From: AKASHI Takahiro <[email protected]>
sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
and not for UHS-II mode.
Signed-off-by: Ben Chuang <[email protected]>
Signed-off-by: AKASHI Takahiro <[email protected]>
---
drivers/mmc/host/sdhci.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 5511649946b9..7f2537648a08 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
/*
* Signal Voltage Switching is only applicable for Host Controllers
* v3.00 and above.
+ * But for UHS2, the signal voltage is supplied by vdd2 which is
+ * already 1.8v so no voltage switch required.
*/
- if (host->version < SDHCI_SPEC_300)
+ if (host->version < SDHCI_SPEC_300 ||
+ (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
+ host->version >= SDHCI_SPEC_400 &&
+ host->mmc->flags & MMC_UHS2_SUPPORT))
return 0;
ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
--
2.27.0
On 10/07/20 2:11 pm, Ben Chuang wrote:
> From: AKASHI Takahiro <[email protected]>
>
> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> and not for UHS-II mode.
>
> Signed-off-by: Ben Chuang <[email protected]>
> Signed-off-by: AKASHI Takahiro <[email protected]>
> ---
> drivers/mmc/host/sdhci.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 5511649946b9..7f2537648a08 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> /*
> * Signal Voltage Switching is only applicable for Host Controllers
> * v3.00 and above.
> + * But for UHS2, the signal voltage is supplied by vdd2 which is
> + * already 1.8v so no voltage switch required.
> */
> - if (host->version < SDHCI_SPEC_300)
> + if (host->version < SDHCI_SPEC_300 ||
> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> + host->version >= SDHCI_SPEC_400 &&
> + host->mmc->flags & MMC_UHS2_SUPPORT))
Please look at hooking ->start_signal_voltage_switch() instead
> return 0;
>
> ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>
Adrian,
On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
> On 10/07/20 2:11 pm, Ben Chuang wrote:
> > From: AKASHI Takahiro <[email protected]>
> >
> > sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> > and not for UHS-II mode.
> >
> > Signed-off-by: Ben Chuang <[email protected]>
> > Signed-off-by: AKASHI Takahiro <[email protected]>
> > ---
> > drivers/mmc/host/sdhci.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index 5511649946b9..7f2537648a08 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> > /*
> > * Signal Voltage Switching is only applicable for Host Controllers
> > * v3.00 and above.
> > + * But for UHS2, the signal voltage is supplied by vdd2 which is
> > + * already 1.8v so no voltage switch required.
> > */
> > - if (host->version < SDHCI_SPEC_300)
> > + if (host->version < SDHCI_SPEC_300 ||
> > + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > + host->version >= SDHCI_SPEC_400 &&
> > + host->mmc->flags & MMC_UHS2_SUPPORT))
>
> Please look at hooking ->start_signal_voltage_switch() instead
Do you mean that you want every platform driver who wants to support UHS-II
to set NULL to start_signal_voltage_switch hook even if this hack is
platform agnostic?
(Another option is that it would be put in sdhci_uhs2_add_host() which
is responsible to set MMC_UHS2_SUPPORT.)
-Takahiro Akashi
>
>
> > return 0;
> >
> > ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> >
>
On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> Adrian,
>
> On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
>> On 10/07/20 2:11 pm, Ben Chuang wrote:
>>> From: AKASHI Takahiro <[email protected]>
>>>
>>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
>>> and not for UHS-II mode.
>>>
>>> Signed-off-by: Ben Chuang <[email protected]>
>>> Signed-off-by: AKASHI Takahiro <[email protected]>
>>> ---
>>> drivers/mmc/host/sdhci.c | 7 ++++++-
>>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>> index 5511649946b9..7f2537648a08 100644
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
>>> /*
>>> * Signal Voltage Switching is only applicable for Host Controllers
>>> * v3.00 and above.
>>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
>>> + * already 1.8v so no voltage switch required.
>>> */
>>> - if (host->version < SDHCI_SPEC_300)
>>> + if (host->version < SDHCI_SPEC_300 ||
>>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
>>> + host->version >= SDHCI_SPEC_400 &&
>>> + host->mmc->flags & MMC_UHS2_SUPPORT))
>>
>> Please look at hooking ->start_signal_voltage_switch() instead
>
> Do you mean that you want every platform driver who wants to support UHS-II
> to set NULL to start_signal_voltage_switch hook even if this hack is
> platform agnostic?
No, I see UHS-II as a separate layer i.e.
UHS-II host controller driver
| |
| v
| sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
| |
v v
sdhci e.g. sdhci_start_signal_voltage_switch
Most things should go through sdhci-uhs2 but not nessarily everything.
