mmc: Allow setting slot index via devicetree alias

As with gpio, uart and others, allow specifying the name_idx via the
aliases-node in the devicetree.

On embedded devices, there is often a combination of removable (e.g.
SD card) and non-removable mmc devices (e.g. eMMC).
Therefore the name_idx might change depending on
- host of removable device
- removable card present or not

This makes it difficult to hard code the root device, if it is on the
non-removable device. E.g. if SD card is present eMMC will be mmcblk1,
if SD card is not present at boot, eMMC will be mmcblk0.

If the aliases-node is not found, the driver will act as before.

The original patch is from here:
https://www.mail-archive.com/linux-mmc@vger.kernel.org/msg26472.html

The patch requires additional alias_id fix or it won't work.
Because according to function definition the max_idx parameter of idx_alloc
is exclusive, so need add 1 or it will be unable to find the proper idx
within an invalid range.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Dong Aisheng <b29396@freescale.com>
(cherry picked from commit 35928d6c6a76a24a16edfa636f4c08293614a1e0)

3 files changed, 67 insertions, 3 deletions

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index c0300c492864..e1c271942e53 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -2228,7 +2228,13 @@ again:
 		return ERR_PTR(-ENOMEM);
 
 	spin_lock(&mmc_blk_lock);
-	ret = ida_get_new(&mmc_blk_ida, &devidx);
+	devidx = mmc_get_reserved_index(card->host);
+	if (devidx >= 0)
+		devidx = ida_simple_get(&mmc_blk_ida, devidx, devidx,
+					GFP_NOWAIT);
+	if (devidx < 0)
+		ret = ida_get_new_above(&mmc_blk_ida,
+					mmc_first_nonreserved_index(), &devidx);
 	spin_unlock(&mmc_blk_lock);
 
 	if (ret == -EAGAIN)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index cff5829790c9..c2302174fcba 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -16,6 +16,7 @@
 #include <linux/completion.h>
 #include <linux/device.h>
 #include <linux/delay.h>
+#include <linux/of.h>
 #include <linux/pagemap.h>
 #include <linux/err.h>
 #include <linux/leds.h>
@@ -3034,10 +3035,47 @@ void mmc_init_context_info(struct mmc_host *host)
 	init_waitqueue_head(&host->context_info.wait);
 }
 
+static int __mmc_max_reserved_idx = -1;
+
+/**
+ * mmc_first_nonreserved_index() - get the first index that is not reserved
+ */
+int mmc_first_nonreserved_index(void)
+{
+	return __mmc_max_reserved_idx + 1;
+}
+
+/**
+ * mmc_get_reserved_index() - get the index reserved for this host
+ *
+ * Return: The index reserved for this host or negative error value if
+ *         no index is reserved for this host
+ */
+int mmc_get_reserved_index(struct mmc_host *host)
+{
+	return of_alias_get_id(host->parent->of_node, "mmc");
+}
+
+static void mmc_of_reserve_idx(void)
+{
+	int max;
+
+	max = of_alias_max_index("mmc");
+	if (max < 0)
+		return;
+
+	__mmc_max_reserved_idx = max;
+
+	pr_debug("MMC: reserving %d slots for of aliases\n",
+			__mmc_max_reserved_idx + 1);
+}
+
 static int __init mmc_init(void)
 {
 	int ret;
 
+	mmc_of_reserve_idx();
+
 	ret = mmc_register_bus();
 	if (ret)
 		return ret;
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 848b3453517e..d3c149db2ce8 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -333,6 +333,8 @@ int mmc_of_parse(struct mmc_host *host)
 
 EXPORT_SYMBOL(mmc_of_parse);
 
+int mmc_max_reserved_idx(void);
+
 /**
  *	mmc_alloc_host - initialise the per-host structure.
  *	@extra: sizeof private data structure
@@ -344,6 +346,7 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 {
 	int err;
 	struct mmc_host *host;
+	int alias_id, min_idx, max_idx;
 
 	host = kzalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL);
 	if (!host)
@@ -351,6 +354,7 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 
 	/* scanning will be enabled when we're ready */
 	host->rescan_disable = 1;
+	host->parent = dev;
 
 again:
 	if (!ida_pre_get(&mmc_host_ida, GFP_KERNEL)) {
@@ -359,7 +363,24 @@ again:
 	}
 
 	spin_lock(&mmc_host_lock);
-	err = ida_get_new(&mmc_host_ida, &host->index);
+
+	alias_id = mmc_get_reserved_index(host);
+	if (alias_id >= 0) {
+		min_idx = alias_id;
+		max_idx = alias_id + 1;
+	} else {
+		min_idx = mmc_first_nonreserved_index();
+		max_idx = 0;
+	}
+
+	err = ida_get_new_above(&mmc_host_ida, min_idx, &host->index);
+	if (!err) {
+		if (host->index > max_idx) {
+			ida_remove(&mmc_host_ida, host->index);
+			err = -ENOSPC;
+		}
+	}
+
 	spin_unlock(&mmc_host_lock);
 
 	if (err == -EAGAIN) {
@@ -371,7 +392,6 @@ again:
 
 	dev_set_name(&host->class_dev, "mmc%d", host->index);
 
-	host->parent = dev;
 	host->class_dev.parent = dev;
 	host->class_dev.class = &mmc_host_class;
 	device_initialize(&host->class_dev);