Messages in this thread | | | Date | Tue, 26 Sep 2017 10:23:44 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH] mtd: nand: wait for tWHR after NAND_CMD_STATUS / NAND_CMD_READID |
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On Tue, 26 Sep 2017 17:17:49 +0900 Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
> 2017-09-26 15:43 GMT+09:00 Boris Brezillon <boris.brezillon@free-electrons.com>: > > On Tue, 26 Sep 2017 12:39:24 +0900 > > Masahiro Yamada <yamada.masahiro@socionext.com> wrote: > > > >> Read Status and Read ID require tWHR before reading the first data. > >> Insert a very short wait to make sure to meet the spec. > >> > >> I have not seen any problem report for now, but nand_command() and > >> nand_command_lP() are generic hooks, so it makes sense to implement > >> fail-safe code here. > >> > >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > >> --- > > > > > OK, will do. > > > > BTW, I see unconditional wait for tWB a few lines below, > but it gives no performance regression because we will wait > much longer in nand_wait_ready().
Yep, but this one is here for quite some time. Normally there should be no problem with your ndelay(200), but I don't want to take the risk and have someone complain that his NAND controller driver is broken because of this extra delay ;-).
> > > /* > * Apply this short delay always to ensure that we do wait tWB in > * any case on any machine. > */ > ndelay(100); > > nand_wait_ready(mtd); > > > >
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