Ben, Adrian,
On Mon, Sep 14, 2020 at 11:08:14AM +0300, Adrian Hunter wrote:
> On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> > Adrian,
> >
> > On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
> >> On 10/07/20 2:11 pm, Ben Chuang wrote:
> >>> From: AKASHI Takahiro <[email protected]>
> >>>
> >>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> >>> and not for UHS-II mode.
> >>>
> >>> Signed-off-by: Ben Chuang <[email protected]>
> >>> Signed-off-by: AKASHI Takahiro <[email protected]>
> >>> ---
> >>> drivers/mmc/host/sdhci.c | 7 ++++++-
> >>> 1 file changed, 6 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> >>> index 5511649946b9..7f2537648a08 100644
> >>> --- a/drivers/mmc/host/sdhci.c
> >>> +++ b/drivers/mmc/host/sdhci.c
> >>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> >>> /*
> >>> * Signal Voltage Switching is only applicable for Host Controllers
> >>> * v3.00 and above.
> >>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
> >>> + * already 1.8v so no voltage switch required.
I have been confused with this comment.
(I know it came from the original Intel code, not from Ben.)
If this comment is true,
> >>> */
> >>> - if (host->version < SDHCI_SPEC_300)
> >>> + if (host->version < SDHCI_SPEC_300 ||
> >>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> >>> + host->version >= SDHCI_SPEC_400 &&
> >>> + host->mmc->flags & MMC_UHS2_SUPPORT))
the condition above must be wrong since 'flags & MMC_UHS2_SUPPORT'
is one of capabilities for a host controller, not a card
while the selection of voltage depends on a card type.
So I wonder why this code still works.
I guess that it is because set_signal_voltage(), or other variant functions,
will never be called for UHS-II cards under the current implementation.
Looking at mmc_sd_init_card(), we have added some hack:
mmc_sd_init_card()
{
...
/* For UHS2, skip the UHS-I initialization. */
if ((host->flags & MMC_UHS2_SUPPORT) &&
(host->flags & MMC_UHS2_INITIALIZED))
goto done;
...
if (mmc_sd_card_using_v18(card)) {
if (mmc_host_set_uhs_voltage(host) ||
mmc_sd_init_uhs_card(card)) {
...
}
Ben, can you confirm this?
(There is another callsite of mmc_host_set_uhs_voltage() though.)
> >> Please look at hooking ->start_signal_voltage_switch() instead
> >
> > Do you mean that you want every platform driver who wants to support UHS-II
> > to set NULL to start_signal_voltage_switch hook even if this hack is
> > platform agnostic?
>
> No, I see UHS-II as a separate layer i.e.
>
> UHS-II host controller driver
> | |
> | v
> | sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
> | |
> v v
> sdhci e.g. sdhci_start_signal_voltage_switch
>
> Most things should go through sdhci-uhs2 but not nessarily everything.
What I meant by my previous comment is that we don't have to
call any function, sdhci_uhs2_start_signal_voltage_switch in above example,
for UHS-II cards in any case since it is always simply empty.
-Takahiro Akashi
Hi Takahiro,
On Tue, Sep 15, 2020 at 2:03 PM AKASHI Takahiro
<[email protected]> wrote:
>
> Ben, Adrian,
>
> On Mon, Sep 14, 2020 at 11:08:14AM +0300, Adrian Hunter wrote:
> > On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> > > Adrian,
> > >
> > > On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
> > >> On 10/07/20 2:11 pm, Ben Chuang wrote:
> > >>> From: AKASHI Takahiro <[email protected]>
> > >>>
> > >>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> > >>> and not for UHS-II mode.
> > >>>
> > >>> Signed-off-by: Ben Chuang <[email protected]>
> > >>> Signed-off-by: AKASHI Takahiro <[email protected]>
> > >>> ---
> > >>> drivers/mmc/host/sdhci.c | 7 ++++++-
> > >>> 1 file changed, 6 insertions(+), 1 deletion(-)
> > >>>
> > >>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > >>> index 5511649946b9..7f2537648a08 100644
> > >>> --- a/drivers/mmc/host/sdhci.c
> > >>> +++ b/drivers/mmc/host/sdhci.c
> > >>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> > >>> /*
> > >>> * Signal Voltage Switching is only applicable for Host Controllers
> > >>> * v3.00 and above.
> > >>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
> > >>> + * already 1.8v so no voltage switch required.
>
> I have been confused with this comment.
> (I know it came from the original Intel code, not from Ben.)
