lkml.org 
[lkml]   [2023]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [Patch V3 1/3] tpm_tis-spi: Support hardware wait polling
Date
> -----Original Message-----
> From: Mark Brown <broonie@kernel.org>
> Sent: 24 February 2023 00:13
> To: Krishna Yarlagadda <kyarlagadda@nvidia.com>
> Cc: robh+dt@kernel.org; peterhuewe@gmx.de; jgg@ziepe.ca;
> jarkko@kernel.org; krzysztof.kozlowski+dt@linaro.org; linux-
> spi@vger.kernel.org; linux-tegra@vger.kernel.org; linux-
> integrity@vger.kernel.org; linux-kernel@vger.kernel.org;
> thierry.reding@gmail.com; Jonathan Hunter <jonathanh@nvidia.com>;
> Sowjanya Komatineni <skomatineni@nvidia.com>; Laxman Dewangan
> <ldewangan@nvidia.com>
> Subject: Re: [Patch V3 1/3] tpm_tis-spi: Support hardware wait polling
>
> On Thu, Feb 23, 2023 at 06:41:43PM +0000, Krishna Yarlagadda wrote:
>
> > > > + spi_bus_lock(phy->spi_device->master);
> > > > +
> > > > + while (len) {
>
> > > Why?
>
> > TPM supports max 64B in single transaction. Loop to send rest of it.
>
> No, why is there a bus lock?
Bus lock to avoid other clients to be accessed between TPM transfers.

>
> > > > + spi_xfer[0].tx_buf = phy->iobuf;
> > > > + spi_xfer[0].len = 1;
> > > > + spi_message_add_tail(&spi_xfer[0], &m);
> > > > +
> > > > + spi_xfer[1].tx_buf = phy->iobuf + 1;
> > > > + spi_xfer[1].len = 3;
> > > > + spi_message_add_tail(&spi_xfer[1], &m);
>
> > > Why would we make these two separate transfers?
>
> > Tegra QSPI combined sequence requires cmd, addr and data in different
> > transfers. This eliminates need for additional flag for combined sequence.
>
> That needs some documentation, and we might need a flag to ensure the
> core doesn't coalesce the transfers.
Will add comment at top of the function. Bus lock should avoid coalesce of
transfer of single message from others.
KY

\
 
 \ /
  Last update: 2023-03-27 00:34    [W:0.055 / U:0.232 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site