linux-kernel - Re: [PATCH v4 3/8] spi: stm32: Add 'SPI_SIMPLEX_RX', 'SPI_3WIRE

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Date:   Sat, 23 May 2020 09:35:06 +0800
From:   dillon min <dillon.minfei@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>, p.zabel@...gutronix.de,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Alexandre Torgue <alexandre.torgue@...com>,
        thierry.reding@...il.com, Sam Ravnborg <sam@...nborg.org>,
        Dave Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v4 3/8] spi: stm32: Add 'SPI_SIMPLEX_RX', 'SPI_3WIRE_RX'
 support for stm32f4

On Sat, May 23, 2020 at 12:29 AM Mark Brown <broonie@...nel.org> wrote:
>
> On Fri, May 22, 2020 at 11:59:25PM +0800, dillon min wrote:
>
> > but, after spi-core create a dummy tx_buf or rx_buf, then i can't get
> > the correct spi_3wire direction.
> > actually, this dummy tx_buf is useless for SPI_3WIRE. it's has meaning
> > for SPI_SIMPLE_RX mode,
> > simulate SPI_FULL_DUMPLEX
>
> Oh, that's annoying.  I think the fix here is in the core, it should
> ignore MUST_TX and MUST_RX in 3WIRE mode since they clearly make no
> sense there.

How about add below changes to spi-core

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 8994545..bfd465c 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1022,7 +1022,8 @@ static int spi_map_msg(struct spi_controller
*ctlr, struct spi_message *msg)
        void *tmp;
        unsigned int max_tx, max_rx;

-       if (ctlr->flags & (SPI_CONTROLLER_MUST_RX | SPI_CONTROLLER_MUST_TX)) {
+       if ((ctlr->flags & (SPI_CONTROLLER_MUST_RX | SPI_CONTROLLER_MUST_TX)) &&
+               !(msg->spi->mode & SPI_3WIRE)) {
                max_tx = 0;
                max_rx = 0;

for my board, lcd panel ilitek ill9341 use 3wire mode, gyro l3gd20 use
simplex rx mode.
it's has benefits to l3gd20, no impact to ili9341.

if it's fine to spi-core, i will include it to my next submits.

thanks

best regards.

Dillon