mmc: core: Add tunable delay before detecting card after card is inserted

Allow to use tunable delay before detecting card after card is inserted,
which either comes from firmware node, or comes from debounce value
passed on to mmc_gpiod_request_cd(). If the platform doesn't support
debounce, then we fall back to use the debounce period as the delay,
otherwise, it behaves the same as before that a HW debounce(if set) plus
a 200ms hardcode delay before detecting the card.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/host.c

@@ -179,7 +179,7 @@ static void mmc_retune_timer(struct timer_list *t)
 int mmc_of_parse(struct mmc_host *host)
 {
 	struct device *dev = host->parent;
-	u32 bus_width, drv_type;
+	u32 bus_width, drv_type, cd_debounce_delay_ms;
 	int ret;
 	bool cd_cap_invert, cd_gpio_invert = false;
 	bool ro_cap_invert, ro_gpio_invert = false;
@@ -230,11 +230,16 @@ int mmc_of_parse(struct mmc_host *host)
 	} else {
 		cd_cap_invert = device_property_read_bool(dev, "cd-inverted");
 
+		if (device_property_read_u32(dev, "cd-debounce-delay-ms",
+					     &cd_debounce_delay_ms))
+			cd_debounce_delay_ms = 200;
+
 		if (device_property_read_bool(dev, "broken-cd"))
 			host->caps |= MMC_CAP_NEEDS_POLL;
 
 		ret = mmc_gpiod_request_cd(host, "cd", 0, true,
-					   0, &cd_gpio_invert);
+					   cd_debounce_delay_ms,
+					   &cd_gpio_invert);
 		if (!ret)
 			dev_info(host->parent, "Got CD GPIO\n");
 		else if (ret != -ENOENT && ret != -ENOSYS)

drivers/mmc/core/slot-gpio.c

@@ -28,15 +28,17 @@ struct mmc_gpio {
 	irqreturn_t (*cd_gpio_isr)(int irq, void *dev_id);
 	char *ro_label;
 	char cd_label[0];
+	u32 cd_debounce_delay_ms;
 };
 
 static irqreturn_t mmc_gpio_cd_irqt(int irq, void *dev_id)
 {
 	/* Schedule a card detection after a debounce timeout */
 	struct mmc_host *host = dev_id;
+	struct mmc_gpio *ctx = host->slot.handler_priv;
 
 	host->trigger_card_event = true;
-	mmc_detect_change(host, msecs_to_jiffies(200));
+	mmc_detect_change(host, msecs_to_jiffies(ctx->cd_debounce_delay_ms));
 
 	return IRQ_HANDLED;
 }
@@ -49,6 +51,7 @@ int mmc_gpio_alloc(struct mmc_host *host)
 
 	if (ctx) {
 		ctx->ro_label = ctx->cd_label + len;
+		ctx->cd_debounce_delay_ms = 200;
 		snprintf(ctx->cd_label, len, "%s cd", dev_name(host->parent));
 		snprintf(ctx->ro_label, len, "%s ro", dev_name(host->parent));
 		host->slot.handler_priv = ctx;
@@ -261,7 +264,7 @@ int mmc_gpiod_request_cd(struct mmc_host *host, const char *con_id,
 	if (debounce) {
 		ret = gpiod_set_debounce(desc, debounce);
 		if (ret < 0)
-			return ret;
+			ctx->cd_debounce_delay_ms = debounce;
 	}
 
 	if (gpio_invert)