pinctrl: samsung: Add filter selection support for alive bank on gs101

Newer Exynos based SoCs have a filter selection bitfield in the filter
configuration registers on alive bank pins. This allows the selection of
a digital or analog delay filter for each pin. Add support for selecting
and enabling the filter.

On suspend we set the analog filter to all pins in the bank (as the
digital filter relies on a clock). On resume the digital filter is
reapplied to all pins in the bank. The digital filter is working via
a clock and has an adjustable filter delay flt_width bitfield, whereas
the analog filter uses a fixed delay.

The filter determines to what extent signal fluctuations received through
the pad are considered glitches.

The code path can be exercised using
echo mem > /sys/power/state
And then wake the device using a eint gpio

Reviewed-by: André Draszik <andre.draszik@linaro.org>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Link: https://lore.kernel.org/r/20250402-pinctrl-fltcon-suspend-v6-4-78ce0d4eb30c@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

drivers/pinctrl/samsung/pinctrl-exynos.c

@@ -370,6 +370,37 @@ struct exynos_eint_gpio_save {
 	u32 eint_mask;
 };
 
+static void exynos_eint_update_flt_reg(void __iomem *reg, int cnt, int con)
+{
+	unsigned int val, shift;
+	int i;
+
+	val = readl(reg);
+	for (i = 0; i < cnt; i++) {
+		shift = i * EXYNOS_FLTCON_LEN;
+		val &= ~(EXYNOS_FLTCON_DIGITAL << shift);
+		val |= con << shift;
+	}
+	writel(val, reg);
+}
+
+/*
+ * Set the desired filter (digital or analog delay) and enable it to
+ * every pin in the bank. Note the filter selection bitfield is only
+ * found on alive banks. The filter determines to what extent signal
+ * fluctuations received through the pad are considered glitches.
+ */
+static void exynos_eint_set_filter(struct samsung_pin_bank *bank, int filter)
+{
+	unsigned int off = EXYNOS_GPIO_EFLTCON_OFFSET + bank->eint_fltcon_offset;
+	void __iomem *reg = bank->drvdata->virt_base + off;
+	unsigned int con = EXYNOS_FLTCON_EN | filter;
+
+	for (int n = 0; n < bank->nr_pins; n += 4)
+		exynos_eint_update_flt_reg(reg + n,
+					   min(bank->nr_pins - n, 4), con);
+}
+
 /*
  * exynos_eint_gpio_init() - setup handling of external gpio interrupts.
  * @d: driver data of samsung pinctrl driver.
@@ -832,6 +863,7 @@ void gs101_pinctrl_suspend(struct samsung_pin_bank *bank)
 			 bank->name, save->eint_mask);
 	} else if (bank->eint_type == EINT_TYPE_WKUP) {
 		exynos_set_wakeup(bank);
+		exynos_eint_set_filter(bank, EXYNOS_FLTCON_ANALOG);
 	}
 }
 
@@ -887,6 +919,8 @@ void gs101_pinctrl_resume(struct samsung_pin_bank *bank)
 			writel(save->eint_fltcon1, eint_fltcfg0 + 4);
 		writel(save->eint_mask, regs + bank->irq_chip->eint_mask
 		       + bank->eint_offset);
+	} else if (bank->eint_type == EINT_TYPE_WKUP) {
+		exynos_eint_set_filter(bank, EXYNOS_FLTCON_DIGITAL);
 	}
 }
 

drivers/pinctrl/samsung/pinctrl-exynos.h

@@ -52,6 +52,26 @@
 #define EXYNOS_EINT_MAX_PER_BANK	8
 #define EXYNOS_EINT_NR_WKUP_EINT
 
+/*
+ * EINT filter configuration register (on alive banks) has
+ * the following layout.
+ *
+ * BitfieldName[PinNum][Bit:Bit]
+ * FLT_EN[3][31] FLT_SEL[3][30] FLT_WIDTH[3][29:24]
+ * FLT_EN[2][23] FLT_SEL[2][22] FLT_WIDTH[2][21:16]
+ * FLT_EN[1][15] FLT_SEL[1][14] FLT_WIDTH[1][13:8]
+ * FLT_EN[0][7]  FLT_SEL[0][6]  FLT_WIDTH[0][5:0]
+ *
+ * FLT_EN	0x0 = Disable, 0x1=Enable
+ * FLT_SEL	0x0 = Analog delay filter, 0x1 Digital filter (clock count)
+ * FLT_WIDTH	Filtering width. Valid when FLT_SEL is 0x1
+ */
+
+#define EXYNOS_FLTCON_EN		BIT(7)
+#define EXYNOS_FLTCON_DIGITAL		BIT(6)
+#define EXYNOS_FLTCON_ANALOG		(0 << 6)
+#define EXYNOS_FLTCON_LEN		8
+
 #define EXYNOS_PIN_BANK_EINTN(pins, reg, id)		\
 	{						\
 		.type		= &bank_type_off,	\