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

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Date:   Mon, 20 Mar 2017 08:38:10 +0000
From:   Piotr Sroka <piotrs@...ence.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
CC:     linux-mmc <linux-mmc@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        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



> -----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.
> 
> 
> 
> 
> > 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