From: Felix Fietkau <nbd@nbd.name>
Date: Thu, 22 Feb 2018 11:11:57 +0100
Subject: [PATCH] mtd: spi-nor: allow NOR driver to write fewer bytes than
 requested

The write size can be constrained by the maximum message/transfer size
of the SPI controller. Only check for ret = 0 to avoid an infinite loop.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---

--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -2704,7 +2704,7 @@ static int spi_nor_write(struct mtd_info
 
 		write_enable(nor);
 		ret = spi_nor_write_data(nor, addr, page_remain, buf + i);
-		if (ret < 0)
+		if (ret <= 0)
 			goto write_err;
 		written = ret;