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    SubjectRe: [PATCH 6/10] mmc: sdhci-xenon: Add Marvell Xenon SDHC core functionality
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    Hi Adrian,

    On 2016/10/17 16:14, Adrian Hunter wrote:
    > 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.
    >
    >
    Sure. I will add more detailed comments.
    >>
    >>>>
    >>>>>> + /* 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.
    >
    data->stop and cmd->stop are forced to be NULL if Auto-CMD12 is enabled.
    Instead, currently I use cmd->arg to check if it is a RPMB CMD25. If CMD25 argument is NULL, it should be RPMB access.
    But I only verified it on Marvell platform. Please help check it when later I propose the formal patch.

    >>
    >>>>
    >>>> 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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