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    SubjectRe: [RFC PATCH V3 12/21] mmc: sdhci: UHS-II support, add hooks for additional operations
    Adrian, Ben,

    Regarding _reset() function,

    On Fri, Aug 21, 2020 at 05:08:32PM +0300, Adrian Hunter wrote:
    > On 10/07/20 2:10 pm, Ben Chuang wrote:
    > > From: Ben Chuang <ben.chuang@genesyslogic.com.tw>
    > >
    > > In this commit, UHS-II related operations will be called via a function
    > > pointer array, sdhci_uhs2_ops, in order to make UHS-II support as
    > > a kernel module.
    > > This array will be initialized only if CONFIG_MMC_SDHCI_UHS2 is enabled
    > > and when the UHS-II module is loaded. Otherwise, all the functions
    > > stay void.
    > >
    > > Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
    > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
    > > ---
    > > drivers/mmc/host/sdhci.c | 152 ++++++++++++++++++++++++++++++++++-----
    > > 1 file changed, 136 insertions(+), 16 deletions(-)
    > >

    (snip)

    > > if (host->ops->platform_send_init_74_clocks)
    > > host->ops->platform_send_init_74_clocks(host, ios->power_mode);
    > >
    > > @@ -2331,7 +2411,7 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
    > > }
    > >
    > > if (host->version >= SDHCI_SPEC_300) {
    > > - u16 clk, ctrl_2;
    > > + u16 clk;
    > >
    > > if (!host->preset_enabled) {
    > > sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
    > > @@ -3173,11 +3253,19 @@ static bool sdhci_request_done(struct sdhci_host *host)
    > > /* This is to force an update */
    > > host->ops->set_clock(host, host->clock);
    > >
    > > - /* Spec says we should do both at the same time, but Ricoh
    > > - controllers do not like that. */
    > > - sdhci_do_reset(host, SDHCI_RESET_CMD);
    > > - sdhci_do_reset(host, SDHCI_RESET_DATA);
    > > -
    > > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
    > > + host->mmc->flags & MMC_UHS2_INITIALIZED) {
    > > + if (sdhci_uhs2_ops.reset)
    > > + sdhci_uhs2_ops.reset(host,
    > > + SDHCI_UHS2_SW_RESET_SD);
    > > + } else {
    > > + /*
    > > + * Spec says we should do both at the same time, but
    > > + * Ricoh controllers do not like that.
    > > + */
    > > + sdhci_do_reset(host, SDHCI_RESET_CMD);
    > > + sdhci_do_reset(host, SDHCI_RESET_DATA);
    > > + }
    >
    > Please look at using the existing ->reset() sdhci host op instead.

    Well, the second argument to those reset functions is a bit-wise value
    to different "reset" registers, SDHCI_SOFTWARE_RESET and SDHCI_UHS2_SW_RESET,
    respectively.

    This fact raises a couple of questions to me:

    1) Does it make sense to merge two functionality into one, i.e.
    sdhci_do_reset(), which is set to call ->reset hook?

    -> Adrian

    2) UHS2_SW_RESET_SD is done only at this place while there are many callsites
    of reset(RESET_CMD|RESET_DATA) in sdhci.c.
    Why does the current code work?

    I found, in sdhci-pci-gli.c,
    sdhci_gl9755_reset()
    /* reset sd-tran on UHS2 mode if need to reset cmd/data */
    if ((mask & SDHCI_RESET_CMD) | (mask & SDHCI_RESET_DATA))
    gl9755_uhs2_reset_sd_tran(host);

    Is this the trick to avoid the issue?
    (It looks redundant in terms of the hack above in sdhci_request_done()
    and even quite dirty to me. Moreover, no corresponding code for gl9750
    and gl9763.)

    -> Ben

    3) (More or less SD specification issue)
    In UHS-II mode, do we have to call reset(SHCI_RESET_ALL) along with
    reset(UHS2_SW_RESET_FULL)?
    Under the current implementation, both will be called at the end.

