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

[Liang Yang <liang.yang@amlogic.com>]

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@amlogic.com> 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?
>