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

[Liang Yang]

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?
>