mmc: tegra: Use sdhci_pltfm_clk_get_max_clock

Message ID 1528126540-27004-1-git-send-email-avienamo@nvidia.com
State Accepted
Headers show
Series
  • mmc: tegra: Use sdhci_pltfm_clk_get_max_clock
Related show

Commit Message

Aapo Vienamo June 4, 2018, 3:35 p.m.
The sdhci get_max_clock callback is set to sdhci_pltfm_clk_get_max_clock
and tegra_sdhci_get_max_clock is removed. It appears that the
shdci-tegra specific callback was originally introduced due to the
requirement that the host clock has to be twice the bus clock on DDR50
mode. As far as I can tell the only effect the removal has on DDR50 mode
is in cases where the parent clock is unable to supply the requested
clock rate, causing the DDR50 mode to run at a lower frequency.
Currently the DDR50 mode isn't enabled on any of the SoCs and would also
require configuring the SDHCI clock divider register to function
properly.

The problem with tegra_sdhci_get_max_clock is that it divides the clock
rate by two and thus artificially limits the maximum frequency of faster
signaling modes which don't have the host-bus frequency ratio requirement
of DDR50 such as SDR104 and HS200. Furthermore, the call to
clk_round_rate() may return an error which isn't handled by
tegra_sdhci_get_max_clock.

Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
---
 drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

Comments

Thierry Reding June 5, 2018, 9:28 a.m. | #1
On Mon, Jun 04, 2018 at 06:35:40PM +0300, Aapo Vienamo wrote:
> The sdhci get_max_clock callback is set to sdhci_pltfm_clk_get_max_clock
> and tegra_sdhci_get_max_clock is removed. It appears that the
> shdci-tegra specific callback was originally introduced due to the
> requirement that the host clock has to be twice the bus clock on DDR50
> mode. As far as I can tell the only effect the removal has on DDR50 mode
> is in cases where the parent clock is unable to supply the requested
> clock rate, causing the DDR50 mode to run at a lower frequency.
> Currently the DDR50 mode isn't enabled on any of the SoCs and would also
> require configuring the SDHCI clock divider register to function
> properly.
> 
> The problem with tegra_sdhci_get_max_clock is that it divides the clock
> rate by two and thus artificially limits the maximum frequency of faster
> signaling modes which don't have the host-bus frequency ratio requirement
> of DDR50 such as SDR104 and HS200. Furthermore, the call to
> clk_round_rate() may return an error which isn't handled by
> tegra_sdhci_get_max_clock.
> 
> Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
> ---
>  drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 970d38f6..c8745b5 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -234,17 +234,6 @@ static void tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
>  	sdhci_set_uhs_signaling(host, timing);
>  }
>  
> -static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
> -{
> -	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> -
> -	/*
> -	 * DDR modes require the host to run at double the card frequency, so
> -	 * the maximum rate we can support is half of the module input clock.
> -	 */
> -	return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
> -}

sdhci_pltfm_clk_get_max_clock() returns the current frequency of the
clock, which may not be an accurate maximum.

Also, even if we don't support DDR modes now, we may want to enable them
in the future, at which point we'll need to move to something similar to
the above again, albeit maybe with some of the issues that you mentioned
fixed.

I wonder if we have access to the target mode in this function, because
it seems to me like we'd need to take that into account when determining
the maximum clock rate. Or perhaps the double-rate aspect is already
dealt with in other parts of the MMC subsystem, so the value we should
return here may not even need to take the mode into account.

All of the above said, it is true that we don't enable DDR modes as of
now, and this patch seems like it shouldn't break anything either, so:

Acked-by: Thierry Reding <treding@nvidia.com>

I also gave this a brief run on Jetson TK1 and things seem to work fine,
so:

