[source] mediatek: fix mdio schedule while atomic error

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/23317f18bd485e821ca494a61dc09044b1d0e371

commit 23317f18bd485e821ca494a61dc09044b1d0e371
Author: John Crispin <john at phrozen.org>
AuthorDate: Thu Sep 7 10:11:45 2017 +0200

    mediatek: fix mdio schedule while atomic error
    
    Signed-off-by: John Crispin <john at phrozen.org>
---
 target/linux/mediatek/patches-4.9/0062-mdio-atomic.patch | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/target/linux/mediatek/patches-4.9/0062-mdio-atomic.patch b/target/linux/mediatek/patches-4.9/0062-mdio-atomic.patch
new file mode 100644
index 0000000..040084d
--- /dev/null
+++ b/target/linux/mediatek/patches-4.9/0062-mdio-atomic.patch
@@ -0,0 +1,16 @@
+Index: linux-4.9.47/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+===================================================================
+--- linux-4.9.47.orig/drivers/net/ethernet/mediatek/mtk_eth_soc.c
++++ linux-4.9.47/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+@@ -97,7 +97,10 @@ static int mtk_mdio_busy_wait(struct mtk
+ 			return 0;
+ 		if (time_after(jiffies, t_start + PHY_IAC_TIMEOUT))
+ 			break;
+-		usleep_range(10, 20);
++		if (in_atomic())
++			udelay(10);
++		else
++			usleep_range(10, 20);
+ 	}
+ 
+ 	dev_err(eth->dev, "mdio: MDIO timeout\n");