[PATCH v3 3/3] mtd: nand: raw: atmel: Fix pulse read timing for certain NAND flashes

[Alexander Dahl]

Hello Bala,

Am Wed, Oct 09, 2024 at 04:45:02AM +0000 schrieb Balamanikandan.Gunasundar at microchip.com:
> On 30/09/24 1:37 pm, Alexander Dahl wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > Hello,
> > 
> > Am Tue, May 28, 2024 at 12:32:44PM +0200 schrieb Alexander Dahl:
> >> Hei hei,
> >>
> >> Am Mon, Apr 15, 2024 at 09:57:55AM +0200 schrieb Alexander Dahl:
> >>>  From reading the S34ML02G1 and the SAM9X60 datasheets again, it seems
> >>> like we have to wait tREA after rising RE# before sampling the data.
> >>> Thus pulse time must be at least tREA.
> >>>
> >>> Without this fix we got PMECC errors when reading, after switching to
> >>> ONFI timing mode 3 on SAM9X60 SoC with S34ML02G1 raw NAND flash chip.
> >>>
> >>> The approach to set timings used before worked on sam9g20 and sama5d2
> >>> with the same flash (S34ML02G1), probably because those have a slower
> >>> mck clock rate and thus the resolution of the timings setup is not as
> >>> tight as with sam9x60.
> >>>
> >>> The approach to fix the issue was carried over from at91bootstrap, and
> >>> has been successfully tested in at91bootstrap, U-Boot and Linux.
> >>>
> >>> Link: https://github.com/linux4sam/at91bootstrap/issues/174
> >>> Cc: Li Bin <bin.li at microchip.com>
> >>> Signed-off-by: Alexander Dahl <ada at thorsis.com>
> >>> ---
> >>>
> >>> Notes:
> >>>      v3:
> >>>      - initial patch version (not present in v1 and v2)
> >>
> >> This patch was send as part of a series, which you wanted to have some
> >> more time to test.  Besides that, has anyone looked into this
> >> particular fix?  Maybe it can be applied separately?
> > 
> > I'd kindly ask what the status of this patch series is from U-Boot
> > NAND subsystem maintainers POV?  Could you test it?  Should I rebase
> > and resend?
> > 
> > Two of these three patches are specific to at91 family, what's the
> > opinion of at91 maintainers on this?
> > 
> > Link to the series discussion for reference:
> > 
> > https://lore.kernel.org/u-boot/20240415074547.779264-1-ada@thorsis.com/T/#u
> > 
> > Greets
> > Alex
> > 
> 
> Hi Alex,
> 
> Apologies for the delay in response. I also faced the same kind of 
> problem while testing our new sam7d65 board with MX30LF4G28AD nand 
> flash. I just had a workaround to increase the pulse time by 5 nsecs 
> just for testing. The issue has been reported to the validation team and 
> an investigation is under progress.
> 
> I would request a few more days for this patch alone.

Did the validation team come to any conclusion on this?

Greets
Alex

> 
> Thanks,
> Bala.
> 
> >>
> >> Greets
> >> Alex
> >>
> >>>
> >>>   drivers/mtd/nand/raw/atmel/nand-controller.c | 13 +++++++++----
> >>>   1 file changed, 9 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/drivers/mtd/nand/raw/atmel/nand-controller.c b/drivers/mtd/nand/raw/atmel/nand-controller.c
> >>> index bbafc88e44c..00ffeadd113 100644
> >>> --- a/drivers/mtd/nand/raw/atmel/nand-controller.c
> >>> +++ b/drivers/mtd/nand/raw/atmel/nand-controller.c
> >>> @@ -1133,7 +1133,7 @@ static int atmel_smc_nand_prepare_smcconf(struct atmel_nand *nand,
> >>>                                        const struct nand_data_interface *conf,
> >>>                                        struct atmel_smc_cs_conf *smcconf)
> >>>   {
> >>> -   u32 ncycles, totalcycles, timeps, mckperiodps;
> >>> +   u32 ncycles, totalcycles, timeps, mckperiodps, pulse;
> >>>      struct atmel_nand_controller *nc;
> >>>      int ret;
> >>>
> >>> @@ -1259,11 +1259,16 @@ static int atmel_smc_nand_prepare_smcconf(struct atmel_nand *nand,
> >>>                       ATMEL_SMC_MODE_TDFMODE_OPTIMIZED;
> >>>
> >>>      /*
> >>> -    * Read pulse timing directly matches tRP:
> >>> +    * Read pulse timing would directly match tRP,
> >>> +    * but some NAND flash chips (S34ML01G2 and W29N02KVxxAF)
> >>> +    * do not work properly in timing mode 3.
> >>> +    * The workaround is to extend the SMC NRD pulse to meet tREA
> >>> +    * timing.
> >>>       *
> >>> -    * NRD_PULSE = tRP
> >>> +    * NRD_PULSE = max(tRP, tREA)
> >>>       */
> >>> -   ncycles = DIV_ROUND_UP(conf->timings.sdr.tRP_min, mckperiodps);
> >>> +   pulse = max(conf->timings.sdr.tRP_min, conf->timings.sdr.tREA_max);
> >>> +   ncycles = DIV_ROUND_UP(pulse, mckperiodps);
> >>>      totalcycles += ncycles;
> >>>      ret = atmel_smc_cs_conf_set_pulse(smcconf, ATMEL_SMC_NRD_SHIFT,
> >>>                                        ncycles);
> >>> --
> >>> 2.39.2
> >>>
> >>
>