Re: [RFC PATCH v2 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller

[Liang Yang]

On 8/28/2018 9:26 PM, Boris Brezillon wrote:
> On Tue, 28 Aug 2018 21:21:48 +0800
> Liang Yang <liang.yang@xxxxxxxxxxx> wrote:
>
> > Hi Boris,
> >
> > On 8/24/2018 8:48 PM, Boris Brezillon wrote:
> > > On Wed, 22 Aug 2018 22:08:42 +0800
> > > Liang Yang <liang.yang@xxxxxxxxxxx> wrote:
> > >    
> > > > > You have to wait tWB, that's for sure.
> > > > >       
> > > > we have a maximum 32 commands fifo. when command is written into
> > > > NFC_REG_CMD, it doesn't mean that command is executing right now, maybe
> > > > it is buffering on the queue.Assume one ERASE operation, when 2nd
> > > > command(0xd0) is written into NFC_REG_CMD and then come into
> > > > NAND_OP_WAITRDY_INSTR, if I read the RB status by register, it may be
> > > > wrong because 0xd0 may not being executed. it is unusual unless
> > > > buffering two many command.
> > >
> > > You should flush the queue and wait for it to empty at the end of
> > > ->exec_op().
> > >    
> > > > so it seems that i still need to use nand_soft_waitrdy or wait cmd is
> > > > executed somewhere.
> > >
> > > Don't you have a WAIT_FOR_RB instruction? What is NFC_CMD_RB for? Also,
> > > NFC_CMD_IDLE seems to allow you to add an arbitrary delay, and that's
> > > probably what you should use for tWB.
> > >
> > > em, I can wait for RB by reading the status from register now. but when
> > calling nand_soft_waitrdy, i really met a problem. One *jiffies* is
> > about 4ms. When programming, it pass 1ms to
> > instr->ctx.waitrdy.timeout_ms and nand_soft_waitrdy will be only one
> > *jiffies* to reach timeout. And then calling nand_soft_waitrdy maybe at
> > the tail of 4ms interval, it may only wait 100us and next jiffies
> > arrive. Is it correct?
>
> Hm, no. If you initialize the time you compare to (using time_before()
> or time_after()) correctly it should not happen. Anyway, I keep thinking
> this is not how it should be done. Did you try NFC_CMD_RB? Did you ask
> HW designers what it was created for?
I am using NFC_CMD_RB and checking with irq. it is ok now.
> .