Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Andrey Pronin]

On Wed, Jul 20, 2016 at 01:54:22PM -0600, Jason Gunthorpe wrote:
> On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote:
> 
> > Sorry, I just updated this patch description in v2 to indicate why they are 
> > not
> > hard-coded, but didn't answer explicitly. As the firmware changes, a 
> > different
> > revision of it can have a different time before it sleeps in its 
> > configuration,
> > or the time it takes it to startup may be different. Thus, there's a way to
> > set it here w/o changing the driver.
> 
> This sort of stuff should be read out of the firmware, not DT..
> 
> Why has Google created such a non-standard TPM firmware???
> 
> Jason

Thanks, Jason. Will hard-code those in the driver instead of reading
from DT.

Andrey

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Andrey Pronin]

On Wed, Jul 20, 2016 at 01:54:22PM -0600, Jason Gunthorpe wrote:
> On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote:
> 
> > Sorry, I just updated this patch description in v2 to indicate why they are 
> > not
> > hard-coded, but didn't answer explicitly. As the firmware changes, a 
> > different
> > revision of it can have a different time before it sleeps in its 
> > configuration,
> > or the time it takes it to startup may be different. Thus, there's a way to
> > set it here w/o changing the driver.
> 
> This sort of stuff should be read out of the firmware, not DT..
> 
> Why has Google created such a non-standard TPM firmware???
> 
> Jason

Thanks, Jason. Will hard-code those in the driver instead of reading
from DT.

Andrey

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Andrey Pronin]

On Thu, Jul 21, 2016 at 04:03:12PM -0500, Rob Herring wrote:
> On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote:
> > On Wed, Jul 20, 2016 at 02:03:03PM -0500, Rob Herring wrote:
> > > On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote:
> > 
> > Hi Rob,
> > 
> > > As I mentioned, there may be common properties. It doesn't seem you 
> > > looked, so I did:
> > > 
> > > - spi-rx-delay-us  - (optional) Microsecond delay after a read transfer.
> > > - spi-tx-delay-us  - (optional) Microsecond delay after a write transfer.
> > > 
> > > Seems to me setting one or both of these should work for you.
> > >
> > 
> > Yes, good catch, my fault I didn't see those.
> > But they are not exactly what I mean and need. I don't need delay after
> > each read or write transfer. What is needed is a guaranteed time
> > between transfers.
> > 
> > So, if the next transaction doesn't come withing the next X ms (or us),
> > we don't waste time on inserting a delays after this transaction at all.
> > Following the description and always inserting a delay must work well
> > for short microseconds-long delays. For longer milliseconds-long delays
> > a different strategy of checking the time when the previous transaction
> > was and only delaying if it was not too long ago is better.
> 
> I'd guess that the intent is the same for all. A simple delay is 
> just much easier to implement. I would think implementing the more 
> sophisticated algorithm would work for all users. Perhaps with some 
> threshold for a simple delay.
> 
> > Thus, I won't be able to re-use these properties anyways based on their
> > current description in bindings/spi/spi-bus.txt.
> > 
> > > > +- sleep-delay-ms: Time after the last SPI activity, after which the 
> > > > chip
> > > > +  may go to sleep.
> > > > +- wake-start-delay-ms: Time after initiating wake up before the chip is
> > > > +  ready to accept commands over SPI.
> > > 
> > > I also asked why these 2 can't be hard-coded in the driver?
> > >
> > 
> > Sorry, I just updated this patch description in v2 to indicate why they are 
> > not
> > hard-coded, but didn't answer explicitly. As the firmware changes, a 
> > different
> > revision of it can have a different time before it sleeps in its 
> > configuration,
> > or the time it takes it to startup may be different. Thus, there's a way to
> > set it here w/o changing the driver.
> 
> The firmware and DT may not be updated in sync especially if you are 
> loading the firmware from the rootfs. Are you doing DT and firmware 
> updates without changing the kernel?
> 
> Rob

Hi Rob,

Thanks for the feedback. I will hard-code those parameters in the
driver instead of reading from DT.