Tested-by: Thierry Reding <treding@nvidia.com>
Adrian Hunter June 5, 2018, 9:35 a.m. | #2
On 04/06/18 18:35, Aapo Vienamo wrote:
> The sdhci get_max_clock callback is set to sdhci_pltfm_clk_get_max_clock
> and tegra_sdhci_get_max_clock is removed. It appears that the
> shdci-tegra specific callback was originally introduced due to the
> requirement that the host clock has to be twice the bus clock on DDR50
> mode. As far as I can tell the only effect the removal has on DDR50 mode
> is in cases where the parent clock is unable to supply the requested
> clock rate, causing the DDR50 mode to run at a lower frequency.
> Currently the DDR50 mode isn't enabled on any of the SoCs and would also
> require configuring the SDHCI clock divider register to function
> properly.
> 
> The problem with tegra_sdhci_get_max_clock is that it divides the clock
> rate by two and thus artificially limits the maximum frequency of faster
> signaling modes which don't have the host-bus frequency ratio requirement
> of DDR50 such as SDR104 and HS200. Furthermore, the call to
> clk_round_rate() may return an error which isn't handled by
> tegra_sdhci_get_max_clock.
> 
> Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
>  drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 970d38f6..c8745b5 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -234,17 +234,6 @@ static void tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
>  	sdhci_set_uhs_signaling(host, timing);
>  }
>  
> -static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
> -{
> -	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> -
> -	/*
> -	 * DDR modes require the host to run at double the card frequency, so
> -	 * the maximum rate we can support is half of the module input clock.
> -	 */
> -	return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
> -}
> -
>  static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned int tap)
>  {
>  	u32 reg;
> @@ -309,7 +298,7 @@ static const struct sdhci_ops tegra_sdhci_ops = {
>  	.platform_execute_tuning = tegra_sdhci_execute_tuning,
>  	.set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
>  	.voltage_switch = tegra_sdhci_voltage_switch,
> -	.get_max_clock = tegra_sdhci_get_max_clock,
> +	.get_max_clock = sdhci_pltfm_clk_get_max_clock,
>  };
>  
>  static const struct sdhci_pltfm_data sdhci_tegra20_pdata = {
> @@ -357,7 +346,7 @@ static const struct sdhci_ops tegra114_sdhci_ops = {
>  	.platform_execute_tuning = tegra_sdhci_execute_tuning,
>  	.set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
>  	.voltage_switch = tegra_sdhci_voltage_switch,
> -	.get_max_clock = tegra_sdhci_get_max_clock,
> +	.get_max_clock = sdhci_pltfm_clk_get_max_clock,
>  };
>  
>  static const struct sdhci_pltfm_data sdhci_tegra114_pdata = {
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Peter Geis June 5, 2018, 11:58 a.m. | #3
On 06/05/2018 05:28 AM, Thierry Reding wrote:
> On Mon, Jun 04, 2018 at 06:35:40PM +0300, Aapo Vienamo wrote:
>> The sdhci get_max_clock callback is set to sdhci_pltfm_clk_get_max_clock
>> and tegra_sdhci_get_max_clock is removed. It appears that the
>> shdci-tegra specific callback was originally introduced due to the
>> requirement that the host clock has to be twice the bus clock on DDR50
>> mode. As far as I can tell the only effect the removal has on DDR50 mode
>> is in cases where the parent clock is unable to supply the requested
>> clock rate, causing the DDR50 mode to run at a lower frequency.
>> Currently the DDR50 mode isn't enabled on any of the SoCs and would also
>> require configuring the SDHCI clock divider register to function
>> properly.
>>
>> The problem with tegra_sdhci_get_max_clock is that it divides the clock
>> rate by two and thus artificially limits the maximum frequency of faster
>> signaling modes which don't have the host-bus frequency ratio requirement
>> of DDR50 such as SDR104 and HS200. Furthermore, the call to
>> clk_round_rate() may return an error which isn't handled by
>> tegra_sdhci_get_max_clock.
>>
>> Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
>> ---
>>   drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
>>   1 file changed, 2 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
>> index 970d38f6..c8745b5 100644
>> --- a/drivers/mmc/host/sdhci-tegra.c
>> +++ b/drivers/mmc/host/sdhci-tegra.c
>> @@ -234,17 +234,6 @@ static void tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
>>   	sdhci_set_uhs_signaling(host, timing);
>>   }
>>   
>> -static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
>> -{
>> -	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>> -
>> -	/*
>> -	 * DDR modes require the host to run at double the card frequency, so
>> -	 * the maximum rate we can support is half of the module input clock.
>> -	 */
>> -	return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
>> -}
> 
> sdhci_pltfm_clk_get_max_clock() returns the current frequency of the
> clock, which may not be an accurate maximum.
> 
> Also, even if we don't support DDR modes now, we may want to enable them
> in the future, at which point we'll need to move to something similar to
> the above again, albeit maybe with some of the issues that you mentioned
> fixed.
> 
> I wonder if we have access to the target mode in this function, because
> it seems to me like we'd need to take that into account when determining
> the maximum clock rate. Or perhaps the double-rate aspect is already
> dealt with in other parts of the MMC subsystem, so the value we should
> return here may not even need to take the mode into account.
> 
> All of the above said, it is true that we don't enable DDR modes as of
> now, and this patch seems like it shouldn't break anything either, so:
> 
> Acked-by: Thierry Reding <treding@nvidia.com>
> 
> I also gave this a brief run on Jetson TK1 and things seem to work fine,
> so:
> 
> Tested-by: Thierry Reding <treding@nvidia.com>
> 
I am currently testing this in my Ouya project, to see if it makes a 
difference in my eMMC stability above 30Mhz.
As a drop in replacement it works.
I'll be cranking up the speed later.
--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Aapo Vienamo June 5, 2018, 11:58 a.m. | #4
On Tue, 5 Jun 2018 11:28:01 +0200
Thierry Reding <thierry.reding@gmail.com> wrote:

