
+	move.b	#ARB_ARM_ACK,%a1@(ARB_REG)
+
+	/* Wait until it's cleared by the host */
+0:	move.b	%a1@(ARB_REG),%d1
+	bne	1f
+
+	/* Got it, re-load the GPIO caches */
+	move.l	%a5@(0),%DCLK
+	move.l	%a4@(0),%DDAT
+
+	/* Reconfigure data as output just in case ... */
+	bsr	config_gpio_out
+
+	/* Back to main loop */
+	bra	main_loop
+
+	/* Wait, we'll get an interrupt when the host clears it */
+1:	stop	#0x2000
+	bra	0b
+
+command_request:
+	/* Mask interrupts */
+	move.w	#0x2007,%sr
 
 	/* Mark ourselves as sending a command */
 	move.b	#STAT_SENDING,%a1@(STAT_REG)
@@ -443,10 +478,13 @@ config_gpio_in:
 	move.l	%d0,%a4@(4)
 	rts
 
-	/* Interrupt handler */
+	/* Interrupt handler
+	 *
+	 * Note: Must only clobber %d0
+	 */
 _int:
 	addq.l	#1,%a1@(INT_CNT)
-	moveq.l	#CVIC_SW_IRQ, %d0
+	moveq.l	#CVIC_SW_IRQ,%d0
 	move.l	%d0,%a2@(CVIC_SW_IRQ_CLR)
 	rte
 
diff --git a/cf-fsi-fw.h b/cf-fsi-fw.h
index 44bd8cc..36df3c9 100644
--- a/cf-fsi-fw.h
+++ b/cf-fsi-fw.h
@@ -2,7 +2,7 @@
 #define __CF_FSI_FW_H
 
 /*
- *  SRAM layout
+ *  SRAM layout: Main part
  */
 
 /* Command register:
@@ -74,7 +74,7 @@
 /* Misc */
 #define	INT_CNT			0x30 /* 32-bit interrupt count */
 #define	BAD_INT_VEC		0x34
-#define	TRACEBUF		0x40
+#define	TRACEBUF		0x100
 #define	  TR_CLKOSTART		0x00
 #define	  TR_OLEN		0x01/* + len */
 #define	  TR_CLKOBIT0		0x02
@@ -87,5 +87,12 @@
 #define	  TR_CLKIBIT0		0x80
 #define	  TR_CLKIBIT1		0x81
 
+/*
+ *  SRAM layout: GPIO arbitration part
+ */
+#define ARB_REG			0x40
+#define  ARB_ARM_REQ		0x01
+#define  ARB_ARM_ACK		0x02
+
 #endif /* __CF_FSI_FW_H */
 
diff --git a/cf-fsi-test.c b/cf-fsi-test.c
index 65c240c..56e8a8f 100644
--- a/cf-fsi-test.c
+++ b/cf-fsi-test.c
@@ -104,7 +104,7 @@ static inline void writeq(uint64_t val, void *addr)
 #define GPIO_AA_SRC_BIT		0x00010000
 #define GPIO_R_SRC_BIT		0x00000100
 
-#define CVIC_BASE		0x000c2000
+#define CVIC_BASE		0x000c2000	/* 1e602000 */
 #define CVIC_EN_REG		0x10
 #define CVIC_TRIG_REG		0x18
 
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