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>

3 files changed, 59 insertions, 3 deletions

diff --git a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
index 06cd32d08052..726fd2122a13 100644
--- a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
+++ b/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:
 
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 323c5022c2ca..90f7d990551b 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/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;
diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
index 34be4f47293c..de61de5608c9 100644
--- a/include/linux/mmc/dw_mmc.h
+++ b/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 {