by Tomas Winkler

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Subject: RE: [tpmdd-devel] [PATCH 2/4] tmp/tpm_crb: fix Intel PTT hw bug during idle state

>
> > Subject: Re: [PATCH 2/4] tmp/tpm_crb: fix Intel PTT hw bug during idle
> > state
> >
> > On Sat, Oct 08, 2016 at 04:56:39PM +0000, Winkler, Tomas wrote:
> > >
> > > >
> > > > On Sat, Oct 08, 2016 at 02:27:06PM +0000, Winkler, Tomas wrote:
> > > > > >
> > > > > > On Sat, Oct 08, 2016 at 02:59:37PM +0300, Tomas Winkler wrote:
> > > > > > > From: "Winkler, Tomas" <[email protected]>
> > > > > > >
> > > > > > > There is a HW bug in Skylake, Kabylake, and Broxton PCH
> > > > > > > Intel PTT device, where most of the registers in the control
> > > > > > > area except START, REQUEST, CANCEL, and LOC_CTRL lost
> > > > > > > retention when the device is in the
> > > > > > idle state.
> > > > > > > Hence we need to bring the device to ready state before
> > > > > > > accessing the other registers. The fix brings device to
> > > > > > > ready state before trying to read command and response
> > > > > > > buffer addresses in order to remap the for
> > > > > > access.
> > > > > > >
> > > > > > > Signed-off-by: Tomas Winkler <[email protected]>
> > > > > > > ---
> > > > > > > V2: cmd read need to be called also before crb_init as this
> > > > > > > will run self test.
> > > > > > > V3: resend.
> > > > > > > V4: add Kabylake to the list of effected platforms
> > > > > > >
> > > > > > > drivers/char/tpm/tpm_crb.c | 47
> > > > > > > ++++++++++++++++++++++++++++++++++++++--------
> > > > > > > 1 file changed, 39 insertions(+), 8 deletions(-)
> > > > > > >
> > > > > > > diff --git a/drivers/char/tpm/tpm_crb.c
> > > > > > > b/drivers/char/tpm/tpm_crb.c index
> > > > > > > 0f3b3f3d12d3..4eb96b85c653
> > > > > > > 100644
> > > > > > > --- a/drivers/char/tpm/tpm_crb.c
> > > > > > > +++ b/drivers/char/tpm/tpm_crb.c
> > > > > > > @@ -319,6 +319,7 @@ static int crb_map_io(struct acpi_device
> > > > > > > *device,
> > > > > > struct crb_priv *priv,
> > > > > > > struct list_head resources;
> > > > > > > struct resource io_res;
> > > > > > > struct device *dev = &device->dev;
> > > > > > > + u32 pa_high, pa_low;
> > > > > > > u64 cmd_pa;
> > > > > > > u32 cmd_size;
> > > > > > > u64 rsp_pa;
> > > > > > > @@ -346,12 +347,27 @@ static int crb_map_io(struct
> > > > > > > acpi_device *device,
> > > > > > struct crb_priv *priv,
> > > > > > > if (IS_ERR(priv->cca))
> > > > > > > return PTR_ERR(priv->cca);
> > > > > > >
> > > > > > > - cmd_pa = ((u64) ioread32(&priv->cca->cmd_pa_high) << 32) |
> > > > > > > - (u64) ioread32(&priv->cca->cmd_pa_low);
> > > > > > > + /*
> > > > > > > + * PTT HW bug w/a: wake up the device to access
> > > > > > > + * possibly not retained registers.
> > > > > > > + */
> > > > > > > + ret = crb_cmd_ready(dev, priv);
> > > > > > > + if (ret)
> > > > > > > + return ret;
> > > > > > > +
> > > > > > > + pa_high = ioread32(&priv->cca->cmd_pa_high);
> > > > > > > + pa_low = ioread32(&priv->cca->cmd_pa_low);
> > > > > > > + cmd_pa = ((u64)pa_high << 32) | pa_low;
> > > > > > > cmd_size = ioread32(&priv->cca->cmd_size);
> > > > > > > +
> > > > > > > + dev_dbg(dev, "cmd_hi = %X cmd_low = %X cmd_size %X\n",
> > > > > > > + pa_high, pa_low, cmd_size);
> > > > > > > +
> > > > > > > priv->cmd = crb_map_res(dev, priv, &io_res, cmd_pa,
> > cmd_size);
> > > > > > > - if (IS_ERR(priv->cmd))
> > > > > > > - return PTR_ERR(priv->cmd);
> > > > > > > + if (IS_ERR(priv->cmd)) {
> > > > > > > + ret = PTR_ERR(priv->cmd);
> > > > > > > + goto out;
> > > > > > > + }
> > > > > > >
> > > > > > > memcpy_fromio(&rsp_pa, &priv->cca->rsp_pa, 8);
> > > > > > > rsp_pa = le64_to_cpu(rsp_pa); @@ -359,7 +375,8 @@ static
> > int
> > > > > > > crb_map_io(struct acpi_device *device, struct crb_priv
> > > > > > > *priv,
> > > > > > >
