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

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Date:	Tue, 14 Oct 2014 09:51:26 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Alim Akhtar <alim.akhtar@...il.com>
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,

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.  :)

-Doug
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