linux-kernel - Re: [PATCH 2/2] mmc: dw_mmc: check card present before starting request

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Message-ID: <e130d6fa-3fca-9925-603e-8f410cfb0297@rock-chips.com>
Date:	Fri, 27 May 2016 12:13:18 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Jaehoon Chung <jh80.chung@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	shawn.lin@...k-chips.com, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Doug Anderson <dianders@...omium.org>,
	linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH 2/2] mmc: dw_mmc: check card present before starting
 request

在 2016/5/27 11:46, Jaehoon Chung 写道:
> Hi Shawn,
>
> On 05/27/2016 12:02 PM, Shawn Lin wrote:
>> The main reason to add this check is to avoid unnecessary
>> mmc_request like the on-going cmd and the corresponding sbc
>> if the card is removed. Although we have already checked this in
>> dw_mci_handle_cd for runtime usage of sd card and dw_mci_init_slot
>> for noremovable devices, but there is a timing gap before it really
>> calls dw_mci_get_cd as mmc_detect_change needs some delay here.
>>
>> Another gain here is that we could save some checkings of card status
>> after sd card been removed.
>>
>> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
>> ---
>>
>>  drivers/mmc/host/dw_mmc.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index cb30e91..8eb7898 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -105,6 +105,7 @@ struct idmac_desc {
>>  static bool dw_mci_reset(struct dw_mci *host);
>>  static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset);
>>  static int dw_mci_card_busy(struct mmc_host *mmc);
>> +static int dw_mci_get_cd(struct mmc_host *mmc);
>>
>>  #if defined(CONFIG_DEBUG_FS)
>>  static int dw_mci_req_show(struct seq_file *s, void *v)
>> @@ -1255,7 +1256,7 @@ static void dw_mci_request(struct mmc_host *mmc, struct mmc_request *mrq)
>>  	 */
>>  	spin_lock_bh(&host->lock);
>>
>> -	if (!test_bit(DW_MMC_CARD_PRESENT, &slot->flags)) {
>> +	if (!dw_mci_get_cd(mmc)) {
>>  		spin_unlock_bh(&host->lock);
>>  		mrq->cmd->error = -ENOMEDIUM;
>>  		mmc_request_done(mmc, mrq);
>
> I think spin_lock/unlock_bh() should be removed at here.

yes, we should hole the lock before dw_mci_queue_request as
dw_mci_get_cd release it, in which state we do the minmum changes
for achieving what we need here.

I will fix it.

> Instead, Can it locate before calling dw_mci_queue_request()?
>
> Anyway, it looks good to me.
>
> Best Regards,
> Jaehoon Chung
>
>>
>
>
>
>


-- 
Best Regards
Shawn Lin