>
> If this comment is true,
>
> > >>> */
> > >>> - if (host->version < SDHCI_SPEC_300)
> > >>> + if (host->version < SDHCI_SPEC_300 ||
> > >>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > >>> + host->version >= SDHCI_SPEC_400 &&
> > >>> + host->mmc->flags & MMC_UHS2_SUPPORT))
>
> the condition above must be wrong since 'flags & MMC_UHS2_SUPPORT'
> is one of capabilities for a host controller, not a card
> while the selection of voltage depends on a card type.
The flag MMC_UHS2_SUPPORT is set at the beginning of mmc_uhs2_rescan_try_freq().
In UHS-II flow, it stays set.
If the attempt to UHS-II fails finally, it will be unset.
>
> So I wonder why this code still works.
> I guess that it is because set_signal_voltage(), or other variant functions,
> will never be called for UHS-II cards under the current implementation.
>
> Looking at mmc_sd_init_card(), we have added some hack:
> mmc_sd_init_card()
> {
> ...
> /* For UHS2, skip the UHS-I initialization. */
> if ((host->flags & MMC_UHS2_SUPPORT) &&
> (host->flags & MMC_UHS2_INITIALIZED))
> goto done;
> ...
> if (mmc_sd_card_using_v18(card)) {
> if (mmc_host_set_uhs_voltage(host) ||
> mmc_sd_init_uhs_card(card)) {
> ...
> }
>
> Ben, can you confirm this?
> (There is another callsite of mmc_host_set_uhs_voltage() though.)
UHS-II cards use differential signals and don't need to signal voltage switch.
But the main task is to set the parameters of UHS-II card interface.
>
> > >> Please look at hooking ->start_signal_voltage_switch() instead
> > >
> > > Do you mean that you want every platform driver who wants to support UHS-II
> > > to set NULL to start_signal_voltage_switch hook even if this hack is
> > > platform agnostic?
> >
> > No, I see UHS-II as a separate layer i.e.
> >
> > UHS-II host controller driver
> > | |
> > | v
> > | sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
> > | |
> > v v
> > sdhci e.g. sdhci_start_signal_voltage_switch
> >
> > Most things should go through sdhci-uhs2 but not nessarily everything.
>
> What I meant by my previous comment is that we don't have to
> call any function, sdhci_uhs2_start_signal_voltage_switch in above example,
> for UHS-II cards in any case since it is always simply empty.
>
> -Takahiro Akashi
On Tue, Sep 15, 2020 at 07:36:14PM +0800, Ben Chuang wrote:
> Hi Takahiro,
>
> On Tue, Sep 15, 2020 at 2:03 PM AKASHI Takahiro
> <[email protected]> wrote:
> >
> > Ben, Adrian,
> >
> > On Mon, Sep 14, 2020 at 11:08:14AM +0300, Adrian Hunter wrote:
> > > On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> > > > Adrian,
> > > >
> > > > On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
> > > >> On 10/07/20 2:11 pm, Ben Chuang wrote:
> > > >>> From: AKASHI Takahiro <[email protected]>
> > > >>>
> > > >>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> > > >>> and not for UHS-II mode.
> > > >>>
> > > >>> Signed-off-by: Ben Chuang <[email protected]>
> > > >>> Signed-off-by: AKASHI Takahiro <[email protected]>
> > > >>> ---
> > > >>> drivers/mmc/host/sdhci.c | 7 ++++++-
> > > >>> 1 file changed, 6 insertions(+), 1 deletion(-)
> > > >>>
> > > >>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > > >>> index 5511649946b9..7f2537648a08 100644
> > > >>> --- a/drivers/mmc/host/sdhci.c
> > > >>> +++ b/drivers/mmc/host/sdhci.c
> > > >>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> > > >>> /*
> > > >>> * Signal Voltage Switching is only applicable for Host Controllers
> > > >>> * v3.00 and above.
> > > >>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
> > > >>> + * already 1.8v so no voltage switch required.
> >
> > I have been confused with this comment.
> > (I know it came from the original Intel code, not from Ben.)
> >
> > If this comment is true,
> >
> > > >>> */
> > > >>> - if (host->version < SDHCI_SPEC_300)
> > > >>> + if (host->version < SDHCI_SPEC_300 ||
> > > >>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > > >>> + host->version >= SDHCI_SPEC_400 &&
> > > >>> + host->mmc->flags & MMC_UHS2_SUPPORT))
> >
> > the condition above must be wrong since 'flags & MMC_UHS2_SUPPORT'
> > is one of capabilities for a host controller, not a card
> > while the selection of voltage depends on a card type.
>
> The flag MMC_UHS2_SUPPORT is set at the beginning of mmc_uhs2_rescan_try_freq().