> On Mon, Jun 04, 2018 at 06:35:40PM +0300, Aapo Vienamo wrote:
> > The sdhci get_max_clock callback is set to sdhci_pltfm_clk_get_max_clock
> > and tegra_sdhci_get_max_clock is removed. It appears that the
> > shdci-tegra specific callback was originally introduced due to the
> > requirement that the host clock has to be twice the bus clock on DDR50
> > mode. As far as I can tell the only effect the removal has on DDR50 mode
> > is in cases where the parent clock is unable to supply the requested
> > clock rate, causing the DDR50 mode to run at a lower frequency.
> > Currently the DDR50 mode isn't enabled on any of the SoCs and would also
> > require configuring the SDHCI clock divider register to function
> > properly.
> > 
> > The problem with tegra_sdhci_get_max_clock is that it divides the clock
> > rate by two and thus artificially limits the maximum frequency of faster
> > signaling modes which don't have the host-bus frequency ratio requirement
> > of DDR50 such as SDR104 and HS200. Furthermore, the call to
> > clk_round_rate() may return an error which isn't handled by
> > tegra_sdhci_get_max_clock.
> > 
> > Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
> > ---
> >  drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
> >  1 file changed, 2 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> > index 970d38f6..c8745b5 100644
> > --- a/drivers/mmc/host/sdhci-tegra.c
> > +++ b/drivers/mmc/host/sdhci-tegra.c
> > @@ -234,17 +234,6 @@ static void tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
> >  	sdhci_set_uhs_signaling(host, timing);
> >  }
> >  
> > -static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
> > -{
> > -	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> > -
> > -	/*
> > -	 * DDR modes require the host to run at double the card frequency, so
> > -	 * the maximum rate we can support is half of the module input clock.
> > -	 */
> > -	return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
> > -}  
> 
> sdhci_pltfm_clk_get_max_clock() returns the current frequency of the
> clock, which may not be an accurate maximum.
> 
> Also, even if we don't support DDR modes now, we may want to enable them
> in the future, at which point we'll need to move to something similar to
> the above again, albeit maybe with some of the issues that you mentioned
> fixed.
> 
> I wonder if we have access to the target mode in this function, because
> it seems to me like we'd need to take that into account when determining
> the maximum clock rate. Or perhaps the double-rate aspect is already
> dealt with in other parts of the MMC subsystem, so the value we should
> return here may not even need to take the mode into account.

I don't think that's possible. The callback is only called during probe
from sdhci_setup_host() via sdhci_add_host(). Handling DDR50 properly
might require adding a new SDHCI quirk bit.

> All of the above said, it is true that we don't enable DDR modes as of
> now, and this patch seems like it shouldn't break anything either, so:
> 
> Acked-by: Thierry Reding <treding@nvidia.com>
> 
> I also gave this a brief run on Jetson TK1 and things seem to work fine,
> so:
> 
> Tested-by: Thierry Reding <treding@nvidia.com>

