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

commit fd779eac2d upstream.

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: f9ce2eddf1 ("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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alexander Sverdlin 2025-08-21 14:00:57 +02:00 committed by Greg Kroah-Hartman
parent 2e2eb78906
commit 040c78723a
1 changed files with 13 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
drivers/mtd/nand/raw/atmel/nand-controller.c
View File

@ -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);