> In UHS-II flow, it stays set.
> If the attempt to UHS-II fails finally, it will be unset.
Right, but MMC_UHS2_SUPPORT is also set, at least initially,
in sdhci_uhs2_add_host(). It is confusing, isn't it?
As we discussed before, any card-specific properties, like UHS-II mode,
should be placed in a card structure, not a host structure.
> >
> > So I wonder why this code still works.
> > I guess that it is because set_signal_voltage(), or other variant functions,
> > will never be called for UHS-II cards under the current implementation.
> >
> > Looking at mmc_sd_init_card(), we have added some hack:
> > mmc_sd_init_card()
> > {
> > ...
> > /* For UHS2, skip the UHS-I initialization. */
> > if ((host->flags & MMC_UHS2_SUPPORT) &&
> > (host->flags & MMC_UHS2_INITIALIZED))
> > goto done;
> > ...
> > if (mmc_sd_card_using_v18(card)) {
> > if (mmc_host_set_uhs_voltage(host) ||
> > mmc_sd_init_uhs_card(card)) {
> > ...
> > }
> >
> > Ben, can you confirm this?
> > (There is another callsite of mmc_host_set_uhs_voltage() though.)
>
> UHS-II cards use differential signals and don't need to signal voltage switch.
> But the main task is to set the parameters of UHS-II card interface.
Whoever sets MMC_UHS2_SUPPORT (and MMC_UHS2_INITIALIZED), my assertion above
(mmc_host_set_uhs_voltage, and hence [sdhci_]start_signal_voltage_switch(), is
never called for UHS-II cards) will be valid, isn't it?
-Takahiro Akashi
> >
> > > >> Please look at hooking ->start_signal_voltage_switch() instead
> > > >
> > > > Do you mean that you want every platform driver who wants to support UHS-II
> > > > to set NULL to start_signal_voltage_switch hook even if this hack is
> > > > platform agnostic?
> > >
> > > No, I see UHS-II as a separate layer i.e.
> > >
> > > UHS-II host controller driver
> > > | |
> > > | v
> > > | sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
> > > | |
> > > v v
> > > sdhci e.g. sdhci_start_signal_voltage_switch
> > >
> > > Most things should go through sdhci-uhs2 but not nessarily everything.
> >
> > What I meant by my previous comment is that we don't have to
> > call any function, sdhci_uhs2_start_signal_voltage_switch in above example,
> > for UHS-II cards in any case since it is always simply empty.
> >
> > -Takahiro Akashi
On Wed, Sep 16, 2020 at 09:01:20AM +0300, Adrian Hunter wrote:
> On 15/09/20 9:03 am, AKASHI Takahiro wrote:
> > Ben, Adrian,
> >
> > On Mon, Sep 14, 2020 at 11:08:14AM +0300, Adrian Hunter wrote:
> >> On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> >>> Adrian,
> >>>
> >>> On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
> >>>> On 10/07/20 2:11 pm, Ben Chuang wrote:
> >>>>> From: AKASHI Takahiro <[email protected]>
> >>>>>
> >>>>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> >>>>> and not for UHS-II mode.
> >>>>>
> >>>>> Signed-off-by: Ben Chuang <[email protected]>
> >>>>> Signed-off-by: AKASHI Takahiro <[email protected]>
> >>>>> ---
> >>>>> drivers/mmc/host/sdhci.c | 7 ++++++-
> >>>>> 1 file changed, 6 insertions(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> >>>>> index 5511649946b9..7f2537648a08 100644
> >>>>> --- a/drivers/mmc/host/sdhci.c
> >>>>> +++ b/drivers/mmc/host/sdhci.c
> >>>>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> >>>>> /*
> >>>>> * Signal Voltage Switching is only applicable for Host Controllers
> >>>>> * v3.00 and above.
> >>>>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
> >>>>> + * already 1.8v so no voltage switch required.
> >>>>> */
> >>>>> - if (host->version < SDHCI_SPEC_300)
> >>>>> + if (host->version < SDHCI_SPEC_300 ||
> >>>>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> >>>>> + host->version >= SDHCI_SPEC_400 &&
> >>>>> + host->mmc->flags & MMC_UHS2_SUPPORT))
> >>>> Please look at hooking ->start_signal_voltage_switch() instead
> >>>
> >>> Do you mean that you want every platform driver who wants to support UHS-II
> >>> to set NULL to start_signal_voltage_switch hook even if this hack is
> >>> platform agnostic?
> >>
> >> No, I see UHS-II as a separate layer i.e.
