Message-ID: <ec7a2658-5af3-bff8-3cb8-adb72406df5c@intel.com>
Date:   Mon, 17 Oct 2016 11:14:22 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Ziji Hu <huziji@...vell.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 6/10] mmc: sdhci-xenon: Add Marvell Xenon SDHC core
 functionality

On 13/10/16 08:38, Ziji Hu wrote:
> Hi Adrian,
> 
> On 2016/10/12 21:07, Adrian Hunter wrote:
>> On 12/10/16 14:58, Ziji Hu wrote:
>>> Hi Adrian,
>>>
>>> 	Thank you very much for your review.
>>> 	I will firstly fix the typo.
>>>
>>> On 2016/10/11 20:37, Adrian Hunter wrote:
> <snip>
>>>>> +
>>>>> +static int xenon_start_signal_voltage_switch(struct mmc_host *mmc,
>>>>> +					     struct mmc_ios *ios)
>>>>> +{
>>>>> +	struct sdhci_host *host = mmc_priv(mmc);
>>>>> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>>>>> +	struct sdhci_xenon_priv *priv = sdhci_pltfm_priv(pltfm_host);
>>>>> +
>>>>> +	/*
>>>>> +	 * Before SD/SDIO set signal voltage, SD bus clock should be
>>>>> +	 * disabled. However, sdhci_set_clock will also disable the Internal
>>>>> +	 * clock in mmc_set_signal_voltage().
>>>>> +	 * If Internal clock is disabled, the 3.3V/1.8V bit can not be updated.
>>>>> +	 * Thus here manually enable internal clock.
>>>>> +	 *
>>>>> +	 * After switch completes, it is unnecessary to disable internal clock,
>>>>> +	 * since keeping internal clock active obeys SD spec.
>>>>> +	 */
>>>>> +	enable_xenon_internal_clk(host);
>>>>> +
>>>>> +	if (priv->card_candidate) {
>>>>
>>>> mmc_power_up() calls __mmc_set_signal_voltage() calls
>>>> host->ops->start_signal_voltage_switch so priv->card_candidate could be an
>>>> invalid reference to an old card.
>>>>
>>>> So that's not going to work if the card changes - not only for removable
>>>> cards but even for eMMC if init fails and retries.
>>>>
>>> 	As you point out, this piece of code have defects, even though it actually works on Marvell multiple platforms, unless eMMC card is removable.
>>>
>>> 	I can add a property to explicitly indicate eMMC type in DTS.
>>> 	Then card_candidate access can be removed here.
>>> 	Does it sounds more reasonable to you?
>>
>> Sure
>>
>>>
>>>>> +		if (mmc_card_mmc(priv->card_candidate))
>>>>> +			return xenon_emmc_signal_voltage_switch(mmc, ios);
>>>>
>>>> So if all you need to know is whether it is a eMMC, why can't DT tell you?
>>>>
>>> 	I can add an eMMC type property in DTS, to remove the card_candidate access here.
>>>
>>>>> +	}
>>>>> +
>>>>> +	return sdhci_start_signal_voltage_switch(mmc, ios);
>>>>> +}
>>>>> +
>>>>> +/*
>>>>> + * After determining which slot is used for SDIO,
>>>>> + * some additional task is required.
>>>>> + */
>>>>> +static void xenon_init_card(struct mmc_host *mmc, struct mmc_card *card)
>>>>> +{
>>>>> +	struct sdhci_host *host = mmc_priv(mmc);
>>>>> +	u32 reg;
>>>>> +	u8 slot_idx;
>>>>> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>>>>> +	struct sdhci_xenon_priv *priv = sdhci_pltfm_priv(pltfm_host);
>>>>> +
>>>>> +	/* Link the card for delay adjustment */
>>>>> +	priv->card_candidate = card;
>>>>
>>>> You really need a better way to get the card.  I suggest you take up the
>>>> issue with Ulf.  One possibility is to have mmc core set host->card = card
>>>> much earlier.
>>>>
>>> 	Could you please tell me if any issue related to card_candidate still exists, after the card_candidate is removed from xenon_start_signal_voltage_switch() in above?
>>> 	It seems that when init_card is called, the structure card has already been updated and stable in MMC/SD/SDIO initialization sequence.
>>> 	May I keep it here?
>>
>> It works by accident rather than by design.  We can do better.
>>
> 	Could you please tell me some details which are satisfied about card_candidate?
> 
> 	I must admit that card_candidate in xenon_start_signal_voltage_switch() is imperfect.
> 	But card_candidate in init_card() and later in set_ios() work by design, rather than by accident. We did a lot of tests on several platforms.
> 	
> 	The structure mmc_card passed in here is a stable one. Thus in my very own opinion, it is safe and stable to use mmc_card here.
> 	card_candidate is used only in card initialization. It is not active in later transfers after initialization is done.
> 	It will always updated with mmc_card in next card initialization.

Ok, so maybe just add some comments and more explanation of how it works.


