linux-kernel - Re: [v2 PATCH 3/3] mmc: sdhci-cadence: Update PHY delay configuration

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Message-ID: <040f3ee3-d715-3696-4f35-6f5b77b6b984@intel.com>
Date:   Wed, 29 Mar 2017 14:59:05 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Piotr Sroka <piotrs@...ence.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-mmc <linux-mmc@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [v2 PATCH 3/3] mmc: sdhci-cadence: Update PHY delay configuration

On 20/03/17 10:38, Piotr Sroka wrote:
> 
> 
>> -----Original Message-----
>> From: Masahiro Yamada [mailto:yamada.masahiro@...ionext.com]
>> Sent: 17 March, 2017 6:23 PM
>> Subject: Re: [v2 PATCH 3/3] mmc: sdhci-cadence: Update PHY delay configuration
>>
>> Hi Piotr,
>>
>> Sorry for my late reply.
>>
>>
>>>
>>> It looks that "input delays" and "DLL sdclk delays" should be defined in dts file because they depend on a chip and a board
>> implementation. On the other hand the less dts properties the better.
>>>
>>> There is one more way to handle input delays. It can be achieved by PHY training. PHY training is similar to the tuning and it should be
>> done when proper timing mode is selected and clock frequency is set.
>>> To make it possible the sdhci_set_ios function need to be global. Then I could create sdhci_cdns_set_ios function as follows:
>>> void sdhci_cdns_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) {
>>>         . . .
>>>
>>>         sdhci_set_ios(mmc, ios);
>>>         /* execute PHY training if needed */
>>>         sdhci_cdns_exec_phy_training(host);
>>> }
>>>
>>> The mmc framework configures timing and frequency separately so PHY training should be executed every time if timing or clock
>> frequency is changed. I am not sure If I can change sdhci_set_ios to global function.
>>
>>
>> I am OK with this, but I hope Adrian can advise us.

There is no problem exporting sdhci_set_ios()

>>
>>
>>
>>
>>> So maybe put all delays to dts file would be a better solution? What do you think?
>>
>> I am OK with DT approach too
>> because this way seems simpler, after all.
>>
>> (My suggestion for data array approach was misleading, sorry.)
>>
> Thanks for review anyway it was useful. Now decision between DTS and data array is more clear for me. 
> 
> Regards 
> Piotr Sroka
>