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Message-ID: <21d3314355b43ecd6acc42f9dfedec501418332d.camel@gmail.com>
Subject: Re: [PATCH v3 1/6] spi: Add SPI mode bit for MOSI idle state
 configuration
From: Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To: Marcelo Schmitt <marcelo.schmitt@analog.com>, broonie@kernel.org, 
 lars@metafoo.de, Michael.Hennerich@analog.com, jic23@kernel.org, 
 robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
  nuno.sa@analog.com, dlechner@baylibre.com, marcelo.schmitt1@gmail.com
Cc: linux-iio@vger.kernel.org, devicetree@vger.kernel.org, 
	linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org
Date: Wed, 05 Jun 2024 11:14:33 +0200
In-Reply-To: <e1d5d57f7a7481c84f64a764f9898122e278739b.1717539384.git.marcelo.schmitt@analog.com>
References: <cover.1717539384.git.marcelo.schmitt@analog.com>
	 <e1d5d57f7a7481c84f64a764f9898122e278739b.1717539384.git.marcelo.schmitt@analog.com>
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On Tue, 2024-06-04 at 19:41 -0300, Marcelo Schmitt wrote:
> The behavior of an SPI controller data output line (SDO or MOSI or COPI
> (Controller Output Peripheral Input) for disambiguation) is not specified
> when the controller is not clocking out data on SCLK edges. However, ther=
e
> exist SPI peripherals that require specific COPI line state when data is
> not being clocked out of the controller.
> Add SPI mode bit to allow pheripherals to request explicit COPI idle
> behavior when needed.
>=20
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> ---
> =C2=A0drivers/spi/spi.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 | 6 ++++++
> =C2=A0include/uapi/linux/spi/spi.h | 3 ++-
> =C2=A02 files changed, 8 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 289feccca376..6072b6e93bef 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -3921,6 +3921,12 @@ int spi_setup(struct spi_device *spi)
> =C2=A0		(SPI_TX_DUAL | SPI_TX_QUAD | SPI_TX_OCTAL |
> =C2=A0		 SPI_RX_DUAL | SPI_RX_QUAD | SPI_RX_OCTAL)))
> =C2=A0		return -EINVAL;
> +	/* Check against conflicting MOSI idle configuration */
> +	if ((spi->mode & SPI_MOSI_IDLE_LOW) && (spi->mode &
> SPI_MOSI_IDLE_HIGH)) {
> +		dev_warn(&spi->dev,
> +			 "setup: erratic MOSI idle configuration. Set to idle
> low\n");
> +		spi->mode &=3D ~SPI_MOSI_IDLE_HIGH;
> +	}

Should we assume such a thing? IOW, should this be treated as a warning or =
a
real error? I would assume this should be a configuration error and return =
-
EINVAL but...

- Nuno S=C3=A1