mtd: nand: raw: atmel: Respect tAR, tCLR in read setup timing

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.

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>

diff --git a/drivers/mtd/nand/raw/atmel/nand-controller.c b/drivers/mtd/nand/raw/atmel/nand-controller.c
index 84ab4a83cbd68606c4c96641e24952278b1a3a59..db94d14a3807f5090a9959a5ab4a397f3bf47815 100644 (file)
--- 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);