Thanks,
Andrey

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Andrey Pronin]

On Thu, Jul 21, 2016 at 04:03:12PM -0500, Rob Herring wrote:
> On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote:
> > On Wed, Jul 20, 2016 at 02:03:03PM -0500, Rob Herring wrote:
> > > On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote:
> > 
> > Hi Rob,
> > 
> > > As I mentioned, there may be common properties. It doesn't seem you 
> > > looked, so I did:
> > > 
> > > - spi-rx-delay-us  - (optional) Microsecond delay after a read transfer.
> > > - spi-tx-delay-us  - (optional) Microsecond delay after a write transfer.
> > > 
> > > Seems to me setting one or both of these should work for you.
> > >
> > 
> > Yes, good catch, my fault I didn't see those.
> > But they are not exactly what I mean and need. I don't need delay after
> > each read or write transfer. What is needed is a guaranteed time
> > between transfers.
> > 
> > So, if the next transaction doesn't come withing the next X ms (or us),
> > we don't waste time on inserting a delays after this transaction at all.
> > Following the description and always inserting a delay must work well
> > for short microseconds-long delays. For longer milliseconds-long delays
> > a different strategy of checking the time when the previous transaction
> > was and only delaying if it was not too long ago is better.
> 
> I'd guess that the intent is the same for all. A simple delay is 
> just much easier to implement. I would think implementing the more 
> sophisticated algorithm would work for all users. Perhaps with some 
> threshold for a simple delay.
> 
> > Thus, I won't be able to re-use these properties anyways based on their
> > current description in bindings/spi/spi-bus.txt.
> > 
> > > > +- sleep-delay-ms: Time after the last SPI activity, after which the 
> > > > chip
> > > > +  may go to sleep.
> > > > +- wake-start-delay-ms: Time after initiating wake up before the chip is
> > > > +  ready to accept commands over SPI.
> > > 
> > > I also asked why these 2 can't be hard-coded in the driver?
> > >
> > 
> > Sorry, I just updated this patch description in v2 to indicate why they are 
> > not
> > hard-coded, but didn't answer explicitly. As the firmware changes, a 
> > different
> > revision of it can have a different time before it sleeps in its 
> > configuration,
> > or the time it takes it to startup may be different. Thus, there's a way to
> > set it here w/o changing the driver.
> 
> The firmware and DT may not be updated in sync especially if you are 
> loading the firmware from the rootfs. Are you doing DT and firmware 
> updates without changing the kernel?
> 
> Rob

Hi Rob,

Thanks for the feedback. I will hard-code those parameters in the
driver instead of reading from DT.

Thanks,
Andrey

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Rob Herring]

On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote:
> On Wed, Jul 20, 2016 at 02:03:03PM -0500, Rob Herring wrote:
> > On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote:
> 
> Hi Rob,
> 
> > As I mentioned, there may be common properties. It doesn't seem you 
> > looked, so I did:
> > 
> > - spi-rx-delay-us  - (optional) Microsecond delay after a read transfer.
> > - spi-tx-delay-us  - (optional) Microsecond delay after a write transfer.
> > 
> > Seems to me setting one or both of these should work for you.
> >
> 
> Yes, good catch, my fault I didn't see those.
> But they are not exactly what I mean and need. I don't need delay after
> each read or write transfer. What is needed is a guaranteed time
> between transfers.
> 
> So, if the next transaction doesn't come withing the next X ms (or us),
> we don't waste time on inserting a delays after this transaction at all.
> Following the description and always inserting a delay must work well
> for short microseconds-long delays. For longer milliseconds-long delays
> a different strategy of checking the time when the previous transaction
> was and only delaying if it was not too long ago is better.

I'd guess that the intent is the same for all. A simple delay is 
just much easier to implement. I would think implementing the more 
sophisticated algorithm would work for all users. Perhaps with some 
threshold for a simple delay.