> 
>>>
>>>>> +	/* Set tuning functionality of this slot */
>>>>> +	xenon_slot_tuning_setup(host);
>>>>> +
>>>>> +	slot_idx = priv->slot_idx;
>>>>> +	if (!mmc_card_sdio(card)) {
>>>>> +		/* Re-enable the Auto-CMD12 cap flag. */
>>>>> +		host->quirks |= SDHCI_QUIRK_MULTIBLOCK_READ_ACMD12;
>>>>> +		host->flags |= SDHCI_AUTO_CMD12;
>>>>> +
>>>>> +		/* Clear SDIO Card Inserted indication */
>>>>> +		reg = sdhci_readl(host, SDHC_SYS_CFG_INFO);
>>>>> +		reg &= ~(1 << (slot_idx + SLOT_TYPE_SDIO_SHIFT));
>>>>> +		sdhci_writel(host, reg, SDHC_SYS_CFG_INFO);
>>>>> +
>>>>> +		if (mmc_card_mmc(card)) {
>>>>> +			mmc->caps |= MMC_CAP_NONREMOVABLE;
>>>>> +			if (!(host->quirks2 & SDHCI_QUIRK2_NO_1_8_V))
>>>>> +				mmc->caps |= MMC_CAP_1_8V_DDR;
>>>>> +			/*
>>>>> +			 * Force to clear BUS_TEST to
>>>>> +			 * skip bus_test_pre and bus_test_post
>>>>> +			 */
>>>>> +			mmc->caps &= ~MMC_CAP_BUS_WIDTH_TEST;
>>>>> +			mmc->caps2 |= MMC_CAP2_HC_ERASE_SZ |
>>>>> +				      MMC_CAP2_PACKED_CMD;
>>>>> +			if (mmc->caps & MMC_CAP_8_BIT_DATA)
>>>>> +				mmc->caps2 |= MMC_CAP2_HS400_1_8V;
>>>>> +		}
>>>>> +	} else {
>>>>> +		/*
>>>>> +		 * Delete the Auto-CMD12 cap flag.
>>>>> +		 * Otherwise, when sending multi-block CMD53,
>>>>> +		 * Driver will set Transfer Mode Register to enable Auto CMD12.
>>>>> +		 * However, SDIO device cannot recognize CMD12.
>>>>> +		 * Thus SDHC will time-out for waiting for CMD12 response.
>>>>> +		 */
>>>>> +		host->quirks &= ~SDHCI_QUIRK_MULTIBLOCK_READ_ACMD12;
>>>>> +		host->flags &= ~SDHCI_AUTO_CMD12;
>>>>
>>>> sdhci_set_transfer_mode() won't enable auto-CMD12 for CMD53 anyway, so is
>>>> this needed?
>>>>
>>> 	In Xenon driver, Auto-CMD12 flag is set to enable full support to Auto-CMD feature, both Auto-CMD12 and Auto-CMD23.
>>> 	As a result, when Xenon SDHC slot can both support SD and SDIO, Auto-CMD12 is disabled when SDIO card is inserted, and renabled when SD is inserted.
>>>
>>> 	I recheck the sdhci code to set Auto-CMD bit in Transfer Mode register, in sdhci_set_transfer_mode():
>>> 	if (mmc_op_multi(cmd->opcode) || data->blocks > 1)
>>> 	As you can see, as long as it is CMD18/CMD25 OR there are multiple data blocks, Auto-CMD field will be set.
>>> 	CMD53 doesn't have CMD23. Thus Auto-CMD12 is selected since Auto-CMD12 flag is set.
>>> 	Thus I have to clear Auto-CMD12 to avoid issuing Auto-CMD12 in SDIO transfer.
>>
>>
>> The code is:
>>
>> 	if (mmc_op_multi(cmd->opcode) || data->blocks > 1) {
>> 		mode = SDHCI_TRNS_BLK_CNT_EN | SDHCI_TRNS_MULTI;
>> 		/*
>> 		 * If we are sending CMD23, CMD12 never gets sent
>> 		 * on successful completion (so no Auto-CMD12).
>> 		 */
>> 		if (sdhci_auto_cmd12(host, cmd->mrq) &&
>> 		    (cmd->opcode != SD_IO_RW_EXTENDED))
>> 			mode |= SDHCI_TRNS_AUTO_CMD12;
>> 		else if (cmd->mrq->sbc && (host->flags & SDHCI_AUTO_CMD23)) {
>> 			mode |= SDHCI_TRNS_AUTO_CMD23;
>> 			sdhci_writel(host, cmd->mrq->sbc->arg, SDHCI_ARGUMENT2);
>> 		}
>> 	}
>>
>> You can see the check for SD_IO_RW_EXTENDED which is CMD53.
>>
> 	Sorry. I didn't notice CMD53 check was added.
> 	I introduced this Auto-CMD12 hack since kernel 3.8. It seems that this check is not added in kernel 3.8.
> 	Thanks for the information. I will remove the Auto-CMD12 hack.
> 
>>>
>>> 	I just meet a similar issue in RPMB.
>>> 	When Auto-CMD12 flag is set, eMMC RPMB access will trigger Auto-CMD12, since CMD25 is in use.
>>> 	It will cause RPMB access failed.
>>
>> Can you explain more about the RPMB issue.  Doesn't it use CMD23, so CMD12
>> wouldn't be used - auto or manually.
>>
> 	RPMB go through the MMC ioctl routine.
> 	Unlike normal data transfer, MMC ioctl for RPMB explicitly issues CMD23. When CMD25 is issued, there is neither data->sbc nor Auto-CMD23.
> 	As a result, sdhci driver will automatically enable Auto-CMD12 for RPMB CMD25 if Auto-CMD12 flag is set.

OK, so SDHCI should also not allow auto-cmd12 if there is no stop command
i.e. data->stop is null.

> 
>>>
>>> 	One possible solution is to drop Auto-CMD12 support and use Auto-CMD23 only, in Xenon driver.
>>> 	May I know you opinion, please?
>>
>> I don't use auto-CMD12 because I don't know if it provides any benefit and
>> sdhci does not seem to have implemented Auto CMD12 Error Recovery, although
>> I have never looked at it closely.
>>
> 	Actually, Auto-CMD23 is always used on our Xenon. Auto-CMD12 is not used at all.
> 	But since this driver is a general one for all Marvell products, Auto-CMD12 is also supported in case that Auto-CMD23 is not available.
>  
> 

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