linux-kernel - Re: [PATCH v2 05/10] mtd: rawnand: denali: use more precise timeout for NAND_OP_WAITRDT

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Message-ID: <20190304094346.3b62e6cd@xps13>
Date:   Mon, 4 Mar 2019 09:43:46 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-mtd@...ts.infradead.org,
        Boris Brezillon <bbrezillon@...nel.org>,
        Brian Norris <computersforpeace@...il.com>,
        linux-kernel@...r.kernel.org, Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH v2 05/10] mtd: rawnand: denali: use more precise timeout
 for NAND_OP_WAITRDT_INSTR

Hi Masahiro,

Masahiro Yamada <yamada.masahiro@...ionext.com> wrote on Tue, 12 Feb
2019 16:12:57 +0900:

> Currently, wait_for_completion_timeout() is always passed in the
> hard-coded msec_to_jiffies(1000). There is no specific reason for
> 1000 msec, but it was chosen to be long enough.
> 
> With the exec_op() conversion, NAND_OP_WAITRDY_INSTR provides more
> precise timeout value, depending on the preceding command. Let's use
> it (+ 100 msec) to bail out earlier in error case. The 100 msec extra
> is in case the heavy load on the system.
> 
> I am still keeping the hard-coded values for other higher level hooks
> such as page_read, page_write, etc. We know the value of tR, tPROG, but
> we have unknowledge about the data transfer speed of the DMA engine.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>

I really am not convinced by this change. Please just define a timeout
big enough for most cases (1000 is okay) and use it systematically.

Thanks,
Miquèl