> Thus, I won't be able to re-use these properties anyways based on their
> current description in bindings/spi/spi-bus.txt.
> 
> > > +- sleep-delay-ms: Time after the last SPI activity, after which the chip
> > > +  may go to sleep.
> > > +- wake-start-delay-ms: Time after initiating wake up before the chip is
> > > +  ready to accept commands over SPI.
> > 
> > I also asked why these 2 can't be hard-coded in the driver?
> >
> 
> Sorry, I just updated this patch description in v2 to indicate why they are 
> not
> hard-coded, but didn't answer explicitly. As the firmware changes, a different
> revision of it can have a different time before it sleeps in its 
> configuration,
> or the time it takes it to startup may be different. Thus, there's a way to
> set it here w/o changing the driver.

The firmware and DT may not be updated in sync especially if you are 
loading the firmware from the rootfs. Are you doing DT and firmware 
updates without changing the kernel?

Rob

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Rob Herring]

On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote:
> On Wed, Jul 20, 2016 at 02:03:03PM -0500, Rob Herring wrote:
> > On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote:
> 
> Hi Rob,
> 
> > As I mentioned, there may be common properties. It doesn't seem you 
> > looked, so I did:
> > 
> > - spi-rx-delay-us  - (optional) Microsecond delay after a read transfer.
> > - spi-tx-delay-us  - (optional) Microsecond delay after a write transfer.
> > 
> > Seems to me setting one or both of these should work for you.
> >
> 
> Yes, good catch, my fault I didn't see those.
> But they are not exactly what I mean and need. I don't need delay after
> each read or write transfer. What is needed is a guaranteed time
> between transfers.
> 
> So, if the next transaction doesn't come withing the next X ms (or us),
> we don't waste time on inserting a delays after this transaction at all.
> Following the description and always inserting a delay must work well
> for short microseconds-long delays. For longer milliseconds-long delays
> a different strategy of checking the time when the previous transaction
> was and only delaying if it was not too long ago is better.

I'd guess that the intent is the same for all. A simple delay is 
just much easier to implement. I would think implementing the more 
sophisticated algorithm would work for all users. Perhaps with some 
threshold for a simple delay.

> Thus, I won't be able to re-use these properties anyways based on their
> current description in bindings/spi/spi-bus.txt.
> 
> > > +- sleep-delay-ms: Time after the last SPI activity, after which the chip
> > > +  may go to sleep.
> > > +- wake-start-delay-ms: Time after initiating wake up before the chip is
> > > +  ready to accept commands over SPI.
> > 
> > I also asked why these 2 can't be hard-coded in the driver?
> >
> 
> Sorry, I just updated this patch description in v2 to indicate why they are 
> not
> hard-coded, but didn't answer explicitly. As the firmware changes, a different
> revision of it can have a different time before it sleeps in its 
> configuration,
> or the time it takes it to startup may be different. Thus, there's a way to
> set it here w/o changing the driver.

The firmware and DT may not be updated in sync especially if you are 
loading the firmware from the rootfs. Are you doing DT and firmware 
updates without changing the kernel?

Rob

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Jason Gunthorpe]

On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote:

> Sorry, I just updated this patch description in v2 to indicate why they are 
> not
> hard-coded, but didn't answer explicitly. As the firmware changes, a different
> revision of it can have a different time before it sleeps in its 
> configuration,
> or the time it takes it to startup may be different. Thus, there's a way to
> set it here w/o changing the driver.

This sort of stuff should be read out of the firmware, not DT..

Why has Google created such a non-standard TPM firmware???

Jason

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Jason Gunthorpe]

On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote:

> Sorry, I just updated this patch description in v2 to indicate why they are 
> not
> hard-coded, but didn't answer explicitly. As the firmware changes, a different
> revision of it can have a different time before it sleeps in its 
> configuration,
> or the time it takes it to startup may be different. Thus, there's a way to
> set it here w/o changing the driver.

This sort of stuff should be read out of the firmware, not DT..

Why has Google created such a non-standard TPM firmware???

