[PATCH 6.6.y 2/2] mtd: nand: raw: atmel: Respect tAR, tCLR in read setup timing

[Sasha Levin <sashal@kernel.org>]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

[ Upstream commit fd779eac2d659668be4d3dbdac0710afd5d6db12 ]

Having setup time 0 violates tAR, tCLR of some chips, for instance
TOSHIBA TC58NVG2S3ETAI0 cannot be detected successfully (first ID byte
being read duplicated, i.e. 98 98 dc 90 15 76 14 03 instead of
98 dc 90 15 76 ...).

Atmel Application Notes postulated 1 cycle NRD_SETUP without explanation
[1], but it looks more appropriate to just calculate setup time properly.

[1] Link: https://ww1.microchip.com/downloads/aemDocuments/documents/MPU32/ApplicationNotes/ApplicationNotes/doc6255.pdf

Cc: stable@vger.kernel.org
Fixes: f9ce2eddf176 ("mtd: nand: atmel: Add ->setup_data_interface() hooks")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Tested-by: Alexander Dahl <ada@thorsis.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/mtd/nand/raw/atmel/nand-controller.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/raw/atmel/nand-controller.c b/drivers/mtd/nand/raw/atmel/nand-controller.c
index 6e4a0c6c7cb4d..c5aff27ec4a89 100644
--- a/drivers/mtd/nand/raw/atmel/nand-controller.c
+++ b/drivers/mtd/nand/raw/atmel/nand-controller.c
@@ -1377,14 +1377,24 @@ static int atmel_smc_nand_prepare_smcconf(struct atmel_nand *nand,
 	if (ret)
 		return ret;
 
+	/*
+	 * Read setup timing depends on the operation done on the NAND:
+	 *
+	 * NRD_SETUP = max(tAR, tCLR)
+	 */
+	timeps = max(conf->timings.sdr.tAR_min, conf->timings.sdr.tCLR_min);
+	ncycles = DIV_ROUND_UP(timeps, mckperiodps);
+	totalcycles += ncycles;
+	ret = atmel_smc_cs_conf_set_setup(smcconf, ATMEL_SMC_NRD_SHIFT, ncycles);
+	if (ret)
+		return ret;
+
 	/*
 	 * The read cycle timing is directly matching tRC, but is also
 	 * dependent on the setup and hold timings we calculated earlier,
 	 * which gives:
 	 *
-	 * NRD_CYCLE = max(tRC, NRD_PULSE + NRD_HOLD)
-	 *
-	 * NRD_SETUP is always 0.
+	 * NRD_CYCLE = max(tRC, NRD_SETUP + NRD_PULSE + NRD_HOLD)
 	 */
 	ncycles = DIV_ROUND_UP(conf->timings.sdr.tRC_min, mckperiodps);
 	ncycles = max(totalcycles, ncycles);
-- 
2.51.0