linux-kernel - Re: [PATCH] mmc : Use wait_for_completion_timeout() instead of wait_for

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Date:	Tue, 20 Sep 2011 23:22:38 +0900
From:	NamJae Jeon <linkinjeon@...il.com>
To:	Murali Krishna Palnati <palnati.muralikrishna@...il.com>
Cc:	Ulf Hansson <ulf.hansson@...ricsson.com>,
	"cjb@...top.org" <cjb@...top.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc : Use wait_for_completion_timeout() instead of
 wait_for_completion in case of write.

2011/9/20 Murali Krishna Palnati <palnati.muralikrishna@...il.com>:
> On Tue, Sep 20, 2011 at 4:05 PM, NamJae Jeon <linkinjeon@...il.com> wrote:
>> yes, I knew. But if card keep holding busy line(data 0) in the middle
>> of DMA operation(multi blocks write),  host driver layer can not know
>> card status in this situation.
>
> The host driver shall start a software timer and indpendently needs to
> watch out for the expiry of the timeout. If the host doesn't hear back
> from the
> controller/DMA engine even after waiting for the specified timeout,
> then the timer handler that gets invoked can then do the necessary
> cleanup and
> inform the MMC core layer that the request failed. Does this sound feasible?
>

It may be no good choice that sw timer is on host driver. also I don't
know what is different.
It is the same as the ata driver's dma_map_sg.
dma_map_sg is repectively called in mmc host driver. but it is being
processed in ata core of ata driver.
because it is common routine, ata core have called it instead of host driver.
if it is processed in mmc core, there is no need to modify several
hosts.(except dma controller reset)
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