> > > > > > > if (cmd_pa != rsp_pa) {
> > > > > > > priv->rsp = crb_map_res(dev, priv, &io_res, rsp_pa,
> > rsp_size);
> > > > > > > - return PTR_ERR_OR_ZERO(priv->rsp);
> > > > > > > + ret = PTR_ERR_OR_ZERO(priv->rsp);
> > > > > > > + goto out;
> > > > > > > }
> > > > > > >
> > > > > > > /* According to the PTP specification, overlapping command
> > > > > > > and response @@ -367,12 +384,18 @@ static int
> > > > > > > crb_map_io(struct acpi_device
> > > > > > *device, struct crb_priv *priv,
> > > > > > > */
> > > > > > > if (cmd_size != rsp_size) {
> > > > > > > dev_err(dev, FW_BUG "overlapping command and
> > response
> > > > > > buffer sizes are not identical");
> > > > > > > - return -EINVAL;
> > > > > > > + ret = -EINVAL;
> > > > > > > + goto out;
> > > > > > > }
> > > > > > > +
> > > > > > > priv->cmd_size = cmd_size;
> > > > > > >
> > > > > > > priv->rsp = priv->cmd;
> > > > > > > - return 0;
> > > > > > > +
> > > > > > > +out:
> > > > > > > + crb_go_idle(dev, priv);
> > > > > > > +
> > > > > > > + return ret;
> > > > > > > }
> > > > > > >
> > > > > > > static int crb_acpi_add(struct acpi_device *device) @@
> > > > > > > -416,7
> > > > > > > +439,15 @@ static int crb_acpi_add(struct acpi_device
> > > > > > > +*device)
> > > > > > > if (rc)
> > > > > > > return rc;
> > > > > > >
> > > > > > > - return crb_init(device, priv);
> > > > > > > + rc = crb_cmd_ready(dev, priv);
> > > > > > > + if (rc)
> > > > > > > + return rc;
> > > > > >
> > > > > > I cannot find any valid reason why crb_map_io calls
> > > > > > crb_go_idle in the except in the case of a failure. This is
> > > > > > something I complained
> > earlier.
> > > > >
> > > > > Haven't I've already explained that? Each flow has to be
> > > > > enclosed by cmdReady and goIdle. There is nothing different
> > > > > here from the other flows in that matter. The assumption here
> > > > > is that we are starting in the idle state bug because of the HW
> > > > > bug we cannot access the registers. So the whole w/o is enclosed
> > > > > in the crb_map_io. After that we are starting from new, from the idle
> state.
> > > >
> > > > But why you have to do crb_go_idle upon returning from crb_map_io()?
> > >
> > > As written above it's is closed code... cmdReady <perform the task>
> goIdle.
> >
> > It does extra cmdReady/goIdle. I don't really get your explanation here.
> > crb_map_io() is not a utility function used after the driver has initialized.
> >
> > crb_map_io() could just leave it ready so you don't have to do an
> > explicit call to crb_cmd_ready() in crb_acpi_add. I think this is quite obvious.
> >
> > > >
> > > > > > A minor thing but the extra crb_cmd_ready is basically clutter
> > > > > > to the initialization.
> > > > >
> > > > > The extra cmdReady is here in case runtime pm is not compiled
> > > > > into the kernel and assumption here is that we are starting in the idle
> state.
> > > > > Please remember that unfortunately we cannot detect whether we
> > > > > are in ready on idle state as the status register is not
> > > > > retained, so everything has to be ordered properly.
> > > >
> > > > Rather you it would be better not to use cmdReady/goIdle at all if
> > > > kernel is not compiled with CONFIG_PM.
> > >
> > > ????. You have to do the initial cmdReady, and that's what the code
> > > does, otherwise your driver won't work at all. CONFIG_PM is the
> > > software thing, it doesn't magically match the HW power state. So
> > > you need to do cmdReady.
> >
> > In every machine that I've tried so far the PTT has worked if
> > cmdReady/goIdle haven't been used at all by the OS during a power cycle.
>
> You mean BXT and SKL, right, but that's because you've been blessed with a
> specific BIOS that keeps it up.

Hmm, now I understand why you have a bit different angle on the problem.
Tomas