Re: [tpmdd-devel] [PATCH 3/3] tpm, tpm_crb: runtime power management

[Tomas Winkler]

On Thu, Jun 16, 2016 at 10:57 PM, Jarkko Sakkinen
<jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
> Hi Thomas,
>
> I'm on a vacation this week but I'll give you quick answers :)
>
> On Tue, Jun 14, 2016 at 04:14:58PM +0300, Tomas Winkler wrote:
>> On Wed, Jun 8, 2016 at 2:02 AM, Jarkko Sakkinen
>> <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
>> > The register TPM_CRB_CTRL_REQ_0 contains bits goIdle and cmdReady for
>> > invoking the chip to suspend and resume. This commit implements runtime
>> > PM for tpm_crb by using these bits.
>> >
>> > The legacy ACPI start (SMI + DMA) based devices do not support these
>> > bits. Thus this functionality only is enabled only for CRB start (MMIO)
>> > based devices.
>> >
>> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
>> > ---
>> >  drivers/char/tpm/tpm-interface.c |  3 ++
>> >  drivers/char/tpm/tpm_crb.c       | 62 ++++++++++++++++++++++++++++++++++++++--
>> >  2 files changed, 63 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> > index 5e3c1b6..3b85648 100644
>> > --- a/drivers/char/tpm/tpm-interface.c
>> > +++ b/drivers/char/tpm/tpm-interface.c
>> > @@ -29,6 +29,7 @@
>> >  #include <linux/mutex.h>
>> >  #include <linux/spinlock.h>
>> >  #include <linux/freezer.h>
>> > +#include <linux/pm_runtime.h>
>> >
>> >  #include "tpm.h"
>> >  #include "tpm_eventlog.h"
>> > @@ -350,6 +351,7 @@ ssize_t tpm_transmit(struct tpm_chip *chip, const char *buf,
>> >                 return -E2BIG;
>> >         }
>> >
>> > +       pm_runtime_get_sync(chip->dev.parent);
>> >         mutex_lock(&chip->tpm_mutex);
>> >
>> >         rc = chip->ops->send(chip, (u8 *) buf, count);
>> > @@ -394,6 +396,7 @@ out_recv:
>> >                         "tpm_transmit: tpm_recv: error %zd\n", rc);
>> >  out:
>> >         mutex_unlock(&chip->tpm_mutex);
>> > +       pm_runtime_put_sync(chip->dev.parent);
>> >         return rc;
>> >  }
>> >
>> > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
>> > index ca2cad9..71cc7cd 100644
>> > --- a/drivers/char/tpm/tpm_crb.c
>> > +++ b/drivers/char/tpm/tpm_crb.c
>> > @@ -20,6 +20,7 @@
>> >  #include <linux/rculist.h>
>> >  #include <linux/module.h>
>> >  #include <linux/platform_device.h>
>> > +#include <linux/pm_runtime.h>
>> >  #include "tpm.h"
>> >
>> >  #define ACPI_SIG_TPM2 "TPM2"
>> > @@ -41,7 +42,6 @@ enum crb_ca_request {
>> >
>> >  enum crb_ca_status {
>> >         CRB_CA_STS_ERROR        = BIT(0),
>> > -       CRB_CA_STS_TPM_IDLE     = BIT(1),
>> >  };
>> >
>> >  enum crb_start {
>> > @@ -68,6 +68,8 @@ struct crb_control_area {
>> >
>> >  enum crb_status {
>> >         CRB_STS_COMPLETE        = BIT(0),
>> > +       CRB_STS_READY           = BIT(1),
>> > +       CRB_STS_IDLE            = BIT(2),
>> >  };
>> >
>> >  enum crb_flags {
>> > @@ -81,9 +83,52 @@ struct crb_priv {
>> >         struct crb_control_area __iomem *cca;
>> >         u8 __iomem *cmd;
>> >         u8 __iomem *rsp;
>> > +       wait_queue_head_t idle_queue;
>>
>>
>> I'm failing to find the code that is calling wake_up_interruptible(idle_queue);
>
> Ugh, my bad. This actually should not be declared at all. Will remove it
> from the next version and NULL should be passed to wait_for_tpm_stat()
> as the driver does not yet support interrupts (Haswell did not have
> them, not sure about later gens).
>
>
>> >  };
>> >
>> > -static SIMPLE_DEV_PM_OPS(crb_pm, tpm_pm_suspend, tpm_pm_resume);
>> > +static int __maybe_unused crb_runtime_suspend(struct device *dev)
>> > +{
>> > +       struct tpm_chip *chip = dev_get_drvdata(dev);
>> > +       struct crb_priv *priv = dev_get_drvdata(&chip->dev);
>> > +       u32 req;
>> > +
>> > +       if (priv->flags & CRB_FL_ACPI_START)
>> > +               return 0;
>> > +
>> > +       req = ioread32(&priv->cca->req);
>> > +
>> > +       iowrite32(cpu_to_le32(req | CRB_CA_REQ_GO_IDLE), &priv->cca->req);
>> > +
>> > +       if (wait_for_tpm_stat(chip, CRB_STS_IDLE, chip->timeout_c,
>> > +                             &priv->idle_queue, false))
>> > +               dev_warn(&chip->dev, "idle timed out\n");
>>
>> Unfortunately you cannot do that as there is an HW errata, the status
>> register value might not be defined here during power transition
>> You should poll for request CRB_CA_REQ_GO_IDLE goes to 0 as descried
>> in the spec . only after that you can check for the status register
>> (thought it's maybe not needed)
>
> And I do exactly what you are asking me to do.
>
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static int __maybe_unused crb_runtime_resume(struct device *dev)
>>
>> why this is marked unused, why just not compile it out? if the
>> CONFIG_PM is not set?
>
> It is compiled out if it is unused. Why would you want to trash the code
> with #ifdef cages if they are not necessary? I can add /* CONFIG_PM */
> before the function if that makes it cleaner.

