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

On Thu, Sep 17, 2020 at 06:12:27PM +0800, Ben Chuang wrote:
> Hi Takahiro,
>
> On Thu, Sep 17, 2020 at 1:12 PM AKASHI Takahiro
> <takahiro.akashi@linaro.org> wrote:
> >
> > 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);

(A)

> >
> > 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.)
>
> GL9755 currently does SD reset and UHS-II reset together.

Do you mean that, in UHS-II operations, you need only the reset on
SDHCI_UHS2_SW_RESET register?
But the hunk above (A) does the UHS-II reset along with UHS-I reset.

> There is no UHS-II interface on gl9750 and gl9763e.
>
> >
> > -> 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.
> >
>
> As I know, the UHS2_SW_RESET_FULL is only for UHS-II.
> Can you list the lines that reset(SHCI_RESET_ALL) and
> reset(UHS2_SW_RESET_FULL) are both called?

I was not clear here. (The above is also another example.)

Look at sdhci_remove_host() and shdci_uhs2_remote_host().
If the argument 'dead' is 0, we will do both of the resets for UHS-II.

-Takahiro Akashi

> > -> 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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