linux-kernel - Re: [Patch V8 2/3] tpm_tis-spi: Add hardware wait polling

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Date:   Sun, 19 Mar 2023 15:42:32 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Krishna Yarlagadda <kyarlagadda@...dia.com>
Cc:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "peterhuewe@....de" <peterhuewe@....de>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Sowjanya Komatineni <skomatineni@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>
Subject: Re: [Patch V8 2/3] tpm_tis-spi: Add hardware wait polling

On Wed, Mar 15, 2023 at 03:47:33PM +0000, Krishna Yarlagadda wrote:
> 
> > -----Original Message-----
> > From: Jarkko Sakkinen <jarkko@...nel.org>
> > Sent: 12 March 2023 03:19
> > To: Krishna Yarlagadda <kyarlagadda@...dia.com>; robh+dt@...nel.org;
> > broonie@...nel.org; peterhuewe@....de; jgg@...pe.ca;
> > krzysztof.kozlowski+dt@...aro.org; linux-spi@...r.kernel.org; linux-
> > tegra@...r.kernel.org; linux-integrity@...r.kernel.org; linux-
> > kernel@...r.kernel.org
> > Cc: thierry.reding@...il.com; Jonathan Hunter <jonathanh@...dia.com>;
> > Sowjanya Komatineni <skomatineni@...dia.com>; Laxman Dewangan
> > <ldewangan@...dia.com>
> > Subject: Re: [Patch V8 2/3] tpm_tis-spi: Add hardware wait polling
> > 
> > External email: Use caution opening links or attachments
> > 
> > 
> > On Thu, 2023-03-02 at 09:48 +0530, Krishna Yarlagadda wrote:
> > > +int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16
> > > len,
> > > +                        u8 *in, const u8 *out)
> > > +{
> > > +       struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
> > > +       struct spi_controller *ctlr = phy->spi_device->controller;
> > > +
> > > +       /*
> > > +        * TPM flow control over SPI requires full duplex support.
> > > +        * Send entire message to a half duplex controller to handle
> > > +        * wait polling in controller.
> > > +        * Set TPM HW flow control flag..
> > > +        */
> > > +       if (ctlr->flags & SPI_CONTROLLER_HALF_DUPLEX)
> > > +               return tpm_tis_spi_hw_flow_transfer(data, addr, len,
> > > in,
> > > +                                                   out);
> > > +       else
> > > +               return tpm_tis_spi_sw_flow_transfer(data, addr, len,
> > > in,
> > > +                                                   out);
> > > +}
> > > +
> > 
> > Based on the condition, better names would be
> Though condition is based on half duplex, functions are implementing
> HW or SW flow of the transfer.

Both are hardwaw flows in the sense that you are controlling a piece of hardware.

BR, Jarkko