[PATCH] mtd: cfi_cmdset_0002: fix Cypress S29GL flash erase suspend

[Chen Bin <chenbin5635@163.com>]

On UBIFS, Cypress S29GL01GT flash is failed to access occasionally
, and throw below error information and call trace:
MTD get_chip(): chip not ready after erase suspend
UBI error: ubi_io_write: error -5 while writing 512 bytes to
PEB 932:36992, written 0 bytes
Call Trace: [jiffies: 0x10000ad9b]
[<ffffffffc0be76cc>] dump_stack+0x8/0x34
[<ffffffffc0a0b624>] ubi_io_write+0x52c/0x670
[<ffffffffc0a079e8>] ubi_eba_write_leb+0xd8/0x758
[<ffffffffc0897470>] ubifs_leb_write+0xd0/0x178
[<ffffffffc0898cd0>] ubifs_wbuf_write_nolock+0x430/0x798
[<ffffffffc088b16c>] ubifs_jnl_write_data+0x1e4/0x348
[<ffffffffc088e5a8>] do_writepage+0xc8/0x258
[<ffffffffc0714d70>] __writepage+0x18/0x78
[<ffffffffc0715ab8>] write_cache_pages+0x1e0/0x4c8
[<ffffffffc0715de0>] generic_writepages+0x40/0x78
[<ffffffffc0784620>] __writeback_single_inode+0x58/0x370
[<ffffffffc0785b84>] writeback_sb_inodes+0x2e4/0x498
[<ffffffffc0785df8>] __writeback_inodes_wb+0xc0/0x118
[<ffffffffc07862fc>] wb_writeback+0x234/0x3c0
[<ffffffffc0786918>] wb_do_writeback+0x230/0x2b0
[<ffffffffc0786a1c>] bdi_writeback_workfn+0x84/0x268
[<ffffffffc0670300>] process_one_work+0x180/0x4d0
[<ffffffffc0671848>] worker_thread+0x158/0x420
[<ffffffffc06786c0>] kthread+0xa8/0xb0
[<ffffffffc06204c8>] ret_from_kernel_thread+0x10/0x18

After issue erase suspend command, flash don't go to ready state,
and fail to access consequently.
In Cypress S29GL01GT/S29GL512T flash datasheet, the type value of
Erase Resume to next Erase suspend(tERS) is 100 µs.
If Erase Suspend followed Erase Resume without enough delay time,
Erase Suspend would fail to work.
500 μs is chosen because it works well and the latency is acceptable.

Signed-off-by: Chen Bin <chenbin5635@163.com>
---
 drivers/mtd/chips/cfi_cmdset_0002.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
index 56aa6b7..c7d18ec 100644
--- a/drivers/mtd/chips/cfi_cmdset_0002.c
+++ b/drivers/mtd/chips/cfi_cmdset_0002.c
@@ -513,6 +513,22 @@ static void cfi_fixup_m29ew_delay_after_resume(struct cfi_private *cfi)
 		cfi_udelay(500);
 }
 
+static void cfi_fixup_delay_after_resume(struct cfi_private *cfi)
+{
+	cfi_fixup_m29ew_delay_after_resume(cfi);
+
+	/*
+	 * For Cypress S29GL01GT/S29GL512T flash, the type value of
+	 * Erase Resume to next Erase suspend(tERS) is 100 µs.
+	 * If Erase Suspend followed Erase Resume without enough delay time,
+	 * Erase Suspend would fail to work.
+	 * 500 μs is chosen because it works well and the latency
+	 * is acceptable.
+	 */
+	if (cfi->mfr == CFI_MFR_AMD && (cfi->id == 0x2801 || cfi->id == 0x2301))
+		cfi_udelay(500);
+}
+
 struct mtd_info *cfi_cmdset_0002(struct map_info *map, int primary)
 {
 	struct cfi_private *cfi = map->fldrv_priv;
@@ -890,7 +906,7 @@ static void put_chip(struct map_info *map, struct flchip *chip, unsigned long ad
 		cfi_fixup_m29ew_erase_suspend(map,
 			chip->in_progress_block_addr);
 		map_write(map, cfi->sector_erase_cmd, chip->in_progress_block_addr);
-		cfi_fixup_m29ew_delay_after_resume(cfi);
+		cfi_fixup_delay_after_resume(cfi);
 		chip->oldstate = FL_READY;
 		chip->state = FL_ERASING;
 		break;
-- 
2.7.4