I'm not sure about that, I believe it  just suppresses warnings.
You will need something --gc-sessions int the linker, I'm not sure
this is used by kernel.
>
>> > +{
>> > +       struct tpm_chip *chip = dev_get_drvdata(dev);
>> > +       struct crb_priv *priv = dev_get_drvdata(&chip->dev);
>> > +       u32 req;
>> > +
>> > +       if (priv->flags & CRB_FL_ACPI_START)
>> > +               return 0;
>> > +
>> > +       req = ioread32(&priv->cca->req);
>> > +       iowrite32(cpu_to_le32(req | CRB_CA_REQ_CMD_READY), &priv->cca->req);
>> > +
>> > +       if (wait_for_tpm_stat(chip, CRB_STS_READY, chip->timeout_c,
>> > +                             &priv->idle_queue, false))
>> > +               dev_warn(&chip->dev, "wake timed out\n");
>>
>> Same here,  you should wait for CRB_CA_REQ_CMD_READ to get cleared,
>> only after that it is safe to check the status register.
>
> It does exactly that. I'm not using CRB status register for anything.
>
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static const struct dev_pm_ops crb_pm = {
>> > +       SET_RUNTIME_PM_OPS(crb_runtime_suspend, crb_runtime_resume, NULL)
>> > +       SET_SYSTEM_SLEEP_PM_OPS(tpm_pm_suspend, tpm_pm_resume)
>> > +};
>> >
>> >  static u8 crb_status(struct tpm_chip *chip)
>> >  {
>> > @@ -94,6 +139,14 @@ static u8 crb_status(struct tpm_chip *chip)
>> >             CRB_START_INVOKE)
>> >                 sts |= CRB_STS_COMPLETE;
>> >
>> > +       if ((ioread32(&priv->cca->req) & CRB_CA_REQ_CMD_READY) !=
>> > +           CRB_CA_REQ_CMD_READY)
>> > +               sts |= CRB_STS_READY;
>>
>> There is meaning for checking this w/o the actual transition i.e.
>> setting the before
>
> I'm not sure what you are trying to say.

Sorry, my bad, it should be: There is NO meaning for checking
CRB_CA_REQ_CMD_READY is 0  if this wasn't asserted before, In
interrupt language  it's not edge sensitive not level sensitive

Tomas