kernel: m25p80: allow fallback from spi_flash_read to regular SPI transfer

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

1 files changed, 36 insertions, 0 deletions

diff --git a/target/linux/generic/pending-4.9/450-mtd-m25p80-allow-fallback-from-spi_flash_read-to-reg.patch b/target/linux/generic/pending-4.9/450-mtd-m25p80-allow-fallback-from-spi_flash_read-to-reg.patch
new file mode 100644
index 0000000000..feaf8cb25c
--- /dev/null
+++ b/target/linux/generic/pending-4.9/450-mtd-m25p80-allow-fallback-from-spi_flash_read-to-reg.patch
@@ -0,0 +1,36 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Fri, 23 Feb 2018 17:12:16 +0100
+Subject: [PATCH] mtd: m25p80: allow fallback from spi_flash_read to regular
+ SPI transfer
+
+Some flash controllers, e.g. on the ath79 platform can support a fast
+flash read via memory mapping, but only if the flash chip is in
+3-byte address mode.
+
+Since spi_flash_read_supported does not have access to the same data as
+spi_flash_read, the driver can't detect an unsupported call until m25p80
+has decided to use spi_flash_read.
+
+Allow the driver to indicate a fallback to a regular SPI transfer by
+returning -EOPNOTSUPP
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/drivers/mtd/devices/m25p80.c
++++ b/drivers/mtd/devices/m25p80.c
+@@ -155,9 +155,11 @@ static ssize_t m25p80_read(struct spi_no
+ 		msg.data_nbits = m25p80_rx_nbits(nor);
+ 
+ 		ret = spi_flash_read(spi, &msg);
+-		if (ret < 0)
+-			return ret;
+-		return msg.retlen;
++		if (ret != -EOPNOTSUPP) {
++			if (ret < 0)
++				return ret;
++			return msg.retlen;
++		}
+ 	}
+ 
+ 	spi_message_init(&m);