> >>
> >> UHS-II host controller driver
> >> | |
> >> | v
> >> | sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
> >> | |
> >> v v
> >> sdhci e.g. sdhci_start_signal_voltage_switch
> >>
> >> Most things should go through sdhci-uhs2 but not nessarily everything.
> >
> > What I meant by my previous comment is that we don't have to
> > call any function, sdhci_uhs2_start_signal_voltage_switch in above example,
> > for UHS-II cards in any case since it is always simply empty.
>
> Please treat the sdhci_uhs2_... host ops as functions for a UHS-II host
> controller in either UHS-II or legacy mode. i.e. it is up to sdhci-uhs2.c to
> call through to sdhci.c not the other way around. e.g.
>
> int sdhci_uhs2_start_signal_voltage_switch(blah)
> {
> if (sdhci_uhs2_mode(host))
> return 0;
> return sdhci_start_signal_valtage_switch(blah);
> }
Okay, the remaining issue is to clarify the meaning of MMC_UHS2_SUPPORT.
-Takhiro Akashi
On Wed, Sep 16, 2020 at 8:52 AM AKASHI Takahiro
<[email protected]> wrote:
>
> On Tue, Sep 15, 2020 at 07:36:14PM +0800, Ben Chuang wrote:
> > Hi Takahiro,
> >
> > On Tue, Sep 15, 2020 at 2:03 PM AKASHI Takahiro
> > <[email protected]> wrote:
> > >
> > > Ben, Adrian,
> > >
> > > On Mon, Sep 14, 2020 at 11:08:14AM +0300, Adrian Hunter wrote:
> > > > On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> > > > > Adrian,
> > > > >
> > > > > On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
> > > > >> On 10/07/20 2:11 pm, Ben Chuang wrote:
> > > > >>> From: AKASHI Takahiro <[email protected]>
> > > > >>>
> > > > >>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> > > > >>> and not for UHS-II mode.
> > > > >>>
> > > > >>> Signed-off-by: Ben Chuang <[email protected]>
> > > > >>> Signed-off-by: AKASHI Takahiro <[email protected]>
> > > > >>> ---
> > > > >>> drivers/mmc/host/sdhci.c | 7 ++++++-
> > > > >>> 1 file changed, 6 insertions(+), 1 deletion(-)
> > > > >>>
> > > > >>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > > > >>> index 5511649946b9..7f2537648a08 100644
> > > > >>> --- a/drivers/mmc/host/sdhci.c
> > > > >>> +++ b/drivers/mmc/host/sdhci.c
> > > > >>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> > > > >>> /*
> > > > >>> * Signal Voltage Switching is only applicable for Host Controllers
> > > > >>> * v3.00 and above.
> > > > >>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
> > > > >>> + * already 1.8v so no voltage switch required.
> > >
> > > I have been confused with this comment.
> > > (I know it came from the original Intel code, not from Ben.)
> > >
> > > If this comment is true,
> > >
> > > > >>> */
> > > > >>> - if (host->version < SDHCI_SPEC_300)
> > > > >>> + if (host->version < SDHCI_SPEC_300 ||
> > > > >>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > > > >>> + host->version >= SDHCI_SPEC_400 &&
> > > > >>> + host->mmc->flags & MMC_UHS2_SUPPORT))
> > >
> > > the condition above must be wrong since 'flags & MMC_UHS2_SUPPORT'
> > > is one of capabilities for a host controller, not a card
> > > while the selection of voltage depends on a card type.
> >
> > The flag MMC_UHS2_SUPPORT is set at the beginning of mmc_uhs2_rescan_try_freq().
> > In UHS-II flow, it stays set.
> > If the attempt to UHS-II fails finally, it will be unset.
>
> Right, but MMC_UHS2_SUPPORT is also set, at least initially,
> in sdhci_uhs2_add_host(). It is confusing, isn't it?
I think it can be removed from sdhci_uhs2_add_host() to avoid making confusion.
>
> As we discussed before, any card-specific properties, like UHS-II mode,
> should be placed in a card structure, not a host structure.
>
> > >
> > > So I wonder why this code still works.
> > > I guess that it is because set_signal_voltage(), or other variant functions,
> > > will never be called for UHS-II cards under the current implementation.
> > >
> > > Looking at mmc_sd_init_card(), we have added some hack:
> > > mmc_sd_init_card()
> > > {
> > > ...
> > > /* For UHS2, skip the UHS-I initialization. */
> > > if ((host->flags & MMC_UHS2_SUPPORT) &&
> > > (host->flags & MMC_UHS2_INITIALIZED))
> > > goto done;
> > > ...
> > > if (mmc_sd_card_using_v18(card)) {
> > > if (mmc_host_set_uhs_voltage(host) ||
> > > mmc_sd_init_uhs_card(card)) {
> > > ...
