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

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Message-ID: <d6e1c702-1dfe-3993-da28-01cf01f24b4a@marvell.com>
Date:   Tue, 18 Oct 2016 20:04:51 +0800
From:   Ziji Hu <huziji@...vell.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Gregory CLEMENT <gregory.clement@...e-electrons.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        <linux-mmc@...r.kernel.org>
CC:     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>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        "Jack(SH) Zhu" <jmzhu@...vell.com>, 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>,
        Shiwu Zhang <zhangshw@...vell.com>,
        Victor Gu <xigu@...vell.com>,
        "Wei(SOCP) Liu" <liuw@...vell.com>,
        Wilson Ding <dingwei@...vell.com>,
        Xueping Liu <xpliu@...vell.com>,
        Hilbert Zhang <zzhang@...vell.com>,
        Liuliu Zhao <zhaoliul@...vell.com>,
        Peng Zhu <zhupeng@...vell.com>, Yu Cao <yucao@...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>
Subject: Re: [PATCH 7/10] mmc: sdhci-xenon: Add support to PHYs of Marvell
 Xenon SDHC

Hi Adrian,

On 2016/10/17 15:55, Adrian Hunter wrote:
> On 12/10/16 15:17, Ziji Hu wrote:
>> Hi Adrian,
>>
>> On 2016/10/11 20:39, Adrian Hunter wrote:
<snip>
>>>> +static int __xenon_emmc_delay_adj_test(struct mmc_card *card)
>>>> +{
>>>> +	int err;
>>>> +	u8 *ext_csd = NULL;
>>>> +
>>>> +	err = mmc_get_ext_csd(card, &ext_csd);
>>>> +	kfree(ext_csd);
>>>> +
>>>> +	return err;
>>>> +}
>>>> +
>>>> +static int __xenon_sdio_delay_adj_test(struct mmc_card *card)
>>>> +{
>>>> +	struct mmc_command cmd = {0};
>>>> +	int err;
>>>> +
>>>> +	cmd.opcode = SD_IO_RW_DIRECT;
>>>> +	cmd.flags = MMC_RSP_R5 | MMC_CMD_AC;
>>>> +
>>>> +	err = mmc_wait_for_cmd(card->host, &cmd, 0);
>>>> +	if (err)
>>>> +		return err;
>>>> +
>>>> +	if (cmd.resp[0] & R5_ERROR)
>>>> +		return -EIO;
>>>> +	if (cmd.resp[0] & R5_FUNCTION_NUMBER)
>>>> +		return -EINVAL;
>>>> +	if (cmd.resp[0] & R5_OUT_OF_RANGE)
>>>> +		return -ERANGE;
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static int __xenon_sd_delay_adj_test(struct mmc_card *card)
>>>> +{
>>>> +	struct mmc_command cmd = {0};
>>>> +	int err;
>>>> +
>>>> +	cmd.opcode = MMC_SEND_STATUS;
>>>> +	cmd.arg = card->rca << 16;
>>>> +	cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
>>>> +
>>>> +	err = mmc_wait_for_cmd(card->host, &cmd, 0);
>>>> +	return err;
>>>> +}
>>>> +
>>>> +static int xenon_delay_adj_test(struct mmc_card *card)
>>>> +{
>>>> +	WARN_ON(!card);
>>>> +	WARN_ON(!card->host);
>>>> +
>>>> +	if (mmc_card_mmc(card))
>>>> +		return __xenon_emmc_delay_adj_test(card);
>>>> +	else if (mmc_card_sd(card))
>>>> +		return __xenon_sd_delay_adj_test(card);
>>>> +	else if (mmc_card_sdio(card))
>>>> +		return __xenon_sdio_delay_adj_test(card);
>>>> +	else
>>>> +		return -EINVAL;
>>>> +}
>>>
>>> So you are issuing commands from the ->set_ios() callback.  I would want to
>>> get Ulf's OK for that before going further.
>>>
>> 	Yes, you are correct.
>> 	In some speed mode, Xenon SDHC has to send a series of transfers to search for a perfect sampling point in PHY delay line.
>> 	It is like tuning process.
>>
>>> One thing: you will need to ensure you don't trigger get HS400 re-tuning
>>> because it will call back into ->set_ios().
>>>
>> 	Could you please make the term "HS400 re-tuning" more detailed?
>> 	In current MMC driver, "HS400 re-tuning" will go back to HS200, execute HS200 tuning and come back to HS400.
>> 	I'm sure our Xenon SDHC will not execute it.
> 
> Currently, re-tuning is automatically enabled whenever tuning is executed,
> and then re-tuning will be done periodically or after CRC errors.  The
> function to disable re-tuning mmc_retune_disable() is not exported, however
> if you have you are determining the sampling point your own way, you could
> simply not implement ->execute_tuning() and then there would be no tuning
> and no re-tuning.
>

	It is a little complex in our Xenon SDHC.
	For the speed mode which requests tuning, such as SDR104 and HS200, our driver will execute standard tuning as spec requires.
	However, for those speed mode in which tuning is not requested in spec, our driver has to issues commands to search for the best sampling point.
	
	It seems that HS400 re-tuning/tuning is disabled by default. Is it correct?

>>
>> 	However, in coming eMMC 5.2, there is a real HS400 re-tuning, in which tuning can be directly executed in HS400 mode.
>> 	Our Xenon SDHC will neither trigger this HS400 re-tuning.
>> 	But since so far there is no such feature in MMC driver, I cannot give you a 100% guarantee now.
>>
>>> And you have the problem that you need to get a reference to the card before
>>> the card device has been added.  As I wrote in response to the previous
>>> patch, you should get Ulf's help with that too.
>>>
>> 	Sure.
>> 	I will get card_candidate solved at first.
>> 	Thank you again for your review and help.
>>
>> 	Thank you.
>>
>> Best regards,
>> Hu Ziji
>>>
>>
>