--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Ulf Hansson July 2, 2018, 1:16 p.m. | #5
On 4 June 2018 at 17:35, Aapo Vienamo <avienamo@nvidia.com> wrote:
> The sdhci get_max_clock callback is set to sdhci_pltfm_clk_get_max_clock
> and tegra_sdhci_get_max_clock is removed. It appears that the
> shdci-tegra specific callback was originally introduced due to the
> requirement that the host clock has to be twice the bus clock on DDR50
> mode. As far as I can tell the only effect the removal has on DDR50 mode
> is in cases where the parent clock is unable to supply the requested
> clock rate, causing the DDR50 mode to run at a lower frequency.
> Currently the DDR50 mode isn't enabled on any of the SoCs and would also
> require configuring the SDHCI clock divider register to function
> properly.
>
> The problem with tegra_sdhci_get_max_clock is that it divides the clock
> rate by two and thus artificially limits the maximum frequency of faster
> signaling modes which don't have the host-bus frequency ratio requirement
> of DDR50 such as SDR104 and HS200. Furthermore, the call to
> clk_round_rate() may return an error which isn't handled by
> tegra_sdhci_get_max_clock.
>
> Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>

Thanks, applied for next!

Kind regards
Uffe

> ---
>  drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 970d38f6..c8745b5 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -234,17 +234,6 @@ static void tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
>         sdhci_set_uhs_signaling(host, timing);
>  }
>
> -static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
> -{
> -       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> -
> -       /*
> -        * DDR modes require the host to run at double the card frequency, so
> -        * the maximum rate we can support is half of the module input clock.
> -        */
> -       return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
> -}
> -
>  static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned int tap)
>  {
>         u32 reg;
> @@ -309,7 +298,7 @@ static const struct sdhci_ops tegra_sdhci_ops = {
>         .platform_execute_tuning = tegra_sdhci_execute_tuning,
>         .set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
>         .voltage_switch = tegra_sdhci_voltage_switch,
> -       .get_max_clock = tegra_sdhci_get_max_clock,
> +       .get_max_clock = sdhci_pltfm_clk_get_max_clock,
>  };
>
>  static const struct sdhci_pltfm_data sdhci_tegra20_pdata = {
> @@ -357,7 +346,7 @@ static const struct sdhci_ops tegra114_sdhci_ops = {
>         .platform_execute_tuning = tegra_sdhci_execute_tuning,
>         .set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
>         .voltage_switch = tegra_sdhci_voltage_switch,
> -       .get_max_clock = tegra_sdhci_get_max_clock,
> +       .get_max_clock = sdhci_pltfm_clk_get_max_clock,
>  };
>
>  static const struct sdhci_pltfm_data sdhci_tegra114_pdata = {
> --
> 2.7.4
>
--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Aapo Vienamo July 13, 2018, 9:50 a.m. | #6
On Fri, 13 Jul 2018 01:43:05 +0000
Marcel Ziswiler <marcel.ziswiler@toradex.com> wrote:

> On Mon, 2018-07-02 at 15:16 +0200, Ulf Hansson wrote:
> > On 4 June 2018 at 17:35, Aapo Vienamo <avienamo@nvidia.com> wrote:  
> > > The sdhci get_max_clock callback is set to
> > > sdhci_pltfm_clk_get_max_clock
> > > and tegra_sdhci_get_max_clock is removed. It appears that the
> > > shdci-tegra specific callback was originally introduced due to the
> > > requirement that the host clock has to be twice the bus clock on
> > > DDR50
> > > mode. As far as I can tell the only effect the removal has on DDR50
> > > mode
> > > is in cases where the parent clock is unable to supply the
> > > requested
> > > clock rate, causing the DDR50 mode to run at a lower frequency.
> > > Currently the DDR50 mode isn't enabled on any of the SoCs and would
> > > also
> > > require configuring the SDHCI clock divider register to function
> > > properly.
> > > 
> > > The problem with tegra_sdhci_get_max_clock is that it divides the
> > > clock
> > > rate by two and thus artificially limits the maximum frequency of
> > > faster
> > > signaling modes which don't have the host-bus frequency ratio
> > > requirement
> > > of DDR50 such as SDR104 and HS200. Furthermore, the call to
> > > clk_round_rate() may return an error which isn't handled by
> > > tegra_sdhci_get_max_clock.
> > > 
> > > Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>  
> > 
> > Thanks, applied for next!
> > 
> > Kind regards
> > Uffe
> >   
> > > ---
> > >  drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
> > >  1 file changed, 2 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/mmc/host/sdhci-tegra.c
> > > b/drivers/mmc/host/sdhci-tegra.c
> > > index 970d38f6..c8745b5 100644
> > > --- a/drivers/mmc/host/sdhci-tegra.c
> > > +++ b/drivers/mmc/host/sdhci-tegra.c
> > > @@ -234,17 +234,6 @@ static void
> > > tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
> > >         sdhci_set_uhs_signaling(host, timing);
> > >  }
> > > 
> > > -static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host
> > > *host)
> > > -{
> > > -       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> > > -
> > > -       /*
> > > -        * DDR modes require the host to run at double the card
> > > frequency, so
> > > -        * the maximum rate we can support is half of the module
> > > input clock.
> > > -        */
> > > -       return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
> > > -}
> > > -
> > >  static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned
> > > int tap)
> > >  {
> > >         u32 reg;
> > > @@ -309,7 +298,7 @@ static const struct sdhci_ops tegra_sdhci_ops =
> > > {
> > >         .platform_execute_tuning = tegra_sdhci_execute_tuning,
> > >         .set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
> > >         .voltage_switch = tegra_sdhci_voltage_switch,
> > > -       .get_max_clock = tegra_sdhci_get_max_clock,
> > > +       .get_max_clock = sdhci_pltfm_clk_get_max_clock,
> > >  };
> > > 
> > >  static const struct sdhci_pltfm_data sdhci_tegra20_pdata = {
> > > @@ -357,7 +346,7 @@ static const struct sdhci_ops
> > > tegra114_sdhci_ops = {
> > >         .platform_execute_tuning = tegra_sdhci_execute_tuning,
> > >         .set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
> > >         .voltage_switch = tegra_sdhci_voltage_switch,
> > > -       .get_max_clock = tegra_sdhci_get_max_clock,
> > > +       .get_max_clock = sdhci_pltfm_clk_get_max_clock,
> > >  };
> > > 
> > >  static const struct sdhci_pltfm_data sdhci_tegra114_pdata = {
> > > --
> > > 2.7.4  
> 
> Hm, for us this definitely breaks stuff. While using Stefan's patch set
> [1] we may not only run eMMC at DDR52 even SD cards run stable at
> SDR104. With this patch however the clock gets crippled to 45.33 resp.
> 48 MHz always. This is observed both on Apalis/Colibri T30 as well as
> Apalis TK1.

Well, strictly speaking this isn't a regression as DDR52/50 modes were
not enable at the time when the patch was applied. However, these issues
should be addressed properly none the less.

The patch was written in preparation of implementing support for higher
speed modes like HS200 and HS400, where limiting the max_clock like that
isn't an option. Some other solution than reverting the patch has to be
found.

> Current next-20180712 just with Stefan's 3 patches:
> 
> root@apalis-t30:~# cat /sys/kernel/debug/mmc1/ios 
> clock:          48000000 Hz
> actual clock:   45333333 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      3 (8 bits)
> timing spec:    8 (mmc DDR52)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
> root@apalis-t30:~# hdparm -t /dev/mmcblk1
> 
> /dev/mmcblk1:
>  Timing buffered disk reads: 218 MB in  3.03 seconds =  71.95 MB/sec
> 
> root@apalis-t30:~# cat /sys/kernel/debug/mmc2/ios 
> clock:          48000000 Hz
> actual clock:   48000000 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      2 (4 bits)
> timing spec:    6 (sd uhs SDR104)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
> root@apalis-t30:~# hdparm -t /dev/mmcblk2
> 
> /dev/mmcblk2:
>  Timing buffered disk reads:  66 MB in  3.06 seconds =  21.60 MB/sec
> 
> And with this patch reverted it works as expected again:
> 
> root@apalis-t30:~# cat /sys/kernel/debug/mmc1/ios 
> clock:          52000000 Hz
> actual clock:   51000000 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      3 (8 bits)
> timing spec:    8 (mmc DDR52)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
> root@apalis-t30:~# hdparm -t /dev/mmcblk1
> 
> /dev/mmcblk1:
>  Timing buffered disk reads: 240 MB in  3.02 seconds =  79.50 MB/sec
> 
> root@apalis-t30:~# cat /sys/kernel/debug/mmc2/ios 
> clock:          204000000 Hz
> actual clock:   204000000 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      2 (4 bits)
> timing spec:    6 (sd uhs SDR104)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
> root@apalis-t30:~# hdparm -t /dev/mmcblk2
> 
> /dev/mmcblk2:
>  Timing buffered disk reads: 258 MB in  3.01 seconds =  85.58 MB/sec
> 
> [1] https://lore.kernel.org/lkml/20180712073904.4705-1-stefan@agner.ch

The fact that you're getting totally different clocks, especially on
SDR104, doesn't make much sense. I'll try to reproduce this and track
down what's going on.

