linux-kernel - Re: [PATCH v1 1/2] spi: npcm-pspi: add full duplex support

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Message-ID: <Yt6JSm3vrkdkvSpo@sirena.org.uk>
Date:   Mon, 25 Jul 2022 13:15:06 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Tomer Maimon <tmaimon77@...il.com>
Cc:     Avi Fishman <avifishman70@...il.com>,
        Tali Perry <tali.perry1@...il.com>,
        Joel Stanley <joel@....id.au>,
        Patrick Venture <venture@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        linux-spi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH v1 1/2] spi: npcm-pspi: add full duplex support

On Sun, Jul 24, 2022 at 12:35:37PM +0300, Tomer Maimon wrote:
> On Thu, 21 Jul 2022 at 16:46, Mark Brown <broonie@...nel.org> wrote:
> > On Thu, Jul 21, 2022 at 01:15:55PM +0300, Tomer Maimon wrote:

> > > This patch adds full duplex support for NPCM PSPI driver by storing all
> > > rx-data when the Rx-buffer is defined also for TX-buffer handling.

> > This doesn't seem to entirely correspond to what the patch does, nor to
> > what the driver currently does?  I can't see any dummy read code in the
> > current driver.

> In the current handler file, in the handler function.
> static irqreturn_t npcm_pspi_handler(int irq, void *dev_id)

> -       if (priv->tx_buf) {
> -               if (stat & NPCM_PSPI_STAT_RBF) {
> -                       ioread8(NPCM_PSPI_DATA + priv->base);

> the read above doing a dummy read

That's reading a single byte, not an entire buffer, and from a quick
glance looks more like an ack.  Though perhaps you just end up with a
lot of interrupts and do that anyway.

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