> > > }
> > >
> > > Ben, can you confirm this?
> > > (There is another callsite of mmc_host_set_uhs_voltage() though.)
> >
> > UHS-II cards use differential signals and don't need to signal voltage switch.
> > But the main task is to set the parameters of UHS-II card interface.
>
> Whoever sets MMC_UHS2_SUPPORT (and MMC_UHS2_INITIALIZED), my assertion above
> (mmc_host_set_uhs_voltage, and hence [sdhci_]start_signal_voltage_switch(), is
> never called for UHS-II cards) will be valid, isn't it?
>
> -Takahiro Akashi
>
> > >
> > > > >> Please look at hooking ->start_signal_voltage_switch() instead
> > > > >
> > > > > Do you mean that you want every platform driver who wants to support UHS-II
> > > > > to set NULL to start_signal_voltage_switch hook even if this hack is
> > > > > platform agnostic?
> > > >
> > > > No, I see UHS-II as a separate layer i.e.
> > > >
> > > > UHS-II host controller driver
> > > > | |
> > > > | v
> > > > | sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
> > > > | |
> > > > v v
> > > > sdhci e.g. sdhci_start_signal_voltage_switch
> > > >
> > > > Most things should go through sdhci-uhs2 but not nessarily everything.
> > >
> > > What I meant by my previous comment is that we don't have to
> > > call any function, sdhci_uhs2_start_signal_voltage_switch in above example,
> > > for UHS-II cards in any case since it is always simply empty.
> > >
> > > -Takahiro Akashi
Ben,
On Wed, Sep 16, 2020 at 05:42:07PM +0800, Ben Chuang wrote:
> On Wed, Sep 16, 2020 at 8:52 AM AKASHI Takahiro
> <[email protected]> wrote:
> >
> > On Tue, Sep 15, 2020 at 07:36:14PM +0800, Ben Chuang wrote:
> > > Hi Takahiro,
> > >
> > > On Tue, Sep 15, 2020 at 2:03 PM AKASHI Takahiro
> > > <[email protected]> wrote:
> > > >
> > > > Ben, Adrian,
> > > >
> > > > On Mon, Sep 14, 2020 at 11:08:14AM +0300, Adrian Hunter wrote:
> > > > > On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> > > > > > Adrian,
> > > > > >
> > > > > > On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
> > > > > >> On 10/07/20 2:11 pm, Ben Chuang wrote:
> > > > > >>> From: AKASHI Takahiro <[email protected]>
> > > > > >>>
> > > > > >>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> > > > > >>> and not for UHS-II mode.
> > > > > >>>
> > > > > >>> Signed-off-by: Ben Chuang <[email protected]>
> > > > > >>> Signed-off-by: AKASHI Takahiro <[email protected]>
> > > > > >>> ---
> > > > > >>> drivers/mmc/host/sdhci.c | 7 ++++++-
> > > > > >>> 1 file changed, 6 insertions(+), 1 deletion(-)
> > > > > >>>
> > > > > >>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > > > > >>> index 5511649946b9..7f2537648a08 100644
> > > > > >>> --- a/drivers/mmc/host/sdhci.c
> > > > > >>> +++ b/drivers/mmc/host/sdhci.c
> > > > > >>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> > > > > >>> /*
> > > > > >>> * Signal Voltage Switching is only applicable for Host Controllers
> > > > > >>> * v3.00 and above.
> > > > > >>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
> > > > > >>> + * already 1.8v so no voltage switch required.
> > > >
> > > > I have been confused with this comment.
> > > > (I know it came from the original Intel code, not from Ben.)
> > > >
> > > > If this comment is true,
> > > >
> > > > > >>> */
> > > > > >>> - if (host->version < SDHCI_SPEC_300)
> > > > > >>> + if (host->version < SDHCI_SPEC_300 ||
> > > > > >>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > > > > >>> + host->version >= SDHCI_SPEC_400 &&
> > > > > >>> + host->mmc->flags & MMC_UHS2_SUPPORT))
> > > >
> > > > the condition above must be wrong since 'flags & MMC_UHS2_SUPPORT'
> > > > is one of capabilities for a host controller, not a card
> > > > while the selection of voltage depends on a card type.
> > >
> > > The flag MMC_UHS2_SUPPORT is set at the beginning of mmc_uhs2_rescan_try_freq().
> > > In UHS-II flow, it stays set.
> > > If the attempt to UHS-II fails finally, it will be unset.
> >
> > Right, but MMC_UHS2_SUPPORT is also set, at least initially,
> > in sdhci_uhs2_add_host(). It is confusing, isn't it?
