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

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Date:	Thu, 10 May 2012 20:17:23 +0900
From:	Jaehoon Chung <jh80.chung@...sung.com>
To:	Thomas Abraham <thomas.abraham@...aro.org>
Cc:	Jaehoon Chung <jh80.chung@...sung.com>,
	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 05/10/2012 07:55 PM, Thomas Abraham wrote:

> 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.

Right, the above code is specific for Exynos5250.
But HOLD_REG should be used in other SoC. it's not only Exynos5250 specific.
I want more generic code than specific code for Exynos5250.

Best Regards,
Jaehoon Chung

> 
> 
>> 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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