Allwinner: u-boot: Fix boot on at least one board

projects/Allwinner/patches/u-boot/0013-sunxi-mmc-increase-stabilization-delay-from-1ms-to-20ms.patch

@@ -0,0 +1,49 @@
+From: Da Xue <da@libre.computer>
+Date: Thu, 21 Jul 2022 18:08:21 -0400
+
+Some users experienced problems booting u-boot from SPL hanging here:
+
+Trying to boot from MMC1 or Trying to boot from MMC2
+
+This seems to occur with both MicroSD and eMMC modules on ALL-H3-CC.
+Increasing the delay after mmc reset fixes these boot problems.
+Some MicroSD cards are impacted more than others so it is possible that
+MicroSD internals need time to stabilize. Below is some failure data.
+
+sandisk ultra   64gb 9/20 with 1ms,  20/20 with 10ms
+sandisk ultra   16gb 2/20 with 1ms,  20/20 with 10ms
+sandisk extreme 16gb 6/20 with 10ms, 20/20 with 20ms
+
+A quick comparison of schematics show series resistors for ESD
+protection on the MicroSD GPIOs not present on all H3/H5 boards.
+It is not known if this is related to the issue.
+
+This patch adds a fixed 20ms delay to mmc init to mitigate the problem.
+If boot time optimization is required and the platform does not require
+the delay. The delay can be replaced with:
+
+writel(SUNXI_MMC_GCTRL_RESET, &priv->reg->gctrl);
+if (wait_for_bit_le32( &priv->reg->gctrl,
+SUNXI_MMC_GCTRL_RESET, false, 20, false)) {
+printf("%s: Timeout\n", __func__);
+return -ETIMEDOUT;
+}
+
+Signed-off-by: Da Xue <da@libre.computer>
+---
+ drivers/mmc/sunxi_mmc.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/drivers/mmc/sunxi_mmc.c b/drivers/mmc/sunxi_mmc.c
+index 1bb7b6d0e9..f7942b69ce 100644
+--- a/drivers/mmc/sunxi_mmc.c
++++ b/drivers/mmc/sunxi_mmc.c
+@@ -297,7 +297,7 @@ static int sunxi_mmc_core_init(struct mmc *mmc)
+ 
+ 	/* Reset controller */
+ 	writel(SUNXI_MMC_GCTRL_RESET, &priv->reg->gctrl);
+-	udelay(1000);
++	udelay(20000);
+ 
+ 	return 0;
+ }