linux-kernel - Re: [PATCH 0/2] tpm: add driver for cr50 on SPI

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Message-ID: <20160715171557.GC109276@apronin>
Date:	Fri, 15 Jul 2016 10:15:57 -0700
From:	Andrey Pronin <apronin@...omium.org>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Peter Huewe <peterhuewe@....de>,
	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Marcel Selhorst <tpmdd@...horst.net>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	groeck@...omium.org, smbarber@...omium.org, dianders@...omium.org
Subject: Re: [PATCH 0/2] tpm: add driver for cr50 on SPI

On Thu, Jul 14, 2016 at 09:28:14PM -0600, Jason Gunthorpe wrote:
> On Thu, Jul 14, 2016 at 07:50:26PM -0700, Andrey Pronin wrote:
> > Yes, it has a TCG-compliant interface, however, there are several things
> > specific to this device:
> >  - need to ensure a certain delay between spi transactions, or else
> >    the chip can miss several first bytes.
> >  - if there is no spi activity for this chip, it may go to sleep, and
> >    needs to be waken up before sending further commands.
> >  - it has some vendor-specific registers accessible from spi bus.
> 
> This all needs to be commented clearly in the driver..
> 

Will provide more details in the patch description. The driver code
has comments about those cases in the code: see cr50_ensure_access_delay
and cr50_needs_waking, for example.