linux-kernel - Re: [PATCH 4/7] mmc: dw_mmc: add samsung exynos5250 specific extentions

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Message-ID: <CAJuYYwS=qExrAjG1kgd=tPYL0pQeP+7xE1SuMaP+do-Eg3D7eQ@mail.gmail.com>
Date:	Thu, 10 May 2012 16:25:15 +0530
From:	Thomas Abraham <thomas.abraham@...aro.org>
To:	Jaehoon Chung <jh80.chung@...sung.com>
Cc:	Kyungmin Park <kmpark@...radead.org>, linux-mmc@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	linux-samsung-soc@...r.kernel.org, patches@...aro.org,
	linux-kernel@...r.kernel.org, rob.herring@...xeda.com,
	grant.likely@...retlab.ca, kgene.kim@...sung.com, cjb@...top.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/7] mmc: dw_mmc: add samsung exynos5250 specific extentions

On 2 May 2012 13:19, Jaehoon Chung <jh80.chung@...sung.com> wrote:
> On 05/02/2012 04:01 PM, Kyungmin Park wrote:
>
>> Hi,
>>
>> On 5/2/12, Thomas Abraham <thomas.abraham@...aro.org> wrote:
>>> The instantiation of the Synopsis Designware controller on Exynos5250
>>> include extension for SDR and DDR specific tx/rx phase shift timing
>>> and CIU internal divider. In addition to that, the option to skip the
>>> command hold stage is also introduced. Add support for these Exynos5250
>>> specfic extenstions.

[...]

>>> @@ -265,6 +266,10 @@ static u32 dw_mci_prepare_command(struct mmc_host *mmc,
>>> struct mmc_command *cmd)
>>>                      cmdr |= SDMMC_CMD_DAT_WR;
>>>      }
>>>
>>> +    if (slot->host->drv_data->ctrl_type == DW_MCI_TYPE_EXYNOS5250)
>>> +            if (SDMMC_CLKSEL_GET_SELCLK_DRV(mci_readl(slot->host, CLKSEL)))
>>> +                    cmdr |= SDMMC_USE_HOLD_REG;
>> Some other board, custom SOC also can use this HOLD register. So it's
>> not EXYNOS5250 specific one. I think we introduce the more generic
>> quirks for this instead of SOC specific.
>
> One more, I think that also need to check the IMPLEMENT_HOLD_REG bit in HCON register.
> It has dependency with that.

The above code is specific to Exynos5250 and hence it is not required
to check the IMPLEMENT_HOLD_REG bit in HCON register. On Exynos5250,
the hold register is implemented and available.


> As Mr.Park is mentioned, this register is clock phasing.
> In spec, card is enumerated in SDR12 or SDR25 mode, the application must program the use_hold_reg.

Exynos5250 hardware manual specifies additional restrictions on the
use of hold register. The above code checks for those restrictions and
programs the USE_HOLD_REG accordingly. Please let me know if there is
any condition that is not handled by the above code.

Thanks,
Thomas.

>
> Best Regards,
> Jaehoon Chung
>
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