linux-kernel - Re: [PATCH 7/10] mmc: sdhci-xenon: Add support to PHYs of Marvell Xenon SDHC

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Date:   Mon, 28 Nov 2016 19:38:11 +0800
From:   Ziji Hu <huziji@...vell.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     Gregory CLEMENT <gregory.clement@...e-electrons.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Jason Cooper <jason@...edaemon.net>,
        Andrew Lunn <andrew@...n.ch>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Jimmy Xu <zmxu@...vell.com>,
        Jisheng Zhang <jszhang@...vell.com>,
        Nadav Haklai <nadavh@...vell.com>, Ryan Gao <ygao@...vell.com>,
        Doug Jones <dougj@...vell.com>, Victor Gu <xigu@...vell.com>,
        "Wei(SOCP) Liu" <liuw@...vell.com>,
        Wilson Ding <dingwei@...vell.com>,
        Romain Perier <romain.perier@...e-electrons.com>,
        Yehuda Yitschak <yehuday@...vell.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Hanna Hawa <hannah@...vell.com>,
        Kostya Porotchkin <kostap@...vell.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/10] mmc: sdhci-xenon: Add support to PHYs of Marvell
 Xenon SDHC

Hi Ulf,

On 2016/11/28 19:13, Ulf Hansson wrote:
>>
>>     As you suggest, I replace mmc_wait_for_cmd() with mmc_send_tuning(), to
>>     send commands for testing current sampling point set in our host PHY.
>>
>>     According to my test result, it shows that mmc_send_tuning() can only support
>>     tuning command (CMD21/CMD19).
>>     As a result, we cannot use mmc_send_tuning() when card is in the speed modes
>>     which doesn't support tuning, such as eMMC HS SDR, eMMC HS DRR and
>>     SD SDR 12/SDR25/DDR50. Card will not response to tuning commands in those
>>     speed modes.
>>
>>     Could you please provide suggestions for the speed mode in which tuning is
>>     not available?
>>
> 
> Normally the mmc host driver shouldn't have to care about what the
> card supports, as that is the responsibility of the mmc core to
> manage.
> 
> The host should only need to implement the ->execute_tuning() ops,
> which gets called when the card supports tuning (CMD19/21). Does it
> make sense?
> 
   I think it is irrelevant to tuning procedure.

   Our host requires to adjust PHY setting after each time ios setting
   (SDCLK/bus width/speed mode) is changed.
   The simplified sequence is:
   mmc change ios --> mmc_set_ios() --> ->set_ios() --> after sdhci_set_ios(),
   adjust PHY setting.
   During PHY setting adjustment, out host driver has to send commands to
   test current sampling point. Tuning is another independent step.

   Thus our host needs a valid command in PHY setting adjustment. Tuning command
   can be borrowed to complete this task in SD SDR50. But for other speed mode,
   we have to find out a valid command.

   Any suggestion please?

   Thank you.

Best regards,
Hu Ziji

> Kind regards
> Uffe
>