linux-kernel - Re: [PATCH 1/2] mtd: rawnand: denali: remove ->dev

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Message-ID: <20180919232630.105c3373@xps13>
Date:   Wed, 19 Sep 2018 23:26:30 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-mtd@...ts.infradead.org,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        linux-kernel@...r.kernel.org, Marek Vasut <marek.vasut@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH 1/2] mtd: rawnand: denali: remove ->dev_ready() hook

Hi Masahiro,

Masahiro Yamada <yamada.masahiro@...ionext.com> wrote on Fri,  7 Sep
2018 16:28:28 +0900:

> The Denali NAND IP has no way to read out the current signal level
> of the R/B# pin.  Instead, denali_dev_ready() checks if the R/B#
> transition has already happened. (The INTR__INT_ACT interrupt is
> asserted at the rising edge of the R/B# pin.)  It is not a correct
> way to implement the ->dev_ready() hook.
> 
> In fact, it has a drawback; in the nand_scan_ident phase, the chip
> detection iterates over maxchips until it fails to find a homogeneous
> chip.  For the last loop, nand_reset() fails if no chip is there.
> 
> If ->dev_ready hook exists, nand_command(_lp) calls nand_wait_ready()
> after NAND_CMD_RESET.  However, we know denali_dev_ready() never
> returns 1 unless there exists a chip that toggles R/B# in that chip
> select.  Then, nand_wait_ready() just ends up with wasting 400 msec,
> in the end, shows the "timeout while waiting for chip to become ready"
> warning.
> 
> Let's remove the mis-implemented dev_ready hook, and fallback to
> sending the NAND_CMD_STATUS and nand_wait_status_ready(), which
> bails out more quickly.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---

Both patches applied on nand/next.

Thanks,
Miquèl