[PATCH v2] mmc: sunxi-mmc: check ocr_avail on resource request

[Michael Wu <michael@allwinnertech.com>]

Some platforms have no regulator, discrete power devices are used instead.
However, sunxi_mmc_probe does not catch this exception when regulator is
absent in DTS. This leads to sd or eMMC init failure.

To solve this, a fixed vmmc regulator must be hooked up in DTS, like this:
reg_dummy_vmmc: dummy_vmmc {
	compatible = "regulator-fixed";
	regulator-name = "dummy-vmmc";
	regulator-min-microvolt = <3300000>;
	regulator-max-microvolt = <3300000>;
};

mmc0:mmc@4020000 {
	compatible = "allwinner,sun50i-a100-emmc";
	device_type = "mmc0";
	vmmc-supply = <&reg_dummy_vmmc>;
}

In this patch, we print an error message and abort the probe process if
the regulator is not specified in DTS.

Signed-off-by: Michael Wu <michael@allwinnertech.com>
---
 drivers/mmc/host/sunxi-mmc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
index 2702736a1c57..0da74bddaf87 100644
--- a/drivers/mmc/host/sunxi-mmc.c
+++ b/drivers/mmc/host/sunxi-mmc.c
@@ -1300,6 +1300,11 @@ static int sunxi_mmc_resource_request(struct sunxi_mmc_host *host,
 	if (ret)
 		return ret;
 
+	if (!host->mmc->ocr_avail) {
+		dev_err(&pdev->dev, "Could not get mmc regulator\n");
+		return -EINVAL;
+	}
+
 	host->reg_base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(host->reg_base))
 		return PTR_ERR(host->reg_base);
-- 
2.29.0