mtd: rawnand: gpmi: use core timings instead of an empirical derivation

GPMI driver timings derivation looks very empirical and does not use
the known timings that the core wants to use with the NAND chip, by
using local defined constants that have no special meaning from the
outside world.

Simplify the way all of this is computed and use the NAND core's SDR
timings.

Integrity of the reads/writes has been checked with nandbiterrs, speed
improvements with flash_speed on a Freescale i.MX6 DualLite/Solo SABRE
Automotive Board. Measures are below, variations of less than 150kiB/s
between tests are common and then not significant. Speeds using mode 5
are the same, while speeds using mode 0 are quite improved (+40/50%
from non-optimal computation).

Forcing timings mode 0:

=======================

Before this patch:
------------------
eraseblock write speed is 2298 KiB/s
eraseblock read speed is 3636 KiB/s
page write speed is 2136 KiB/s
page read speed is 3316 KiB/s
2 page write speed is 2199 KiB/s
2 page read speed is 3468 KiB/s

After this patch:
-----------------
eraseblock write speed is 3232 KiB/s
eraseblock read speed is 5663 KiB/s
page write speed is 2915 KiB/s
page read speed is 4904 KiB/s
2 page write speed is 3084 KiB/s
2 page read speed is 5267 KiB/s

Forcing timings mode 5:
=======================

Before this patch:
------------------
eraseblock write speed is 4338 KiB/s
eraseblock read speed is 14883 KiB/s
page write speed is 3786 KiB/s
page read speed is 12800 KiB/s
2 page write speed is 4076 KiB/s
2 page read speed is 14065 KiB/s

After this patch:
-----------------
eraseblock write speed is 4309 KiB/s
eraseblock read speed is 14712 KiB/s
page write speed is 3764 KiB/s
page read speed is 12673 KiB/s
2 page write speed is 4076 KiB/s
2 page read speed is 14065 KiB/s

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>

1 files changed, 6 insertions, 34 deletions

diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
index e7e01934f50d..c2597c8107a0 100644
--- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
@@ -94,7 +94,7 @@ static const struct mtd_ooblayout_ops gpmi_ooblayout_ops = {
 static const struct gpmi_devdata gpmi_devdata_imx23 = {
 	.type = IS_MX23,
 	.bch_max_ecc_strength = 20,
-	.max_chain_delay = 16,
+	.max_chain_delay = 16000,
 	.clks = gpmi_clks_for_mx2x,
 	.clks_count = ARRAY_SIZE(gpmi_clks_for_mx2x),
 };
@@ -102,7 +102,7 @@ static const struct gpmi_devdata gpmi_devdata_imx23 = {
 static const struct gpmi_devdata gpmi_devdata_imx28 = {
 	.type = IS_MX28,
 	.bch_max_ecc_strength = 20,
-	.max_chain_delay = 16,
+	.max_chain_delay = 16000,
 	.clks = gpmi_clks_for_mx2x,
 	.clks_count = ARRAY_SIZE(gpmi_clks_for_mx2x),
 };
@@ -114,7 +114,7 @@ static const char * const gpmi_clks_for_mx6[] = {
 static const struct gpmi_devdata gpmi_devdata_imx6q = {
 	.type = IS_MX6Q,
 	.bch_max_ecc_strength = 40,
-	.max_chain_delay = 12,
+	.max_chain_delay = 12000,
 	.clks = gpmi_clks_for_mx6,
 	.clks_count = ARRAY_SIZE(gpmi_clks_for_mx6),
 };
@@ -122,7 +122,7 @@ static const struct gpmi_devdata gpmi_devdata_imx6q = {
 static const struct gpmi_devdata gpmi_devdata_imx6sx = {
 	.type = IS_MX6SX,
 	.bch_max_ecc_strength = 62,
-	.max_chain_delay = 12,
+	.max_chain_delay = 12000,
 	.clks = gpmi_clks_for_mx6,
 	.clks_count = ARRAY_SIZE(gpmi_clks_for_mx6),
 };
@@ -134,7 +134,7 @@ static const char * const gpmi_clks_for_mx7d[] = {
 static const struct gpmi_devdata gpmi_devdata_imx7d = {
 	.type = IS_MX7D,
 	.bch_max_ecc_strength = 62,
-	.max_chain_delay = 12,
+	.max_chain_delay = 12000,
 	.clks = gpmi_clks_for_mx7d,
 	.clks_count = ARRAY_SIZE(gpmi_clks_for_mx7d),
 };
@@ -695,34 +695,6 @@ static void release_resources(struct gpmi_nand_data *this)
 	release_dma_channels(this);
 }
 
-static int init_hardware(struct gpmi_nand_data *this)
-{
-	int ret;
-
-	/*
-	 * This structure contains the "safe" GPMI timing that should succeed
-	 * with any NAND Flash device
-	 * (although, with less-than-optimal performance).
-	 */
-	struct nand_timing  safe_timing = {
-		.data_setup_in_ns        = 80,
-		.data_hold_in_ns         = 60,
-		.address_setup_in_ns     = 25,
-		.gpmi_sample_delay_in_ns =  6,
-		.tREA_in_ns              = -1,
-		.tRLOH_in_ns             = -1,
-		.tRHOH_in_ns             = -1,
-	};
-
-	/* Initialize the hardwares. */
-	ret = gpmi_init(this);
-	if (ret)
-		return ret;
-
-	this->timing = safe_timing;
-	return 0;
-}
-
 static int read_page_prepare(struct gpmi_nand_data *this,
 			void *destination, unsigned length,
 			void *alt_virt, dma_addr_t alt_phys, unsigned alt_size,
@@ -2107,7 +2079,7 @@ static int gpmi_nand_probe(struct platform_device *pdev)
 	if (ret)
 		goto exit_acquire_resources;
 
-	ret = init_hardware(this);
+	ret = gpmi_init(this);
 	if (ret)
 		goto exit_nfc_init;