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    SubjectRe: [RFC PATCH v2 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller
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    On 8/28/2018 9:26 PM, Boris Brezillon wrote:
    > On Tue, 28 Aug 2018 21:21:48 +0800
    > Liang Yang <liang.yang@amlogic.com> 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@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?
    >
    > 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.
    > .
    >

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