>
> I think it can be removed from sdhci_uhs2_add_host() to avoid making confusion.
Okay,
> >
> > As we discussed before, any card-specific properties, like UHS-II mode,
> > should be placed in a card structure, not a host structure.
Do you have any idea on this?
I remember that Ulf also made a similar comment on the "core" side.
-Takahiro Akashi
> >
> > > >
> > > > So I wonder why this code still works.
> > > > I guess that it is because set_signal_voltage(), or other variant functions,
> > > > will never be called for UHS-II cards under the current implementation.
> > > >
> > > > Looking at mmc_sd_init_card(), we have added some hack:
> > > > mmc_sd_init_card()
> > > > {
> > > > ...
> > > > /* For UHS2, skip the UHS-I initialization. */
> > > > if ((host->flags & MMC_UHS2_SUPPORT) &&
> > > > (host->flags & MMC_UHS2_INITIALIZED))
> > > > goto done;
> > > > ...
> > > > if (mmc_sd_card_using_v18(card)) {
> > > > if (mmc_host_set_uhs_voltage(host) ||
> > > > mmc_sd_init_uhs_card(card)) {
> > > > ...
> > > > }
> > > >
> > > > Ben, can you confirm this?
> > > > (There is another callsite of mmc_host_set_uhs_voltage() though.)
> > >
> > > UHS-II cards use differential signals and don't need to signal voltage switch.
> > > But the main task is to set the parameters of UHS-II card interface.
> >
> > Whoever sets MMC_UHS2_SUPPORT (and MMC_UHS2_INITIALIZED), my assertion above
> > (mmc_host_set_uhs_voltage, and hence [sdhci_]start_signal_voltage_switch(), is
> > never called for UHS-II cards) will be valid, isn't it?
> >
> > -Takahiro Akashi
> >
> > > >
> > > > > >> Please look at hooking ->start_signal_voltage_switch() instead
> > > > > >
> > > > > > Do you mean that you want every platform driver who wants to support UHS-II
> > > > > > to set NULL to start_signal_voltage_switch hook even if this hack is
> > > > > > platform agnostic?
> > > > >
> > > > > No, I see UHS-II as a separate layer i.e.
> > > > >
> > > > > UHS-II host controller driver
> > > > > | |
> > > > > | v
> > > > > | sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
> > > > > | |
> > > > > v v
> > > > > sdhci e.g. sdhci_start_signal_voltage_switch
> > > > >
> > > > > Most things should go through sdhci-uhs2 but not nessarily everything.
> > > >
> > > > What I meant by my previous comment is that we don't have to
> > > > call any function, sdhci_uhs2_start_signal_voltage_switch in above example,
> > > > for UHS-II cards in any case since it is always simply empty.
> > > >
> > > > -Takahiro Akashi
On Thu, Sep 17, 2020 at 8:56 AM AKASHI Takahiro
<[email protected]> wrote:
>
> Ben,
>
> On Wed, Sep 16, 2020 at 05:42:07PM +0800, Ben Chuang wrote:
> > On Wed, Sep 16, 2020 at 8:52 AM AKASHI Takahiro
> > <[email protected]> wrote:
> > >
> > > On Tue, Sep 15, 2020 at 07:36:14PM +0800, Ben Chuang wrote:
> > > > Hi Takahiro,
> > > >
> > > > On Tue, Sep 15, 2020 at 2:03 PM AKASHI Takahiro
> > > > <[email protected]> wrote:
> > > > >
> > > > > Ben, Adrian,
> > > > >
> > > > > On Mon, Sep 14, 2020 at 11:08:14AM +0300, Adrian Hunter wrote:
> > > > > > On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> > > > > > > Adrian,
> > > > > > >
> > > > > > > On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
> > > > > > >> On 10/07/20 2:11 pm, Ben Chuang wrote:
> > > > > > >>> From: AKASHI Takahiro <[email protected]>
> > > > > > >>>
> > > > > > >>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
> > > > > > >>> and not for UHS-II mode.
> > > > > > >>>
> > > > > > >>> Signed-off-by: Ben Chuang <[email protected]>
> > > > > > >>> Signed-off-by: AKASHI Takahiro <[email protected]>
> > > > > > >>> ---
> > > > > > >>> drivers/mmc/host/sdhci.c | 7 ++++++-
> > > > > > >>> 1 file changed, 6 insertions(+), 1 deletion(-)
> > > > > > >>>
> > > > > > >>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > > > > > >>> index 5511649946b9..7f2537648a08 100644
> > > > > > >>> --- a/drivers/mmc/host/sdhci.c
> > > > > > >>> +++ b/drivers/mmc/host/sdhci.c
> > > > > > >>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
> > > > > > >>> /*
> > > > > > >>> * Signal Voltage Switching is only applicable for Host Controllers
> > > > > > >>> * v3.00 and above.
