m68k/mac: Fix PRAM accessors

This change “m68k/mac: Fix PRAM accessors” in Linux kernel is authored by Finn Thain <fthain [at] telegraphics.com.au> on Tue Jan 15 15:18:56 2019 +1100.

m68k/mac: Fix PRAM accessors

PMU-based m68k Macs pre-date PowerMac-style NVRAM. Use the appropriate
PMU commands. Also implement the missing XPRAM accessors for VIA-based
Macs.

Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit aefcb74.

There are 45 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 arch/m68k/mac/misc.c     | 43 +++++++++++++++++++++++++++++++++----------
 include/uapi/linux/pmu.h |  2 ++
 2 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/arch/m68k/mac/misc.c b/arch/m68k/mac/misc.c
index af000a0..d016ca2 100644
--- a/arch/m68k/mac/misc.c
+++ b/arch/m68k/mac/misc.c
@@ -66,23 +66,22 @@ static unsigned char pmu_pram_read_byte(int offset)
 {
 	struct adb_request req;
 
-	if (pmu_request(&req, NULL, 3, PMU_READ_NVRAM,
-			(offset >> 8) & 0xFF, offset & 0xFF) < 0)
+	if (pmu_request(&req, NULL, 3, PMU_READ_XPRAM,
+	                offset & 0xFF, 1) < 0)
 		return 0;
-	while (!req.complete)
-		pmu_poll();
-	return req.reply[3];
+	pmu_wait_complete(&req);
+
+	return req.reply[0];
 }
 
 static void pmu_pram_write_byte(unsigned char data, int offset)
 {
 	struct adb_request req;
 
-	if (pmu_request(&req, NULL, 4, PMU_WRITE_NVRAM,
-			(offset >> 8) & 0xFF, offset & 0xFF, data) < 0)
+	if (pmu_request(&req, NULL, 4, PMU_WRITE_XPRAM,
+	                offset & 0xFF, 1, data) < 0)
 		return;
-	while (!req.complete)
-		pmu_poll();
+	pmu_wait_complete(&req);
 }
 #endif /* CONFIG_ADB_PMU */
 
@@ -152,6 +151,16 @@ static void via_rtc_send(__u8 data)
 #define RTC_REG_WRITE_PROTECT   13
 
 /*
+ * Inside Mac has no information about two-byte RTC commands but
+ * the MAME/MESS source code has the essentials.
+ */
+
+#define RTC_REG_XPRAM           14
+#define RTC_CMD_XPRAM_READ      (RTC_CMD_READ(RTC_REG_XPRAM) << 8)
+#define RTC_CMD_XPRAM_WRITE     (RTC_CMD_WRITE(RTC_REG_XPRAM) << 8)
+#define RTC_CMD_XPRAM_ARG(a)    (((a & 0xE0) << 3) | ((a & 0x1F) << 2))
+
+/*
  * Execute a VIA PRAM/RTC command. For read commands
  * data should point to a one-byte buffer for the
  * resulting data. For write commands it should point
@@ -198,11 +207,25 @@ static void via_rtc_command(int command, __u8 *data)
 
 static unsigned char via_pram_read_byte(int offset)
 {
-	return 0;
+	unsigned char temp;
+
+	via_rtc_command(RTC_CMD_XPRAM_READ | RTC_CMD_XPRAM_ARG(offset), &temp);
+
+	return temp;
 }
 
 static void via_pram_write_byte(unsigned char data, int offset)
 {
+	unsigned char temp;
+
+	temp = 0x55;
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_WRITE_PROTECT), &temp);
+
+	temp = data;
+	via_rtc_command(RTC_CMD_XPRAM_WRITE | RTC_CMD_XPRAM_ARG(offset), &temp);
+
+	temp = 0x55 | RTC_FLG_WRITE_PROTECT;
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_WRITE_PROTECT), &temp);
 }
 
 /*
diff --git a/include/uapi/linux/pmu.h b/include/uapi/linux/pmu.h
index 97256f9..f2fc1bd 100644
--- a/include/uapi/linux/pmu.h
+++ b/include/uapi/linux/pmu.h
@@ -19,7 +19,9 @@
 #define PMU_POWER_CTRL		0x11	/* control power of some devices */
 #define PMU_ADB_CMD		0x20	/* send ADB packet */
 #define PMU_ADB_POLL_OFF	0x21	/* disable ADB auto-poll */
+#define PMU_WRITE_XPRAM		0x32	/* write eXtended Parameter RAM */
 #define PMU_WRITE_NVRAM		0x33	/* write non-volatile RAM */
+#define PMU_READ_XPRAM		0x3a	/* read eXtended Parameter RAM */
 #define PMU_READ_NVRAM		0x3b	/* read non-volatile RAM */
 #define PMU_SET_RTC		0x30	/* set real-time clock */
 #define PMU_READ_RTC		0x38	/* read real-time clock */

The commit for this change in Linux stable tree is aefcb74 (patch).

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