    -> Adrian, Ben

    4) (Not directly linked to UHS-II support)
    In some places, we see the sequence:
    sdhci_do_reset(host, SDHCI_RESET_CMD);
    sdhci_do_reset(host, SDHCI_RESET_DATA);
    while in other places,
    sdhci_do_reset(host, SDHCI_RESET_CMD | SDHCI_RESET_DATA);

    If the statement below is true,
    > > - /* Spec says we should do both at the same time, but Ricoh
    > > - controllers do not like that. */
    the latter should be wrong.

    -> Adrian

    -Takahiro Akashi



    > > host->pending_reset = false;
    > > }
    > >
    > > @@ -3532,6 +3620,13 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
    > > SDHCI_INT_BUS_POWER);
    > > sdhci_writel(host, mask, SDHCI_INT_STATUS);
    > >
    > > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
    > > + intmask & SDHCI_INT_ERROR &&
    > > + host->mmc->flags & MMC_UHS2_SUPPORT) {
    > > + if (sdhci_uhs2_ops.irq)
    > > + sdhci_uhs2_ops.irq(host);
    > > + }
    > > +
    >
    > Please look at using the existing ->irq() sdhci host op instead
    >
    > > if (intmask & (SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE)) {
    > > u32 present = sdhci_readl(host, SDHCI_PRESENT_STATE) &
    > > SDHCI_CARD_PRESENT;
    > > @@ -4717,6 +4812,14 @@ int sdhci_setup_host(struct sdhci_host *host)
    > > /* This may alter mmc->*_blk_* parameters */
    > > sdhci_allocate_bounce_buffer(host);
    > >
    > > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
    > > + host->version >= SDHCI_SPEC_400 &&
    > > + sdhci_uhs2_ops.add_host) {
    > > + ret = sdhci_uhs2_ops.add_host(host, host->caps1);
    > > + if (ret)
    > > + goto unreg;
    > > + }
    > > +
    >
    > I think you should look at creating uhs2_add_host() instead
    >
    > > return 0;
    > >
    > > unreg:
    > > @@ -4738,6 +4841,8 @@ void sdhci_cleanup_host(struct sdhci_host *host)
    > > {
    > > struct mmc_host *mmc = host->mmc;
    > >
    > > + /* FIXME: Do we have to do some cleanup for UHS2 here? */
    > > +
    > > if (!IS_ERR(mmc->supply.vqmmc))
    > > regulator_disable(mmc->supply.vqmmc);
    > >
    > > @@ -4766,6 +4871,14 @@ int __sdhci_add_host(struct sdhci_host *host)
    > > mmc->cqe_ops = NULL;
    > > }
    > >
    > > + if ((mmc->caps & MMC_CAP_UHS2) && !host->v4_mode) {
    > > + /* host doesn't want to enable UHS2 support */
    > > + mmc->caps &= ~MMC_CAP_UHS2;
    > > + mmc->flags &= ~MMC_UHS2_SUPPORT;
    > > +
    > > + /* FIXME: Do we have to do some cleanup here? */
    > > + }
    > > +
    > > host->complete_wq = alloc_workqueue("sdhci", flags, 0);
    > > if (!host->complete_wq)
    > > return -ENOMEM;
    > > @@ -4812,6 +4925,9 @@ int __sdhci_add_host(struct sdhci_host *host)
    > > unled:
    > > sdhci_led_unregister(host);
    > > unirq:
    > > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
    > > + sdhci_uhs2_ops.remove_host)
    > > + sdhci_uhs2_ops.remove_host(host, 0);
    > > sdhci_do_reset(host, SDHCI_RESET_ALL);
    > > sdhci_writel(host, 0, SDHCI_INT_ENABLE);
    > > sdhci_writel(host, 0, SDHCI_SIGNAL_ENABLE);
    > > @@ -4869,6 +4985,10 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
    > >
    > > sdhci_led_unregister(host);
    > >
    > > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
    > > + sdhci_uhs2_ops.remove_host)
    > > + sdhci_uhs2_ops.remove_host(host, dead);
    > > +
    >
    > I think you should look at creating uhs2_remove_host() instead
    >
    > > if (!dead)
    > > sdhci_do_reset(host, SDHCI_RESET_ALL);
    > >
    > >
    >

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