Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230517223007.178432-1-boerge.struempfel@gmail.com>
In-Reply-To: <20230517223007.178432-1-boerge.struempfel@gmail.com>
From:   Fabio Estevam <festevam@gmail.com>
Date:   Wed, 17 May 2023 19:43:41 -0300
Message-ID: <CAOMZO5CqMMCCOsAB3YgJUUampE=iZru57d=qoX13-GkSaaC5gg@mail.gmail.com>
Subject: Re: [PATCH v4 1/3] spi: add SPI_MOSI_IDLE_LOW mode bit
To:     Boerge Struempfel <boerge.struempfel@gmail.com>
Cc:     bstruempfel@ultratronik.de, andy.shevchenko@gmail.com,
        amit.kumar-mahapatra@amd.com, broonie@kernel.org,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        NXP Linux Team <linux-imx@nxp.com>,
        linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Wed, May 17, 2023 at 7:30=E2=80=AFPM Boerge Struempfel
<boerge.struempfel@gmail.com> wrote:
>
> Some spi controller switch the mosi line to high, whenever they are
> idle. This may not be desired in all use cases. For example neopixel
> leds can get confused and flicker due to misinterpreting the idle state.
> Therefore, we introduce a new spi-mode bit, with which the idle behaviour
> can be overwritten on a per device basis.
>
> Signed-off-by: Boerge Struempfel <boerge.struempfel@gmail.com>
>
>
> Link for versions:
>   v1 and v2: https://lore.kernel.org/linux-spi/20230511135632.78344-1-bst=
ruempfel@ultratronik.de/
>   v3: https://lore.kernel.org/linux-spi/20230517103007.26287-1-boerge.str=
uempfel@gmail.com/T/#t
>
> Changes from V3:
>   - Added missing paranthesis which caused builderrors
>
> Changes from V2:
>   - Removed the device-tree binding since this should not be managed by
>     the DT but by the device itself.
>   - Replaced all occurences of spi->chip_select with the corresponding
>     macro spi_get_chipselect(spi,0)
>
> Changes from V1:
>   - Added patch, introducing the new devicetree binding flag
>   - Split the generic spi part of the patch from the imx-spi specific
>     part
>   - Replaced SPI_CPOL and SPI_CPHA by the combined SPI_MODE_X_MASK bit
>     in the imx-spi.c modebits.
>   - Added the SPI_MOSI_IDLE_LOW bit to spidev

The change log should be placed below the --- line.

> ---
>  include/uapi/linux/spi/spi.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/spi/spi.h b/include/uapi/linux/spi/spi.h
> index 9d5f58059703..ca56e477d161 100644
> --- a/include/uapi/linux/spi/spi.h
> +++ b/include/uapi/linux/spi/spi.h
> @@ -28,6 +28,7 @@
>  #define        SPI_RX_OCTAL            _BITUL(14)      /* receive with 8=
 wires */
>  #define        SPI_3WIRE_HIZ           _BITUL(15)      /* high impedance=
 turnaround */
>  #define        SPI_RX_CPHA_FLIP        _BITUL(16)      /* flip CPHA on R=
x only xfer */
> +#define SPI_MOSI_IDLE_LOW      _BITUL(17)      /* leave mosi line low wh=
en idle */

Should tools/spi/spidev_test.c be changed to include this new
mosi-idle-low option?