On 01/30/2017 04:44 PM, Daniel Golle wrote:
Hi Alexandru,
Hi Daniel,
On Mon, Jan 30, 2017 at 02:53:43PM -0800, Alexandru Gagniuc wrote:
This patch is designed to workaround an issue where an mt7620 will
hang after a reboot. This happens because the bootrom gets confused
when the SPI flash is left in 4-byte addressing mode. This change
makes sure that we can reboot the system under normal circumstances,
but does not protect against system crashes.
NACK. This should not be needed and also doesn't provide a reliable
method to avoid the problem you describe, please rather try
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=3274ba26f27becfc4193ec6e229288140651f240
I tried to backport this patch to 4.4, for a board with a w25q256 FLASH
chip. I am getting a ton of:
jffs2: Newly-erased block contained word 0x20031985 at offset ...
over the serial console.
In case you are aware of boards which neither implement a proper
reset of the flash chip nor use a flash chip which supports dedicated
4-byte opcodes, please let us know, in that case the fix might still
be needed and at least provide a best-effort solution (which may still
result in stuck under certain circumstances such as CPU resets
triggered by watchdogs or in any way out of the kernel's control)
So, how do we solve this situation for lede with linux-4.4 ?
Alex
Daniel
Signed-off-by: Alexandru Gagniuc <ale...@adaptrum.com>
---
...Reset-chip-to-3-byte-addressing-on-system.patch | 65 ++++++++++++++++++++++
1 file changed, 65 insertions(+)
create mode 100644
target/linux/ramips/patches-4.4/0800-mtd-m25p80-Reset-chip-to-3-byte-addressing-on-system.patch
diff --git
a/target/linux/ramips/patches-4.4/0800-mtd-m25p80-Reset-chip-to-3-byte-addressing-on-system.patch
b/target/linux/ramips/patches-4.4/0800-mtd-m25p80-Reset-chip-to-3-byte-addressing-on-system.patch
new file mode 100644
index 0000000..de4ee2c
--- /dev/null
+++
b/target/linux/ramips/patches-4.4/0800-mtd-m25p80-Reset-chip-to-3-byte-addressing-on-system.patch
@@ -0,0 +1,65 @@
+From 0f7fcc3dfc27a91e7672e9e589f3f558e8c41737 Mon Sep 17 00:00:00 2001
+From: Alexandru Gagniuc <ale...@adaptrum.com>
+Date: Mon, 30 Jan 2017 13:30:33 -0800
+Subject: [PATCH] mtd: m25p80: Reset chip to 3-byte addressing on system reboot
+
+Some SOCs can not handle 4-byte addressing in their mask ROM. On such
+devices if we leave the SPI flash in 4-byte mode, then reboot the
+system, the device will not boot.
+
+Some SoCs have a special output to reset all the on-board peripherals.
+This pin should be connected to the !RESET pin of the flash as well.
+Unfortunately, not all boards implement this. As a workaround for such
+hardware, reset the SPI flash to 3-byte addressing mode. This does not
+protect against system crashes, but it does allow the system to reboot
+in the case of a normal reboot.
+
+Cc: Paul Fertser <fercer...@gmail.com>
+Signed-off-by: Alexandru Gagniuc <ale...@adaptrum.com>
+---
+ drivers/mtd/devices/m25p80.c | 15 +++++++++++++++
+ 1 file changed, 15 insertions(+)
+
+diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
+index fe9ceb7..2151975 100644
+--- a/drivers/mtd/devices/m25p80.c
++++ b/drivers/mtd/devices/m25p80.c
+@@ -27,6 +27,9 @@
+ #include <linux/spi/flash.h>
+ #include <linux/mtd/spi-nor.h>
+
++#define OPCODE_RESET_ENABLE 0x66
++#define OPCODE_RESET 0x99
++
+ #define MAX_CMD_SIZE 6
+ struct m25p {
+ struct spi_device *spi;
+@@ -168,6 +171,17 @@ static int m25p80_erase(struct spi_nor *nor, loff_t
offset)
+ return 0;
+ }
+
++void m25p80_reboot(struct mtd_info *mtd)
++{
++ struct spi_nor *nor = container_of(mtd, struct spi_nor, mtd);
++ struct m25p *flash = nor->priv;
++
++ flash->command[0] = OPCODE_RESET_ENABLE;
++ spi_write(flash->spi, flash->command, 1);
++ flash->command[0] = OPCODE_RESET;
++ spi_write(flash->spi, flash->command, 1);
++}
++
+ /*
+ * board specific setup should have ensured the SPI clock used here
+ * matches what the READ command supports, at least until this driver
+@@ -197,6 +211,7 @@ static int m25p_probe(struct spi_device *spi)
+ nor->erase = m25p80_erase;
+ nor->write_reg = m25p80_write_reg;
+ nor->read_reg = m25p80_read_reg;
++ nor->mtd._reboot = m25p80_reboot;
+
+ nor->dev = &spi->dev;
+ nor->flash_node = spi->dev.of_node;
+--
+2.9.3
+
--
2.9.3
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