linux-kernel - Re: [PATCH] mmc: dw_mmc: Reset DMA before enabling IDMAC

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Date:	Wed, 15 Oct 2014 01:28:01 +0530
From:	Alim Akhtar <alim.akhtar@...il.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Eddie Cai(蔡枫) <eddie.cai@...k-chips.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Sonny Rao <sonnyrao@...omium.org>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Addy Ke <addy.ke@...k-chips.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] mmc: dw_mmc: Reset DMA before enabling IDMAC

Hi Doug,

On Tue, Oct 14, 2014 at 10:21 PM, Doug Anderson <dianders@...omium.org> wrote:
> Hi,
>
> On Thu, Oct 9, 2014 at 5:36 PM, Doug Anderson <dianders@...omium.org> wrote:
>> Alim,
>>
>> On Thu, Oct 9, 2014 at 3:19 PM, Alim Akhtar <alim.akhtar@...il.com> wrote:
>>> Thats fine, I think every vendor (most of them) has a custom
>>> implementation of dw_mmc, but they do have VERID register to check the
>>> dw_mmc version.
>>> The reason why I asked is, I have seen inconsistency in card
>>> enumeration on few controller version, and this patch alone does not
>>> help, and adding a call to dw_mci_idmac_reset() after DMA reset is
>>> needed. And this is what is recommended in the synopsys's data book
>>> also.
>>> Do you see any issue/side effect after adding dw_mci_idmac_reset()?
>>
>> A quick test shows no problem with adding this to Sonny's patch:
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index 66dc8fe..588b5b8 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -481,6 +481,7 @@ static void dw_mci_idmac_start_dma(struct dw_mci
>> *host, unsigned int sg_len)
>>
>>         /* Make sure to reset DMA in case we did PIO before this */
>>         dw_mci_ctrl_reset(host, SDMMC_CTRL_DMA_RESET);
>> +       dw_mci_idmac_reset(host);
>>
>>         /* Select IDMAC interface */
>>         temp = mci_readl(host, CTRL);
>>
>> I'll start reboot tests now to see how it behaves...  I think Sonny is
>> out of the office for a few days so we might need to wait for a spin,
>> but I'll run with that change in the meantime and see how it behaves
>> for me.
>>
>> Thanks!
>
> Just FYI that I've been running with Alim's proposed change for
> several days and it seems solid.  I think Sonny may be able to spin
> his patch this week.  :)
>
Sounds great. Thanks for testing.
> -Doug



-- 
Regards,
Alim
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