> > > > > > >>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
> > > > > > >>> + * already 1.8v so no voltage switch required.
> > > > >
> > > > > I have been confused with this comment.
> > > > > (I know it came from the original Intel code, not from Ben.)
> > > > >
> > > > > If this comment is true,
> > > > >
> > > > > > >>> */
> > > > > > >>> - if (host->version < SDHCI_SPEC_300)
> > > > > > >>> + if (host->version < SDHCI_SPEC_300 ||
> > > > > > >>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > > > > > >>> + host->version >= SDHCI_SPEC_400 &&
> > > > > > >>> + host->mmc->flags & MMC_UHS2_SUPPORT))
> > > > >
> > > > > the condition above must be wrong since 'flags & MMC_UHS2_SUPPORT'
> > > > > is one of capabilities for a host controller, not a card
> > > > > while the selection of voltage depends on a card type.
> > > >
> > > > The flag MMC_UHS2_SUPPORT is set at the beginning of mmc_uhs2_rescan_try_freq().
> > > > In UHS-II flow, it stays set.
> > > > If the attempt to UHS-II fails finally, it will be unset.
> > >
> > > Right, but MMC_UHS2_SUPPORT is also set, at least initially,
> > > in sdhci_uhs2_add_host(). It is confusing, isn't it?
> >
> > I think it can be removed from sdhci_uhs2_add_host() to avoid making confusion.
>
> Okay,
>
> > >
> > > As we discussed before, any card-specific properties, like UHS-II mode,
> > > should be placed in a card structure, not a host structure.
>
> Do you have any idea on this?
> I remember that Ulf also made a similar comment on the "core" side.
We may list those properties to do first. i.e. MMC_UHS2_INITIALIZED.
>
> -Takahiro Akashi
>
> > >
> > > > >
> > > > > So I wonder why this code still works.
> > > > > I guess that it is because set_signal_voltage(), or other variant functions,
> > > > > will never be called for UHS-II cards under the current implementation.
> > > > >
> > > > > Looking at mmc_sd_init_card(), we have added some hack:
> > > > > mmc_sd_init_card()
> > > > > {
> > > > > ...
> > > > > /* For UHS2, skip the UHS-I initialization. */
> > > > > if ((host->flags & MMC_UHS2_SUPPORT) &&
> > > > > (host->flags & MMC_UHS2_INITIALIZED))
> > > > > goto done;
> > > > > ...
> > > > > if (mmc_sd_card_using_v18(card)) {
> > > > > if (mmc_host_set_uhs_voltage(host) ||
> > > > > mmc_sd_init_uhs_card(card)) {
> > > > > ...
> > > > > }
> > > > >
> > > > > Ben, can you confirm this?
> > > > > (There is another callsite of mmc_host_set_uhs_voltage() though.)
> > > >
> > > > UHS-II cards use differential signals and don't need to signal voltage switch.
> > > > But the main task is to set the parameters of UHS-II card interface.
> > >
> > > Whoever sets MMC_UHS2_SUPPORT (and MMC_UHS2_INITIALIZED), my assertion above
> > > (mmc_host_set_uhs_voltage, and hence [sdhci_]start_signal_voltage_switch(), is
> > > never called for UHS-II cards) will be valid, isn't it?
> > >
> > > -Takahiro Akashi
> > >
> > > > >
> > > > > > >> Please look at hooking ->start_signal_voltage_switch() instead
> > > > > > >
> > > > > > > Do you mean that you want every platform driver who wants to support UHS-II
> > > > > > > to set NULL to start_signal_voltage_switch hook even if this hack is
> > > > > > > platform agnostic?
> > > > > >
> > > > > > No, I see UHS-II as a separate layer i.e.
> > > > > >
> > > > > > UHS-II host controller driver
> > > > > > | |
> > > > > > | v
> > > > > > | sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
> > > > > > | |
> > > > > > v v
> > > > > > sdhci e.g. sdhci_start_signal_voltage_switch
> > > > > >
> > > > > > Most things should go through sdhci-uhs2 but not nessarily everything.
> > > > >
> > > > > What I meant by my previous comment is that we don't have to
> > > > > call any function, sdhci_uhs2_start_signal_voltage_switch in above example,
> > > > > for UHS-II cards in any case since it is always simply empty.
> > > > >
> > > > > -Takahiro Akashi