linux-kernel - Re: [PATCH 1/3] tpm_crb: map locality registers

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Date:   Tue, 11 Oct 2016 21:21:00 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>, g@...el.com
Cc:     Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        "moderated list:TPM DEVICE DRIVER" 
        <tpmdd-devel@...ts.sourceforge.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] tpm_crb: map locality registers

On Tue, Oct 11, 2016 at 11:01:43AM -0600, Jason Gunthorpe wrote:
> On Tue, Oct 11, 2016 at 12:23:04PM +0300, Jarkko Sakkinen wrote:
> > In order to provide access to locality registers, this commits adds
> > mapping of the head of the CRB registers, which are located right
> > before the control area.
> 
> I think you should squash this into the prior patch, no sense in
> changing all these lines twice
> 
> But looks better to me.

So... do you suggest to squash with request/reliquish locality stuff?
Just checking because this is 1/3 :)

> > -	priv->cca = crb_map_res(dev, priv, &io_res, buf->control_address,
> > -				sizeof(struct crb_control_area));
> > -	if (IS_ERR(priv->cca))
> > -		return PTR_ERR(priv->cca);
> > +	if (priv->flags & CRB_FL_CRB_START) {
> > +		priv->regs_h = crb_map_res(dev, priv, &io_res, io_res.start,
> > +					   sizeof(struct crb_regs_head));
> > +		if (IS_ERR(priv->regs_h))
> > +			return PTR_ERR(priv->regs_h);
> > +	}
> > +
> > +	priv->regs_t = crb_map_res(dev, priv, &io_res, buf->control_address,
> > +				   sizeof(struct crb_regs_tail));
> > +	if (IS_ERR(priv->regs_t))
> > +		return PTR_ERR(priv->regs_t);
> 
> So.. The ACPI IO region starts at the head area and continues to
> include the control area, as one nice sane region - except for some
> older stuff that puts the control area outside the ACPI IO region?

Yes. The old hardware triggered SMM to do a DMA transfer (those that
so called ACPI start). As a workaround for some of the hardware the
driver always sets the CRB start flag also in the control area.

That's why I also propose that we replace them with a single flag.

> That makes a lot more sense..
> 
> Maybe chuck in a
> 
>    if (priv->flags & CRB_FL_CRB_START) {
>       if (buf->control_address != io_res.start + sizeof(struct
>           crb_regs_head))
>           dev_warn(dev, FIRMWARE_BUG "Bad ACPI memory layout")
> 
> Jason

As a sanity check this would probably make sense.


/Jarkko