[ARM] 4784/1: S3C24XX: Fix GPIO restore glitches

The core resume code may have caused glitches in the GPIO when
restoring the GPIO state due to the order in which the GPIO registers
were being written.

Change the restore process take into account the state of the
GPIOs on resume and the state the system wants to restore them to.

See the code comments in the patch for more details of the process.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/plat-s3c24xx/pm.c

@@ -83,38 +83,39 @@ static struct sleep_save core_save[] = {
 	SAVE_ITEM(S3C2410_REFRESH),
 };
 
-static struct sleep_save gpio_save[] = {
-	SAVE_ITEM(S3C2410_GPACON),
-	SAVE_ITEM(S3C2410_GPADAT),
-
-	SAVE_ITEM(S3C2410_GPBCON),
-	SAVE_ITEM(S3C2410_GPBDAT),
-	SAVE_ITEM(S3C2410_GPBUP),
-
-	SAVE_ITEM(S3C2410_GPCCON),
-	SAVE_ITEM(S3C2410_GPCDAT),
-	SAVE_ITEM(S3C2410_GPCUP),
-
-	SAVE_ITEM(S3C2410_GPDCON),
-	SAVE_ITEM(S3C2410_GPDDAT),
-	SAVE_ITEM(S3C2410_GPDUP),
-
-	SAVE_ITEM(S3C2410_GPECON),
-	SAVE_ITEM(S3C2410_GPEDAT),
-	SAVE_ITEM(S3C2410_GPEUP),
-
-	SAVE_ITEM(S3C2410_GPFCON),
-	SAVE_ITEM(S3C2410_GPFDAT),
-	SAVE_ITEM(S3C2410_GPFUP),
-
-	SAVE_ITEM(S3C2410_GPGCON),
-	SAVE_ITEM(S3C2410_GPGDAT),
-	SAVE_ITEM(S3C2410_GPGUP),
-
-	SAVE_ITEM(S3C2410_GPHCON),
-	SAVE_ITEM(S3C2410_GPHDAT),
-	SAVE_ITEM(S3C2410_GPHUP),
+static struct gpio_sleep {
+	void __iomem	*base;
+	unsigned int	 gpcon;
+	unsigned int	 gpdat;
+	unsigned int	 gpup;
+} gpio_save[] = {
+	[0] = {
+		.base	= S3C2410_GPACON,
+	},
+	[1] = {
+		.base	= S3C2410_GPBCON,
+	},
+	[2] = {
+		.base	= S3C2410_GPCCON,
+	},
+	[3] = {
+		.base	= S3C2410_GPDCON,
+	},
+	[4] = {
+		.base	= S3C2410_GPECON,
+	},
+	[5] = {
+		.base	= S3C2410_GPFCON,
+	},
+	[6] = {
+		.base	= S3C2410_GPGCON,
+	},
+	[7] = {
+		.base	= S3C2410_GPHCON,
+	},
+};
 
+static struct sleep_save misc_save[] = {
 	SAVE_ITEM(S3C2410_DCLKCON),
 };
 