Jason

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Andrey Pronin]

On Wed, Jul 20, 2016 at 02:03:03PM -0500, Rob Herring wrote:
> On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote:

Hi Rob,

> As I mentioned, there may be common properties. It doesn't seem you 
> looked, so I did:
> 
> - spi-rx-delay-us  - (optional) Microsecond delay after a read transfer.
> - spi-tx-delay-us  - (optional) Microsecond delay after a write transfer.
> 
> Seems to me setting one or both of these should work for you.
>

Yes, good catch, my fault I didn't see those.
But they are not exactly what I mean and need. I don't need delay after
each read or write transfer. What is needed is a guaranteed time
between transfers.

So, if the next transaction doesn't come withing the next X ms (or us),
we don't waste time on inserting a delays after this transaction at all.
Following the description and always inserting a delay must work well
for short microseconds-long delays. For longer milliseconds-long delays
a different strategy of checking the time when the previous transaction
was and only delaying if it was not too long ago is better.

Thus, I won't be able to re-use these properties anyways based on their
current description in bindings/spi/spi-bus.txt.

> > +- sleep-delay-ms: Time after the last SPI activity, after which the chip
> > +  may go to sleep.
> > +- wake-start-delay-ms: Time after initiating wake up before the chip is
> > +  ready to accept commands over SPI.
> 
> I also asked why these 2 can't be hard-coded in the driver?
>

Sorry, I just updated this patch description in v2 to indicate why they are not
hard-coded, but didn't answer explicitly. As the firmware changes, a different
revision of it can have a different time before it sleeps in its configuration,
or the time it takes it to startup may be different. Thus, there's a way to
set it here w/o changing the driver.

Andrey

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Andrey Pronin]

On Wed, Jul 20, 2016 at 02:03:03PM -0500, Rob Herring wrote:
> On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote:

Hi Rob,

> As I mentioned, there may be common properties. It doesn't seem you 
> looked, so I did:
> 
> - spi-rx-delay-us  - (optional) Microsecond delay after a read transfer.
> - spi-tx-delay-us  - (optional) Microsecond delay after a write transfer.
> 
> Seems to me setting one or both of these should work for you.
>

Yes, good catch, my fault I didn't see those.
But they are not exactly what I mean and need. I don't need delay after
each read or write transfer. What is needed is a guaranteed time
between transfers.

So, if the next transaction doesn't come withing the next X ms (or us),
we don't waste time on inserting a delays after this transaction at all.
Following the description and always inserting a delay must work well
for short microseconds-long delays. For longer milliseconds-long delays
a different strategy of checking the time when the previous transaction
was and only delaying if it was not too long ago is better.

Thus, I won't be able to re-use these properties anyways based on their
current description in bindings/spi/spi-bus.txt.

> > +- sleep-delay-ms: Time after the last SPI activity, after which the chip
> > +  may go to sleep.
> > +- wake-start-delay-ms: Time after initiating wake up before the chip is
> > +  ready to accept commands over SPI.
> 
> I also asked why these 2 can't be hard-coded in the driver?
>

Sorry, I just updated this patch description in v2 to indicate why they are not
hard-coded, but didn't answer explicitly. As the firmware changes, a different
revision of it can have a different time before it sleeps in its configuration,
or the time it takes it to startup may be different. Thus, there's a way to
set it here w/o changing the driver.

Andrey

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Rob Herring]

