[RFC v4 23/25] m68k/mac: Use macros for RTC accesses not magic numbers

Finn Thain
2015-07-12T10:42:18Z

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Signed-off-by: Finn Thain <fthain@telegraphics.com.au>

---

This is intended to improve code style and not affect code behaviour.
I've tested this on a Quadra 650.

I don't know the meanings of the 4 undocumented write protect register
bits 0x55, so I decided against defining 4 macros for those bits.

---
arch/m68k/mac/misc.c | 59 +++++++++++++++++++++++++++++++++++----------------
1 file changed, 41 insertions(+), 18 deletions(-)

Index: linux/arch/m68k/mac/misc.c
===================================================================
--- linux.orig/arch/m68k/mac/misc.c 2015-07-12 20:25:20.000000000 +1000
+++ linux/arch/m68k/mac/misc.c 2015-07-12 20:25:22.000000000 +1000
@@ -242,6 +242,21 @@ static void via_rtc_send(__u8 data)
}

/*
+ * These values can be found in Inside Macintosh vol. III ch. 2
+ * which has a description of the RTC chip in the original Mac.
+ */
+
+#define RTC_FLG_READ BIT(7)
+#define RTC_FLG_WRITE_PROTECT BIT(7)
+#define RTC_CMD_READ(r) (RTC_FLG_READ | (r << 2))
+#define RTC_CMD_WRITE(r) (r << 2)
+#define RTC_REG_SECONDS_0 0
+#define RTC_REG_SECONDS_1 1
+#define RTC_REG_SECONDS_2 2
+#define RTC_REG_SECONDS_3 3
+#define RTC_REG_WRITE_PROTECT 13
+
+/*
* 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
@@ -250,13 +265,17 @@ static void via_rtc_send(__u8 data)
* This function disables all interrupts while running.
*/

-static void via_pram_command(int command, __u8 *data)
+static void via_rtc_command(int command, __u8 *data)
{
unsigned long flags;
int is_read;

local_irq_save(flags);

+ /* The least significant bits must be 0b01 according to Inside Mac */
+
+ command = (command & ~3) | 1;
+
/* Enable the RTC and make sure the strobe line is high */

via1[vBufB] = (via1[vBufB] | VIA1B_vRTCClk) & ~VIA1B_vRTCEnb;
@@ -264,10 +283,10 @@ static void via_pram_command(int command
if (command & 0xFF00) { /* extended (two-byte) command */
via_rtc_send((command & 0xFF00) >> 8);
via_rtc_send(command & 0xFF);
- is_read = command & 0x8000;
+ is_read = command & (RTC_FLG_READ << 8);
} else { /* one-byte command */
via_rtc_send(command);
- is_read = command & 0x80;
+ is_read = command & RTC_FLG_READ;
}
if (is_read) {
*data = via_rtc_recv();
@@ -306,10 +325,10 @@ static long via_read_time(void)
} result, last_result;
int count = 1;

- via_pram_command(0x81, &last_result.cdata[3]);
- via_pram_command(0x85, &last_result.cdata[2]);
- via_pram_command(0x89, &last_result.cdata[1]);
- via_pram_command(0x8D, &last_result.cdata[0]);
+ via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_0), &last_result.cdata[3]);
+ via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_1), &last_result.cdata[2]);
+ via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_2), &last_result.cdata[1]);
+ via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_3), &last_result.cdata[0]);

/*
* The NetBSD guys say to loop until you get the same reading
@@ -317,10 +336,14 @@ static long via_read_time(void)
*/

while (1) {
- via_pram_command(0x81, &result.cdata[3]);
- via_pram_command(0x85, &result.cdata[2]);
- via_pram_command(0x89, &result.cdata[1]);
- via_pram_command(0x8D, &result.cdata[0]);
+ via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_0),
+ &result.cdata[3]);
+ via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_1),
+ &result.cdata[2]);
+ via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_2),
+ &result.cdata[1]);
+ via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_3),
+ &result.cdata[0]);

if (result.idata == last_result.idata)
return result.idata - RTC_OFFSET;
@@ -356,18 +379,18 @@ static void via_write_time(long time)
/* Clear the write protect bit */

temp = 0x55;
- via_pram_command(0x35, &temp);
+ via_rtc_command(RTC_CMD_WRITE(RTC_REG_WRITE_PROTECT), &temp);

data.idata = time + RTC_OFFSET;
- via_pram_command(0x01, &data.cdata[3]);
- via_pram_command(0x05, &data.cdata[2]);
- via_pram_command(0x09, &data.cdata[1]);
- via_pram_command(0x0D, &data.cdata[0]);
+ via_rtc_command(RTC_CMD_WRITE(RTC_REG_SECONDS_0), &data.cdata[3]);
+ via_rtc_command(RTC_CMD_WRITE(RTC_REG_SECONDS_1), &data.cdata[2]);
+ via_rtc_command(RTC_CMD_WRITE(RTC_REG_SECONDS_2), &data.cdata[1]);
+ via_rtc_command(RTC_CMD_WRITE(RTC_REG_SECONDS_3), &data.cdata[0]);

/* Set the write protect bit */

- temp = 0xD5;
- via_pram_command(0x35, &temp);
+ temp = 0x55 | RTC_FLG_WRITE_PROTECT;
+ via_rtc_command(RTC_CMD_WRITE(RTC_REG_WRITE_PROTECT), &temp);
}

static void via_shutdown(void)