mmc: add feature of setting slot index via devicetree alias

Add feature of setting slot index via devicetree alias, to hard code the
mmc/sd root device.

The patch requires additional alias_id fix or it won't work.

Note: minor device number keep independent with this device alias.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>

drivers/mmc/core/core.c

@@ -52,6 +52,8 @@
 
 static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
 
+static int __mmc_max_reserved_idx = -1;
+
 /*
  * Enabling software CRCs on the data blocks can be a significant (30%)
  * performance cost, and for other reasons may not always be desired.
@@ -2467,10 +2469,46 @@ void mmc_unregister_pm_notifier(struct mmc_host *host)
 }
 #endif
 
+/*
+ * mmc_first_nonreserved_index() - get the first index that
+ * is not reserved
+ */
+int mmc_first_nonreserved_index(void)
+{
+	return __mmc_max_reserved_idx + 1;
+}
+EXPORT_SYMBOL(mmc_first_nonreserved_index);
+
+/*
+ * 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");
+}
+EXPORT_SYMBOL(mmc_get_reserved_index);
+
+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;

drivers/mmc/core/core.h

@@ -76,7 +76,8 @@ int mmc_detect_card_removed(struct mmc_host *host);
 int mmc_attach_mmc(struct mmc_host *host);
 int mmc_attach_sd(struct mmc_host *host);
 int mmc_attach_sdio(struct mmc_host *host);
-
+int mmc_first_nonreserved_index(void);
+int mmc_get_reserved_index(struct mmc_host *host);
 /* Module parameters */
 extern bool use_spi_crc;
 

drivers/mmc/core/host.c

@@ -401,6 +401,7 @@ EXPORT_SYMBOL(mmc_of_parse_voltage);
 struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 {
 	int err;
+	int alias_id;
 	struct mmc_host *host;
 
 	host = kzalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL);
@@ -409,8 +410,16 @@ 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;
 
-	err = ida_simple_get(&mmc_host_ida, 0, 0, GFP_KERNEL);
+	alias_id = mmc_get_reserved_index(host);
+	if (alias_id >= 0)
+		err = ida_simple_get(&mmc_host_ida, alias_id,
+				alias_id + 1, GFP_KERNEL);
+	else
+		err = ida_simple_get(&mmc_host_ida,
+					mmc_first_nonreserved_index(),
+					0, GFP_KERNEL);
 	if (err < 0) {
 		kfree(host);
 		return NULL;
@@ -420,7 +429,6 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 
 	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);

drivers/of/base.c

@@ -1981,6 +1981,37 @@ static void of_alias_add(struct alias_prop *ap, struct device_node *np,
 		 ap->alias, ap->stem, ap->id, np);
 }
 
+/*
+ * of_alias_max_index() - get the maximum index for a given alias stem
+ * @stem:   The alias stem for which the maximum index is searched for
+ *
+ * Given an alias stem (the alias without the number) this function
+ * returns the maximum number for which an alias exists.
+ *
+ * Return: The maximum existing alias index or -ENODEV if no alias
+ *         exists for this stem.
+ */
+int of_alias_max_index(const char *stem)
+{
+	struct alias_prop *app;
+	int max = -ENODEV;
+
+	mutex_lock(&of_mutex);
+
+	list_for_each_entry(app, &aliases_lookup, link) {
+		if (strcmp(app->stem, stem))
+			continue;
+		if (app->id > max)
+			max = app->id;
+	}
+
+	mutex_unlock(&of_mutex);
+
+	return max;
+}
+EXPORT_SYMBOL_GPL(of_alias_max_index);
+
+
 /**
  * of_alias_scan - Scan all properties of the 'aliases' node
  *

include/linux/of.h

@@ -391,6 +391,7 @@ extern int of_phandle_iterator_args(struct of_phandle_iterator *it,
 extern void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align));
 extern int of_alias_get_id(struct device_node *np, const char *stem);
 extern int of_alias_get_highest_id(const char *stem);
+extern int of_alias_max_index(const char *stem);
 extern int of_alias_get_alias_list(const struct of_device_id *matches,
 				   const char *stem, unsigned long *bitmap,
 				   unsigned int nbits);
@@ -911,6 +912,11 @@ static inline int of_alias_get_alias_list(const struct of_device_id *matches,
 	return -ENOSYS;
 }
 
+static inline int of_alias_max_index(const char *stem)
+{
+	return -ENODEV;
+}
+
 static inline int of_machine_is_compatible(const char *compat)
 {
 	return 0;