generic: spi-nor: rework broken-flash-reset

Instead of resetting flash to 3B address on remove hook, this
implementation only enters 4B mode when needed, which prevents more
unexpected reboot stuck. This implementation makes it only break when
a kernel panic happens during flash operation on 16M+ areas.
Also silent broken-flash-reset warning. We are not dealing with vendors
and it's unpleasant for users to see that unnecessary and long WARN_ON
print.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>

1 files changed, 167 insertions, 0 deletions

diff --git a/target/linux/generic/pending-5.4/481-mtd-spi-nor-rework-broken-flash-reset-support.patch b/target/linux/generic/pending-5.4/481-mtd-spi-nor-rework-broken-flash-reset-support.patch
new file mode 100644
index 0000000000..b2f73a5cbd
--- /dev/null
+++ b/target/linux/generic/pending-5.4/481-mtd-spi-nor-rework-broken-flash-reset-support.patch
@@ -0,0 +1,167 @@
+From ea92cbb50a78404e29de2cc3999a240615ffb1c8 Mon Sep 17 00:00:00 2001
+From: Chuanhong Guo <gch981213@gmail.com>
+Date: Mon, 6 Apr 2020 17:58:48 +0800
+Subject: [PATCH] mtd: spi-nor: rework broken-flash-reset support
+
+Instead of resetting flash to 3B address on remove hook, this
+implementation only enters 4B mode when needed, which prevents
+more unexpected reboot stuck. This implementation makes it only
+break when a kernel panic happens during flash operation on 16M+
+areas.
+*OpenWrt only*: silent broken-flash-reset warning. We are not dealing
+with vendors and it's unpleasant for users to se that unnecessary
+and long WARN_ON print.
+
+Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
+---
+ drivers/mtd/spi-nor/spi-nor.c | 52 +++++++++++++++++++++++++++++++++--
+ 1 file changed, 49 insertions(+), 3 deletions(-)
+
+--- a/drivers/mtd/spi-nor/spi-nor.c
++++ b/drivers/mtd/spi-nor/spi-nor.c
+@@ -616,6 +616,22 @@ static void spi_nor_set_4byte_opcodes(st
+ 	}
+ }
+ 
++static int spi_nor_check_set_addr_width(struct spi_nor *nor, loff_t addr)
++{
++	u8 addr_width;
++
++	if ((nor->flags & (SNOR_F_4B_OPCODES | SNOR_F_BROKEN_RESET)) !=
++	    SNOR_F_BROKEN_RESET)
++		return 0;
++
++	addr_width = addr & 0xff000000 ? 4 : 3;
++	if (nor->addr_width == addr_width)
++		return 0;
++
++	nor->addr_width = addr_width;
++	return nor->params.set_4byte(nor, addr_width == 4);
++}
++
+ static int macronix_set_4byte(struct spi_nor *nor, bool enable)
+ {
+ 	if (nor->spimem) {
+@@ -1259,6 +1275,10 @@ static int spi_nor_erase(struct mtd_info
+ 	if (ret)
+ 		return ret;
+ 
++	ret = spi_nor_check_set_addr_width(nor, instr->addr + instr->len);
++	if (ret < 0)
++		return ret;
++
+ 	/* whole-chip erase? */
+ 	if (len == mtd->size && !(nor->flags & SNOR_F_NO_OP_CHIP_ERASE)) {
+ 		unsigned long timeout;
+@@ -1315,6 +1335,7 @@ static int spi_nor_erase(struct mtd_info
+ 	write_disable(nor);
+ 
+ erase_err:
++	spi_nor_check_set_addr_width(nor, 0);
+ 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_ERASE);
+ 
+ 	return ret;
+@@ -1621,7 +1642,9 @@ static int spi_nor_lock(struct mtd_info
+ 	if (ret)
+ 		return ret;
+ 
++	spi_nor_check_set_addr_width(nor, ofs + len);
+ 	ret = nor->params.locking_ops->lock(nor, ofs, len);
++	spi_nor_check_set_addr_width(nor, 0);
+ 
+ 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_UNLOCK);
+ 	return ret;
+@@ -1636,7 +1659,9 @@ static int spi_nor_unlock(struct mtd_inf
+ 	if (ret)
+ 		return ret;
+ 
++	spi_nor_check_set_addr_width(nor, ofs + len);
+ 	ret = nor->params.locking_ops->unlock(nor, ofs, len);
++	spi_nor_check_set_addr_width(nor, 0);
+ 
+ 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_LOCK);
+ 	return ret;
+@@ -1651,7 +1676,9 @@ static int spi_nor_is_locked(struct mtd_
+ 	if (ret)
+ 		return ret;
+ 
++	spi_nor_check_set_addr_width(nor, ofs + len);
+ 	ret = nor->params.locking_ops->is_locked(nor, ofs, len);
++	spi_nor_check_set_addr_width(nor, 0);
+ 
+ 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_LOCK);
+ 	return ret;
+@@ -2557,6 +2584,10 @@ static int spi_nor_read(struct mtd_info
+ 	if (ret)
+ 		return ret;
+ 
++	ret = spi_nor_check_set_addr_width(nor, from + len);
++	if (ret < 0)
++		return ret;
++
+ 	while (len) {
+ 		loff_t addr = from;
+ 
+@@ -2580,6 +2611,7 @@ static int spi_nor_read(struct mtd_info
+ 	ret = 0;
+ 
+ read_err:
++	spi_nor_check_set_addr_width(nor, 0);
+ 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_READ);
+ 	return ret;
+ }
+@@ -2597,6 +2629,10 @@ static int sst_write(struct mtd_info *mt
+ 	if (ret)
+ 		return ret;
+ 
++	ret = spi_nor_check_set_addr_width(nor, to + len);
++	if (ret < 0)
++		return ret;
++
+ 	write_enable(nor);
+ 
+ 	nor->sst_write_second = false;
+@@ -2659,6 +2695,7 @@ static int sst_write(struct mtd_info *mt
+ 	}
+ sst_write_err:
+ 	*retlen += actual;
++	spi_nor_check_set_addr_width(nor, 0);
+ 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_WRITE);
+ 	return ret;
+ }
+@@ -2681,6 +2718,10 @@ static int spi_nor_write(struct mtd_info
+ 	if (ret)
+ 		return ret;
+ 
++	ret = spi_nor_check_set_addr_width(nor, to + len);
++	if (ret < 0)
++		return ret;
++
+ 	for (i = 0; i < len; ) {
+ 		ssize_t written;
+ 		loff_t addr = to + i;
+@@ -2720,6 +2761,7 @@ static int spi_nor_write(struct mtd_info
+ 	}
+ 
+ write_err:
++	spi_nor_check_set_addr_width(nor, 0);
+ 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_WRITE);
+ 	return ret;
+ }
+@@ -4726,9 +4768,13 @@ static int spi_nor_init(struct spi_nor *
+ 		 * reboots (e.g., crashes). Warn the user (or hopefully, system
+ 		 * designer) that this is bad.
+ 		 */
+-		WARN_ONCE(nor->flags & SNOR_F_BROKEN_RESET,
+-			  "enabling reset hack; may not recover from unexpected reboots\n");
+-		nor->params.set_4byte(nor, true);
++		if (nor->flags & SNOR_F_BROKEN_RESET) {
++			dev_warn(nor->dev,
++				"enabling reset hack; may not recover from unexpected reboots\n");
++			nor->addr_width = 3;
++		} else {
++			nor->params.set_4byte(nor, true);
++		}
+ 	}
+ 
+ 	return 0;