dm: blk: Improve block device claiming

The intention with block devices is that the device number (devnum field
in its descriptor) matches the alias of its parent device. For example,
with:

	aliases {
		mmc0 = "/sdhci@700b0600";
		mmc1 = "/sdhci@700b0400";
	}

we expect that the block devices for mmc0 and mmc1 would have device
numbers of 0 and 1 respectively.

Unfortunately this does not currently always happen. If there is another
MMC device earlier in the driver model data structures its block device
will be created first. It will therefore get device number 0 and mmc0
will therefore miss out. In this case the MMC device will have sequence
number 0 but its block device will not.

To avoid this, allow a device to request a device number and bump any
existing device number that is using it. This all happens during the
binding phase so it is safe to change these numbers around. This allows
device numbers to match the aliases in all circumstances.

Add a test to verify the behaviour.

Signed-off-by: Simon Glass <sjg@chromium.org>

3 files changed, 79 insertions, 6 deletions

diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 9077a82876..7dde95d4b1 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -12,6 +12,8 @@
 		eth3 = &eth_3;
 		eth5 = &eth_5;
 		i2c0 = "/i2c@0";
+		mmc0 = "/mmc0";
+		mmc1 = "/mmc1";
 		pci0 = &pci;
 		remoteproc1 = &rproc_1;
 		remoteproc2 = &rproc_2;
@@ -259,7 +261,15 @@
 		mbox-names = "other", "test";
 	};
 
-	mmc {
+	mmc2 {
+		compatible = "sandbox,mmc";
+	};
+
+	mmc1 {
+		compatible = "sandbox,mmc";
+	};
+
+	mmc0 {
 		compatible = "sandbox,mmc";
 	};
 
diff --git a/drivers/block/blk-uclass.c b/drivers/block/blk-uclass.c
index 881c39f774..6145675271 100644
--- a/drivers/block/blk-uclass.c
+++ b/drivers/block/blk-uclass.c
@@ -486,6 +486,31 @@ static int blk_next_free_devnum(enum if_type if_type)
 	return ret + 1;
 }
 
+static int blk_claim_devnum(enum if_type if_type, int devnum)
+{
+	struct udevice *dev;
+	struct uclass *uc;
+	int ret;
+
+	ret = uclass_get(UCLASS_BLK, &uc);
+	if (ret)
+		return ret;
+	uclass_foreach_dev(dev, uc) {
+		struct blk_desc *desc = dev_get_uclass_platdata(dev);
+
+		if (desc->if_type == if_type && desc->devnum == devnum) {
+			int next = blk_next_free_devnum(if_type);
+
+			if (next < 0)
+				return next;
+			desc->devnum = next;
+			return 0;
+		}
+	}
+
+	return -ENOENT;
+}
+
 int blk_create_device(struct udevice *parent, const char *drv_name,
 		      const char *name, int if_type, int devnum, int blksz,
 		      lbaint_t size, struct udevice **devp)
@@ -495,11 +520,14 @@ int blk_create_device(struct udevice *parent, const char *drv_name,
 	int ret;
 
 	if (devnum == -1) {
-		ret = blk_next_free_devnum(if_type);
-		if (ret < 0)
+		devnum = blk_next_free_devnum(if_type);
+	} else {
+		ret = blk_claim_devnum(if_type, devnum);
+		if (ret < 0 && ret != -ENOENT)
 			return ret;
-		devnum = ret;
 	}
+	if (devnum < 0)
+		return devnum;
 	ret = device_bind_driver(parent, drv_name, name, &dev);
 	if (ret)
 		return ret;
diff --git a/test/dm/blk.c b/test/dm/blk.c
index 3e34336fae..5c5eb829a0 100644
--- a/test/dm/blk.c
+++ b/test/dm/blk.c
@@ -83,12 +83,12 @@ static int dm_test_blk_usb(struct unit_test_state *uts)
 	ut_asserteq_ptr(usb_dev, dev_get_parent(dev));
 
 	/* Check we have one block device for each mass storage device */
-	ut_asserteq(4, count_blk_devices());
+	ut_asserteq(6, count_blk_devices());
 
 	/* Now go around again, making sure the old devices were unbound */
 	ut_assertok(usb_stop());
 	ut_assertok(usb_init());
-	ut_asserteq(4, count_blk_devices());
+	ut_asserteq(6, count_blk_devices());
 	ut_assertok(usb_stop());
 
 	return 0;
@@ -115,3 +115,38 @@ static int dm_test_blk_find(struct unit_test_state *uts)
 	return 0;
 }
 DM_TEST(dm_test_blk_find, DM_TESTF_SCAN_PDATA | DM_TESTF_SCAN_FDT);
+
+/* Test that block device numbering works as expected */
+static int dm_test_blk_devnum(struct unit_test_state *uts)
+{
+	struct udevice *dev, *mmc_dev, *parent;
+	int i;
+
+	/*
+	 * Probe the devices, with the first one being probed last. This is the
+	 * one with no alias / sequence numnber.
+	 */
+	ut_assertok(uclass_get_device(UCLASS_MMC, 1, &dev));
+	ut_assertok(uclass_get_device(UCLASS_MMC, 2, &dev));
+	ut_assertok(uclass_get_device(UCLASS_MMC, 0, &dev));
+	for (i = 0; i < 3; i++) {
+		struct blk_desc *desc;
+
+		/* Check that the bblock device is attached */
+		ut_assertok(uclass_get_device_by_seq(UCLASS_MMC, i, &mmc_dev));
+		ut_assertok(blk_find_device(IF_TYPE_MMC, i, &dev));
+		parent = dev_get_parent(dev);
+		ut_asserteq_ptr(parent, mmc_dev);
+		ut_asserteq(trailing_strtol(mmc_dev->name), i);
+
+		/*
+		 * Check that the block device devnum matches its parent's
+		 * sequence number
+		 */
+		desc = dev_get_uclass_platdata(dev);
+		ut_asserteq(desc->devnum, i);
+	}
+
+	return 0;
+}
+DM_TEST(dm_test_blk_devnum, DM_TESTF_SCAN_PDATA | DM_TESTF_SCAN_FDT);