[RFC PATCH 2/4] mtd: rawnand: gpmi: support fast edo timings for mx28

[Dario Binacchi]

In the mx28 reference manual there are examples of how to set up the
GPMI controller to support fast NAND EDO timing.

This patch has been tested on a 2048/64 byte NAND (Micron MT29F2G08ABAEAH4).
Kernel mtd tests:
 - mtd_nandbiterrs
 - mtd_nandecctest
 - mtd_oobtest
 - mtd_pagetest
 - mtd_readtest
 - mtd_speedtest
 - mtd_stresstest
 - mtd_subpagetest
 - mtd_torturetest [cycles_count = 10000000]
run without errors.

Before this patch (mode 0):
---------------------------
eraseblock write speed is 2098 KiB/s
eraseblock read speed is 2680 KiB/s
page write speed is 1689 KiB/s
page read speed is 2522 KiB/s
2 page write speed is 1899 KiB/s
2 page read speed is 2579 KiB/s
erase speed is 128000 KiB/s
2x multi-block erase speed is 73142 KiB/s
4x multi-block erase speed is 204800 KiB/s
8x multi-block erase speed is 256000 KiB/s
16x multi-block erase speed is 256000 KiB/s
32x multi-block erase speed is 256000 KiB/s
64x multi-block erase speed is 256000 KiB/s

After this patch (mode 5):
-------------------------
eraseblock write speed is 3390 KiB/s
eraseblock read speed is 5688 KiB/s
page write speed is 2680 KiB/s
page read speed is 4876 KiB/s
2 page write speed is 2909 KiB/s
2 page read speed is 5224 KiB/s
erase speed is 170666 KiB/s
2x multi-block erase speed is 204800 KiB/s
4x multi-block erase speed is 256000 KiB/s
8x multi-block erase speed is 256000 KiB/s
16x multi-block erase speed is 256000 KiB/s
32x multi-block erase speed is 256000 KiB/s
64x multi-block erase speed is 256000 KiB/s

Signed-off-by: Dario Binacchi <dario.binacchi at amarulasolutions.com>
Co-developed-by: Michael Trimarchi <michael at amarulasolutions.com>
---

 drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
index 65bcd1c548d2..fd935e893daf 100644
--- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
@@ -772,8 +772,8 @@ static int gpmi_setup_interface(struct nand_chip *chip, int chipnr,
 	if (IS_ERR(sdr))
 		return PTR_ERR(sdr);
 
-	/* Only MX6 GPMI controller can reach EDO timings */
-	if (sdr->tRC_min <= 25000 && !GPMI_IS_MX6(this))
+	/* Only MX28/MX6 GPMI controller can reach EDO timings */
+	if (sdr->tRC_min <= 25000 && !GPMI_IS_MX28(this) && !GPMI_IS_MX6(this))
 		return -ENOTSUPP;
 
 	/* Stop here if this call was just a check */
-- 
2.32.0