ARM: shmobile: R-Car: Improve documentation

Add more SYSC register documentation.
Use definitions instead of hardcoded numbers.
Comment important operations.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm/mach-shmobile/pm-rcar.c

@@ -15,15 +15,29 @@
 #include <asm/io.h>
 #include "pm-rcar.h"
 
-/* SYSC */
-#define SYSCSR 0x00
-#define SYSCISR 0x04
-#define SYSCISCR 0x08
+/* SYSC Common */
+#define SYSCSR			0x00	/* SYSC Status Register */
+#define SYSCISR			0x04	/* Interrupt Status Register */
+#define SYSCISCR		0x08	/* Interrupt Status Clear Register */
+#define SYSCIER			0x0c	/* Interrupt Enable Register */
+#define SYSCIMR			0x10	/* Interrupt Mask Register */
+
+/* SYSC Status Register */
+#define SYSCSR_PONENB		1	/* Ready for power resume requests */
+#define SYSCSR_POFFENB		0	/* Ready for power shutoff requests */
+
+/*
+ * Power Control Register Offsets inside the register block for each domain
+ * Note: The "CR" registers for ARM cores exist on H1 only
+ *       Use WFI to power off, CPG/APMU to resume ARM cores on R-Car Gen2
+ */
+#define PWRSR_OFFS		0x00	/* Power Status Register */
+#define PWROFFCR_OFFS		0x04	/* Power Shutoff Control Register */
+#define PWROFFSR_OFFS		0x08	/* Power Shutoff Status Register */
+#define PWRONCR_OFFS		0x0c	/* Power Resume Control Register */
+#define PWRONSR_OFFS		0x10	/* Power Resume Status Register */
+#define PWRER_OFFS		0x14	/* Power Shutoff/Resume Error */
 
-#define PWRSR_OFFS 0x00
-#define PWROFFCR_OFFS 0x04
-#define PWRONCR_OFFS 0x0c
-#define PWRER_OFFS 0x14
 
 #define SYSCSR_RETRIES		100
 #define SYSCSR_DELAY_US		1
@@ -39,6 +53,7 @@ static int rcar_sysc_pwr_on_off(struct rcar_sysc_ch *sysc_ch,
 {
 	int k;
 
+	/* Wait until SYSC is ready to accept a power request */
 	for (k = 0; k < SYSCSR_RETRIES; k++) {
 		if (ioread32(rcar_sysc_base + SYSCSR) & (1 << sr_bit))
 			break;
@@ -48,6 +63,7 @@ static int rcar_sysc_pwr_on_off(struct rcar_sysc_ch *sysc_ch,
 	if (k == SYSCSR_RETRIES)
 		return -EAGAIN;
 
+	/* Submit power shutoff or power resume request */
 	iowrite32(1 << sysc_ch->chan_bit,
 		  rcar_sysc_base + sysc_ch->chan_offs + reg_offs);
 
@@ -56,12 +72,12 @@ static int rcar_sysc_pwr_on_off(struct rcar_sysc_ch *sysc_ch,
 
 static int rcar_sysc_pwr_off(struct rcar_sysc_ch *sysc_ch)
 {
-	return rcar_sysc_pwr_on_off(sysc_ch, 0, PWROFFCR_OFFS);
+	return rcar_sysc_pwr_on_off(sysc_ch, SYSCSR_POFFENB, PWROFFCR_OFFS);
 }
 
 static int rcar_sysc_pwr_on(struct rcar_sysc_ch *sysc_ch)
 {
-	return rcar_sysc_pwr_on_off(sysc_ch, 1, PWRONCR_OFFS);
+	return rcar_sysc_pwr_on_off(sysc_ch, SYSCSR_PONENB, PWRONCR_OFFS);
 }
 
 static int rcar_sysc_update(struct rcar_sysc_ch *sysc_ch,
@@ -78,6 +94,7 @@ static int rcar_sysc_update(struct rcar_sysc_ch *sysc_ch,
 
 	iowrite32(isr_mask, rcar_sysc_base + SYSCISCR);
 
+	/* Submit power shutoff or resume request until it was accepted */
 	do {
 		ret = on_off_fn(sysc_ch);
 		if (ret)
@@ -87,6 +104,7 @@ static int rcar_sysc_update(struct rcar_sysc_ch *sysc_ch,
 				  sysc_ch->chan_offs + PWRER_OFFS);
 	} while (status & chan_mask);
 
+	/* Wait until the power shutoff or resume request has completed * */
 	for (k = 0; k < SYSCISR_RETRIES; k++) {
 		if (ioread32(rcar_sysc_base + SYSCISR) & isr_mask)
 			break;