On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote:
> Add TPM2.0 PTP FIFO compatible SPI interface for chips with Cr50
> firmware. Several timing-related properties that may differ from
> one firmware version to another are added to devicetree.
> Document these properties.
> 
> Signed-off-by: Andrey Pronin 
> ---
>  .../devicetree/bindings/security/tpm/cr50_spi.txt  | 32 
> ++
>  1 file changed, 32 insertions(+)
>  create mode 100644 
> Documentation/devicetree/bindings/security/tpm/cr50_spi.txt
> 
> diff --git a/Documentation/devicetree/bindings/security/tpm/cr50_spi.txt 
> b/Documentation/devicetree/bindings/security/tpm/cr50_spi.txt
> new file mode 100644
> index 000..f212b6b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/security/tpm/cr50_spi.txt
> @@ -0,0 +1,32 @@
> +* H1 Secure Microcontroller with Cr50 Firmware on SPI Bus.
> +
> +H1 Secure Microcontroller running Cr50 firmware provides several
> +functions, including TPM-like functionality. It communicates over
> +SPI using the FIFO protocol described in the PTP Spec, section 6.
> +
> +Required properties:
> +- compatible: Should be "google,cr50".
> +- spi-max-frequency: Maximum SPI frequency.
> +
> +Optional properties:
> +- access-delay-ms: Required delay between subsequent transactions on SPI.

As I mentioned, there may be common properties. It doesn't seem you 
looked, so I did:

- spi-rx-delay-us  - (optional) Microsecond delay after a read transfer.
- spi-tx-delay-us  - (optional) Microsecond delay after a write transfer.

Seems to me setting one or both of these should work for you.

> +- sleep-delay-ms: Time after the last SPI activity, after which the chip
> +  may go to sleep.
> +- wake-start-delay-ms: Time after initiating wake up before the chip is
> +  ready to accept commands over SPI.

I also asked why these 2 can't be hard-coded in the driver?

> +
> +Example:
> +
> + {
> +status = "okay";
> +
> +cr50@0 {
> +compatible = "google,cr50";
> +reg = <0>;
> +spi-max-frequency = <80>;
> +
> +access-delay-ms = <2>;
> +sleep-delay-ms = <1000>;
> +wake-start-delay-ms = <60>;
> +};
> +};
> -- 
> 2.6.6
> 

Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50

[Rob Herring]

On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote:
> Add TPM2.0 PTP FIFO compatible SPI interface for chips with Cr50
> firmware. Several timing-related properties that may differ from
> one firmware version to another are added to devicetree.
> Document these properties.
> 
> Signed-off-by: Andrey Pronin 
> ---
>  .../devicetree/bindings/security/tpm/cr50_spi.txt  | 32 
> ++
>  1 file changed, 32 insertions(+)
>  create mode 100644 
> Documentation/devicetree/bindings/security/tpm/cr50_spi.txt
> 
> diff --git a/Documentation/devicetree/bindings/security/tpm/cr50_spi.txt 
> b/Documentation/devicetree/bindings/security/tpm/cr50_spi.txt
> new file mode 100644
> index 000..f212b6b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/security/tpm/cr50_spi.txt
> @@ -0,0 +1,32 @@
> +* H1 Secure Microcontroller with Cr50 Firmware on SPI Bus.
> +
> +H1 Secure Microcontroller running Cr50 firmware provides several
> +functions, including TPM-like functionality. It communicates over
> +SPI using the FIFO protocol described in the PTP Spec, section 6.
> +
> +Required properties:
> +- compatible: Should be "google,cr50".
> +- spi-max-frequency: Maximum SPI frequency.
> +
> +Optional properties:
> +- access-delay-ms: Required delay between subsequent transactions on SPI.

As I mentioned, there may be common properties. It doesn't seem you 
looked, so I did:

- spi-rx-delay-us  - (optional) Microsecond delay after a read transfer.
- spi-tx-delay-us  - (optional) Microsecond delay after a write transfer.

Seems to me setting one or both of these should work for you.

> +- sleep-delay-ms: Time after the last SPI activity, after which the chip
> +  may go to sleep.
> +- wake-start-delay-ms: Time after initiating wake up before the chip is
> +  ready to accept commands over SPI.

I also asked why these 2 can't be hard-coded in the driver?

> +
> +Example:
> +
> + {
> +status = "okay";
> +
> +cr50@0 {
> +compatible = "google,cr50";
> +reg = <0>;
> +spi-max-frequency = <80>;
> +
> +access-delay-ms = <2>;
> +sleep-delay-ms = <1000>;
> +wake-start-delay-ms = <60>;
> +};
> +};
> -- 
> 2.6.6
>