mmc: dw_mmc: Add "disable-wp" device tree property

The "disable-wp" property is used to specify that a given SD card slot
doesn't have a concept of write protect.  This eliminates the need for
special case code for SD slots that should never be write protected
(like a micro SD slot or a dev board).

The dw_mmc driver is special in needing to specify "disable-wp"
because the lack of a "wp-gpios" property means to use the special
purpose write protect line.  On some other mmc devices the lack of
"wp-gpios" means that write protect should be disabled.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Acked-by: Seungwon Jeon <tgih.jun@samsung.com>
Acked-by: Will Newton <will.newton@imgtec.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Chris Ball <cjb@laptop.org>

Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt

@@ -26,8 +26,16 @@ Required Properties:
 	* bus-width: as documented in mmc core bindings.
 
 	* wp-gpios: specifies the write protect gpio line. The format of the
-	  gpio specifier depends on the gpio controller. If the write-protect
-	  line is not available, this property is optional.
+	  gpio specifier depends on the gpio controller. If a GPIO is not used
+	  for write-protect, this property is optional.
+
+	* disable-wp: If the wp-gpios property isn't present then (by default)
+	  we'd assume that the write protect is hooked up directly to the
+	  controller's special purpose write protect line (accessible via
+	  the WRTPRT register).  However, it's possible that we simply don't
+	  want write protect.  In that case specify 'disable-wp'.
+	  NOTE: This property is not required for slots known to always
+	  connect to eMMC or SDIO cards.
 
 Optional properties:
 

drivers/mmc/host/dw_mmc.c

@@ -74,6 +74,7 @@ struct idmac_desc {
  * struct dw_mci_slot - MMC slot state
  * @mmc: The mmc_host representing this slot.
  * @host: The MMC controller this slot is using.
+ * @quirks: Slot-level quirks (DW_MCI_SLOT_QUIRK_XXX)
  * @ctype: Card type for this slot.
  * @mrq: mmc_request currently being processed or waiting to be
  *	processed, or NULL when the slot is idle.
@@ -88,6 +89,8 @@ struct dw_mci_slot {
 	struct mmc_host		*mmc;
 	struct dw_mci		*host;
 
+	int			quirks;
+
 	u32			ctype;
 
 	struct mmc_request	*mrq;
@@ -825,7 +828,13 @@ static int dw_mci_get_ro(struct mmc_host *mmc)
 	struct dw_mci_board *brd = slot->host->pdata;
 
 	/* Use platform get_ro function, else try on board write protect */
-	if (brd->quirks & DW_MCI_QUIRK_NO_WRITE_PROTECT)
+
+	/*
+	 * NOTE: DW_MCI_QUIRK_NO_WRITE_PROTECT will be removed in a future
+	 * patch in the series once reference to it is removed.
+	 */
+	if ((brd->quirks & DW_MCI_QUIRK_NO_WRITE_PROTECT) ||
+	    (slot->quirks & DW_MCI_SLOT_QUIRK_NO_WRITE_PROTECT))
 		read_only = 0;
 	else if (brd->get_ro)
 		read_only = brd->get_ro(slot->id);
@@ -1785,6 +1794,30 @@ static struct device_node *dw_mci_of_find_slot_node(struct device *dev, u8 slot)
 	return NULL;
 }
 
+static struct dw_mci_of_slot_quirks {
+	char *quirk;
+	int id;
+} of_slot_quirks[] = {
+	{
+		.quirk	= "disable-wp",
+		.id	= DW_MCI_SLOT_QUIRK_NO_WRITE_PROTECT,
+	},
+};
+
+static int dw_mci_of_get_slot_quirks(struct device *dev, u8 slot)
+{
+	struct device_node *np = dw_mci_of_find_slot_node(dev, slot);
+	int quirks = 0;
+	int idx;
+
+	/* get quirks */
+	for (idx = 0; idx < ARRAY_SIZE(of_slot_quirks); idx++)
+		if (of_get_property(np, of_slot_quirks[idx].quirk, NULL))
+			quirks |= of_slot_quirks[idx].id;
+
+	return quirks;
+}
+
 /* find out bus-width for a given slot */
 static u32 dw_mci_of_get_bus_wd(struct device *dev, u8 slot)
 {
@@ -1800,6 +1833,10 @@ static u32 dw_mci_of_get_bus_wd(struct device *dev, u8 slot)
 	return bus_wd;
 }
 #else /* CONFIG_OF */
+static int dw_mci_of_get_slot_quirks(struct device *dev, u8 slot)
+{
+	return 0;
+}
 static u32 dw_mci_of_get_bus_wd(struct device *dev, u8 slot)
 {
 	return 1;
@@ -1828,6 +1865,8 @@ static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
 	slot->host = host;
 	host->slot[id] = slot;
 
+	slot->quirks = dw_mci_of_get_slot_quirks(host->dev, slot->id);
+
 	mmc->ops = &dw_mci_ops;
 	mmc->f_min = DIV_ROUND_UP(host->bus_hz, 510);
 	mmc->f_max = host->bus_hz;

include/linux/mmc/dw_mmc.h

@@ -209,9 +209,18 @@ struct dw_mci_dma_ops {
 #define DW_MCI_QUIRK_HIGHSPEED			BIT(2)
 /* Unreliable card detection */
 #define DW_MCI_QUIRK_BROKEN_CARD_DETECTION	BIT(3)
+
 /* Write Protect detection not available */
+/*
+ * NOTE: DW_MCI_QUIRK_NO_WRITE_PROTECT will be removed in a future
+ * patch in the series once reference to it is removed.
+ */
 #define DW_MCI_QUIRK_NO_WRITE_PROTECT		BIT(4)
 
+/* Slot level quirks */
+/* This slot has no write protect */
+#define DW_MCI_SLOT_QUIRK_NO_WRITE_PROTECT	BIT(0)
+
 struct dma_pdata;
 
 struct block_settings {