 -Aapo

--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Aapo Vienamo July 13, 2018, 12:55 p.m. | #7
On Fri, 13 Jul 2018 01:43:05 +0000
Marcel Ziswiler <marcel.ziswiler@toradex.com> wrote:

> On Mon, 2018-07-02 at 15:16 +0200, Ulf Hansson wrote:
> > On 4 June 2018 at 17:35, Aapo Vienamo <avienamo@nvidia.com> wrote:  
> > > The sdhci get_max_clock callback is set to
> > > sdhci_pltfm_clk_get_max_clock
> > > and tegra_sdhci_get_max_clock is removed. It appears that the
> > > shdci-tegra specific callback was originally introduced due to the
> > > requirement that the host clock has to be twice the bus clock on
> > > DDR50
> > > mode. As far as I can tell the only effect the removal has on DDR50
> > > mode
> > > is in cases where the parent clock is unable to supply the
> > > requested
> > > clock rate, causing the DDR50 mode to run at a lower frequency.
> > > Currently the DDR50 mode isn't enabled on any of the SoCs and would
> > > also
> > > require configuring the SDHCI clock divider register to function
> > > properly.
> > > 
> > > The problem with tegra_sdhci_get_max_clock is that it divides the
> > > clock
> > > rate by two and thus artificially limits the maximum frequency of
> > > faster
> > > signaling modes which don't have the host-bus frequency ratio
> > > requirement
> > > of DDR50 such as SDR104 and HS200. Furthermore, the call to
> > > clk_round_rate() may return an error which isn't handled by
> > > tegra_sdhci_get_max_clock.
> > > 
> > > Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>  
> > 
> > Thanks, applied for next!
> > 
> > Kind regards
> > Uffe
> >   
> > > ---
> > >  drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
> > >  1 file changed, 2 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/mmc/host/sdhci-tegra.c
> > > b/drivers/mmc/host/sdhci-tegra.c
> > > index 970d38f6..c8745b5 100644
> > > --- a/drivers/mmc/host/sdhci-tegra.c
> > > +++ b/drivers/mmc/host/sdhci-tegra.c
> > > @@ -234,17 +234,6 @@ static void
> > > tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
> > >         sdhci_set_uhs_signaling(host, timing);
> > >  }
> > > 
> > > -static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host
> > > *host)
> > > -{
> > > -       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> > > -
> > > -       /*
> > > -        * DDR modes require the host to run at double the card
> > > frequency, so
> > > -        * the maximum rate we can support is half of the module
> > > input clock.
> > > -        */
> > > -       return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
> > > -}
> > > -
> > >  static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned
> > > int tap)
> > >  {
> > >         u32 reg;
> > > @@ -309,7 +298,7 @@ static const struct sdhci_ops tegra_sdhci_ops =
> > > {
> > >         .platform_execute_tuning = tegra_sdhci_execute_tuning,
> > >         .set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
> > >         .voltage_switch = tegra_sdhci_voltage_switch,
> > > -       .get_max_clock = tegra_sdhci_get_max_clock,
> > > +       .get_max_clock = sdhci_pltfm_clk_get_max_clock,
> > >  };
> > > 
> > >  static const struct sdhci_pltfm_data sdhci_tegra20_pdata = {
> > > @@ -357,7 +346,7 @@ static const struct sdhci_ops
> > > tegra114_sdhci_ops = {
> > >         .platform_execute_tuning = tegra_sdhci_execute_tuning,
> > >         .set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
> > >         .voltage_switch = tegra_sdhci_voltage_switch,
> > > -       .get_max_clock = tegra_sdhci_get_max_clock,
> > > +       .get_max_clock = sdhci_pltfm_clk_get_max_clock,
> > >  };
> > > 
> > >  static const struct sdhci_pltfm_data sdhci_tegra114_pdata = {
> > > --
> > > 2.7.4  
> 
> Hm, for us this definitely breaks stuff. While using Stefan's patch set
> [1] we may not only run eMMC at DDR52 even SD cards run stable at
> SDR104. With this patch however the clock gets crippled to 45.33 resp.
> 48 MHz always. This is observed both on Apalis/Colibri T30 as well as
> Apalis TK1.
> 
> Current next-20180712 just with Stefan's 3 patches:
> 
> root@apalis-t30:~# cat /sys/kernel/debug/mmc1/ios 
> clock:          48000000 Hz
> actual clock:   45333333 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      3 (8 bits)
> timing spec:    8 (mmc DDR52)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
> root@apalis-t30:~# hdparm -t /dev/mmcblk1
> 
> /dev/mmcblk1:
>  Timing buffered disk reads: 218 MB in  3.03 seconds =  71.95 MB/sec
> 
> root@apalis-t30:~# cat /sys/kernel/debug/mmc2/ios 
> clock:          48000000 Hz
> actual clock:   48000000 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      2 (4 bits)
> timing spec:    6 (sd uhs SDR104)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
> root@apalis-t30:~# hdparm -t /dev/mmcblk2
> 
> /dev/mmcblk2:
>  Timing buffered disk reads:  66 MB in  3.06 seconds =  21.60 MB/sec
> 
> And with this patch reverted it works as expected again:
> 
> root@apalis-t30:~# cat /sys/kernel/debug/mmc1/ios 
> clock:          52000000 Hz
> actual clock:   51000000 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      3 (8 bits)
> timing spec:    8 (mmc DDR52)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
> root@apalis-t30:~# hdparm -t /dev/mmcblk1
> 
> /dev/mmcblk1:
>  Timing buffered disk reads: 240 MB in  3.02 seconds =  79.50 MB/sec
> 
> root@apalis-t30:~# cat /sys/kernel/debug/mmc2/ios 
> clock:          204000000 Hz
> actual clock:   204000000 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      2 (4 bits)
> timing spec:    6 (sd uhs SDR104)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
> root@apalis-t30:~# hdparm -t /dev/mmcblk2
> 
> /dev/mmcblk2:
>  Timing buffered disk reads: 258 MB in  3.01 seconds =  85.58 MB/sec
> 
> [1] https://lore.kernel.org/lkml/20180712073904.4705-1-stefan@agner.ch

