linux-kernel - Re: [PATCH 06/11] mtd: rawnand: denali: use more precise timeout for NAND_OP_WAITRDT

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Date:   Fri, 8 Feb 2019 23:05:11 +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 06/11] mtd: rawnand: denali: use more precise timeout
 for NAND_OP_WAITRDT_INSTR

Hi Masahiro,

Masahiro Yamada <yamada.masahiro@...ionext.com> wrote on Fri,  8 Feb
2019 17:08:50 +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 I just chose it 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 to bail out earlier in error case.

I'm not sure using 10ms instead of 1000ms is relevant in the below
cases, 10ms is rather short for an IRQ, if your system is under load
you might end up with a timeout, not because the right IRQ did not
fire, but because the handler was not executed yet (it happened to me
in the marvell_nand.c driver recently).

Also, would you mind using a define instead of hardcoding '1000'?
 
> 
> 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>


Thanks,
Miquèl