On Tue, 26 Sep 2017 12:39:24 +0900 Masahiro Yamada <yamada.masah...@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.masah...@socionext.com> > --- > > drivers/mtd/nand/nand_base.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c > index b1cf32c..55c0ba5 100644 > --- a/drivers/mtd/nand/nand_base.c > +++ b/drivers/mtd/nand/nand_base.c > @@ -742,9 +742,12 @@ static void nand_command(struct mtd_info *mtd, unsigned > int command, > case NAND_CMD_ERASE1: > case NAND_CMD_ERASE2: > case NAND_CMD_SEQIN: > + case NAND_CMD_SET_FEATURES: > + return; > + > case NAND_CMD_STATUS: > case NAND_CMD_READID: > - case NAND_CMD_SET_FEATURES: > + ndelay(200); /* tWHR */ > return; > > case NAND_CMD_RESET: > @@ -871,9 +874,12 @@ static void nand_command_lp(struct mtd_info *mtd, > unsigned int command, > case NAND_CMD_ERASE1: > case NAND_CMD_ERASE2: > case NAND_CMD_SEQIN: > + case NAND_CMD_SET_FEATURES: > + return; > + > case NAND_CMD_STATUS: > case NAND_CMD_READID: > - case NAND_CMD_SET_FEATURES: > + ndelay(200); /* tWHR */ Can you do something like nand_ccs_delay() [1] instead of unconditionally adding this 200ns delay here? I'm not worried about the overhead introduced by this ndelay(), but I don't want to risk introducing a regression. > return; > > case NAND_CMD_RNDIN: [1]http://elixir.free-electrons.com/linux/v4.14-rc2/source/drivers/mtd/nand/nand_base.c#L793