This happens because sdhci_pltfm_clk_get_max_clock() does not actually
return the maximum clock rate but the current one, leading to smaller
clock rates on some platforms. I'll send a patch that fixes this for
sdhci-tegra. Although this raises the question whether the current
behaviour of sdhci_pltfm_clk_get_max_clock() is desirable or not.

 -Aapo
--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Jon Hunter July 13, 2018, 2:04 p.m. | #8
On 13/07/18 13:55, Aapo Vienamo wrote:
> This happens because sdhci_pltfm_clk_get_max_clock() does not actually
> return the maximum clock rate but the current one, leading to smaller
> clock rates on some platforms. I'll send a patch that fixes this for
> sdhci-tegra. Although this raises the question whether the current
> behaviour of sdhci_pltfm_clk_get_max_clock() is desirable or not.

Agree. There is something not right here. 

Cheers,
Jon

Patch

diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 970d38f6..c8745b5 100644
--- a/drivers/mmc/host/sdhci-tegra.c
+++ b/drivers/mmc/host/sdhci-tegra.c
@@ -234,17 +234,6 @@  static void tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
 	sdhci_set_uhs_signaling(host, timing);
 }
 
-static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
-{
-	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
-
-	/*
-	 * DDR modes require the host to run at double the card frequency, so
-	 * the maximum rate we can support is half of the module input clock.
-	 */
-	return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
-}
-
 static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned int tap)
 {
 	u32 reg;
@@ -309,7 +298,7 @@  static const struct sdhci_ops tegra_sdhci_ops = {
 	.platform_execute_tuning = tegra_sdhci_execute_tuning,
 	.set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
 	.voltage_switch = tegra_sdhci_voltage_switch,
-	.get_max_clock = tegra_sdhci_get_max_clock,
+	.get_max_clock = sdhci_pltfm_clk_get_max_clock,
 };
 
 static const struct sdhci_pltfm_data sdhci_tegra20_pdata = {
@@ -357,7 +346,7 @@  static const struct sdhci_ops tegra114_sdhci_ops = {
 	.platform_execute_tuning = tegra_sdhci_execute_tuning,
 	.set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
 	.voltage_switch = tegra_sdhci_voltage_switch,
-	.get_max_clock = tegra_sdhci_get_max_clock,
+	.get_max_clock = sdhci_pltfm_clk_get_max_clock,
 };
 
 static const struct sdhci_pltfm_data sdhci_tegra114_pdata = {