[PATCH v3 1/4] mmc: dw_mmc: Add "disable-wp" device tree property

Doug Anderson
2012-11-30T05:07:27Z

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>
---
Changes in v3:
- New for this version of the patch series. Chose "disable-wp" rather
than the discussed "broken-internal-wp" since it mapped more cleanly
to an existing quirk (and the only reason to specify that the
internal wp is broken is if you're disabling the write protect
anyway).

.../devicetree/bindings/mmc/synopsis-dw-mshc.txt | 12 +++++-
drivers/mmc/host/dw_mmc.c | 36 +++++++++++++++++++-
include/linux/mmc/dw_mmc.h | 4 ++
3 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
index 06cd32d08..726fd21 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 7342029..b47b1e9 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;
@@ -828,7 +831,8 @@ 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)
+ 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);
@@ -1788,6 +1792,30 @@ 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)
{
@@ -1803,6 +1831,10 @@ 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;
@@ -1831,6 +1863,8 @@ 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 34be4f4..24dc3a8 100644
--- a/include/linux/mmc/dw_mmc.h
+++ b/include/linux/mmc/dw_mmc.h
@@ -212,6 +212,10 @@ struct dw_mci_dma_ops {
/* Write Protect detection not available */
#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 {
--
1.7.7.3