@@ -486,6 +487,184 @@ static void s3c2410_pm_configure_extint(void)
 	}
 }
 
+/* offsets for CON/DAT/UP registers */
+
+#define OFFS_CON	(S3C2410_GPACON - S3C2410_GPACON)
+#define OFFS_DAT	(S3C2410_GPADAT - S3C2410_GPACON)
+#define OFFS_UP		(S3C2410_GPBUP  - S3C2410_GPBCON)
+
+/* s3c2410_pm_save_gpios()
+ *
+ * Save the state of the GPIOs
+ */
+
+static void s3c2410_pm_save_gpios(void)
+{
+	struct gpio_sleep *gps = gpio_save;
+	unsigned int gpio;
+
+	for (gpio = 0; gpio < ARRAY_SIZE(gpio_save); gpio++, gps++) {
+		void __iomem *base = gps->base;
+
+		gps->gpcon = __raw_readl(base + OFFS_CON);
+		gps->gpdat = __raw_readl(base + OFFS_DAT);
+
+		if (gpio > 0)
+			gps->gpup = __raw_readl(base + OFFS_UP);
+
+	}
+}
+
+/* Test whether the given masked+shifted bits of an GPIO configuration
+ * are one of the SFN (special function) modes. */
+
+static inline int is_sfn(unsigned long con)
+{
+	return (con == 2 || con == 3);
+}
+
+/* Test if the given masked+shifted GPIO configuration is an input */
+
+static inline int is_in(unsigned long con)
+{
+	return con == 0;
+}
+
+/* Test if the given masked+shifted GPIO configuration is an output */
+
+static inline int is_out(unsigned long con)
+{
+	return con == 1;
+}
+
+/* s3c2410_pm_restore_gpio()
+ *
+ * Restore one of the GPIO banks that was saved during suspend. This is
+ * not as simple as once thought, due to the possibility of glitches
+ * from the order that the CON and DAT registers are set in.
+ *
+ * The three states the pin can be are {IN,OUT,SFN} which gives us 9
+ * combinations of changes to check. Three of these, if the pin stays
+ * in the same configuration can be discounted. This leaves us with
+ * the following:
+ *
+ * { IN => OUT }  Change DAT first
+ * { IN => SFN }  Change CON first
+ * { OUT => SFN } Change CON first, so new data will not glitch
+ * { OUT => IN }  Change CON first, so new data will not glitch
+ * { SFN => IN }  Change CON first
+ * { SFN => OUT } Change DAT first, so new data will not glitch [1]
+ *
+ * We do not currently deal with the UP registers as these control
+ * weak resistors, so a small delay in change should not need to bring
+ * these into the calculations.
+ *
+ * [1] this assumes that writing to a pin DAT whilst in SFN will set the
+ *     state for when it is next output.
+ */
+
+static void s3c2410_pm_restore_gpio(int index, struct gpio_sleep *gps)
+{
+	void __iomem *base = gps->base;
+	unsigned long gps_gpcon = gps->gpcon;
+	unsigned long gps_gpdat = gps->gpdat;
+	unsigned long old_gpcon;
+	unsigned long old_gpdat;
+	unsigned long old_gpup = 0x0;
+	unsigned long gpcon;
+	int nr;
+
+	old_gpcon = __raw_readl(base + OFFS_CON);
+	old_gpdat = __raw_readl(base + OFFS_DAT);
+
+	if (base == S3C2410_GPACON) {
+		/* GPACON only has one bit per control / data and no PULLUPs.
+		 * GPACON[x] = 0 => Output, 1 => SFN */
+
+		/* first set all SFN bits to SFN */
+
+		gpcon = old_gpcon | gps->gpcon;
+		__raw_writel(gpcon, base + OFFS_CON);
+
+		/* now set all the other bits */
+
+		__raw_writel(gps_gpdat, base + OFFS_DAT);
+		__raw_writel(gps_gpcon, base + OFFS_CON);
+	} else {
+		unsigned long old, new, mask;
+		unsigned long change_mask = 0x0;
+
+		old_gpup = __raw_readl(base + OFFS_UP);
+
+		/* Create a change_mask of all the items that need to have
+		 * their CON value changed before their DAT value, so that
+		 * we minimise the work between the two settings.
+		 */
+
+		for (nr = 0, mask = 0x03; nr < 32; nr += 2, mask <<= 2) {
+			old = (old_gpcon & mask) >> nr;
+			new = (gps_gpcon & mask) >> nr;
+
+			/* If there is no change, then skip */
+
+			if (old == new)
+				continue;
+
+			/* If both are special function, then skip */
+
+			if (is_sfn(old) && is_sfn(new))
+				continue;
+
+			/* Change is IN => OUT, do not change now */
+
+			if (is_in(old) && is_out(new))
+				continue;
+
+			/* Change is SFN => OUT, do not change now */
+
+			if (is_sfn(old) && is_out(new))
+				continue;
+
+			/* We should now be at the case of IN=>SFN,
+			 * OUT=>SFN, OUT=>IN, SFN=>IN. */
+
+			change_mask |= mask;
+		}
+
+		/* Write the new CON settings */
+
+		gpcon = old_gpcon & ~change_mask;
+		gpcon |= gps_gpcon & change_mask;
+
+		__raw_writel(gpcon, base + OFFS_CON);
+
+		/* Now change any items that require DAT,CON */
+
+		__raw_writel(gps_gpdat, base + OFFS_DAT);
+		__raw_writel(gps_gpcon, base + OFFS_CON);
+		__raw_writel(gps->gpup, base + OFFS_UP);
+	}
+
+	DBG("GPIO[%d] CON %08lx => %08lx, DAT %08lx => %08lx\n",
+	    index, old_gpcon, gps_gpcon, old_gpdat, gps_gpdat);
+}
+
+
+/** s3c2410_pm_restore_gpios()
+ *
+ * Restore the state of the GPIOs
+ */
+
+static void s3c2410_pm_restore_gpios(void)
+{
+	struct gpio_sleep *gps = gpio_save;
+	int gpio;
+
+	for (gpio = 0; gpio < ARRAY_SIZE(gpio_save); gpio++, gps++) {
+		s3c2410_pm_restore_gpio(gpio, gps);
+	}
+}
+
 void (*pm_cpu_prep)(void);
 void (*pm_cpu_sleep)(void);
 
@@ -535,7 +714,8 @@ static int s3c2410_pm_enter(suspend_state_t state)
 
 	/* save all necessary core registers not covered by the drivers */
 
-	s3c2410_pm_do_save(gpio_save, ARRAY_SIZE(gpio_save));
+	s3c2410_pm_save_gpios();
+	s3c2410_pm_do_save(misc_save, ARRAY_SIZE(misc_save));
 	s3c2410_pm_do_save(core_save, ARRAY_SIZE(core_save));
 	s3c2410_pm_do_save(uart_save, ARRAY_SIZE(uart_save));
 
@@ -585,8 +765,9 @@ static int s3c2410_pm_enter(suspend_state_t state)
 	/* restore the system state */
 
 	s3c2410_pm_do_restore_core(core_save, ARRAY_SIZE(core_save));
-	s3c2410_pm_do_restore(gpio_save, ARRAY_SIZE(gpio_save));
+	s3c2410_pm_do_restore(misc_save, ARRAY_SIZE(misc_save));
 	s3c2410_pm_do_restore(uart_save, ARRAY_SIZE(uart_save));
+	s3c2410_pm_restore_gpios();
 
 	s3c2410_pm_debug_init();