From: Stefan Wahren <wahrenst@gmx.net>
To: "Nuno Sá" <nuno.sa@analog.com>,
broonie@kernel.org, eric@anholt.net,
"Martin Sperl" <kernel@martin.sperl.org>,
"Lukas Wunner" <lukas@wunner.de>
Cc: f.fainelli@gmail.com, rjui@broadcom.com, sbranden@broadcom.com,
linux-kernel@vger.kernel.org,
bcm-kernel-feedback-list@broadcom.com,
linux-rpi-kernel@lists.infradead.org,
linux-arm-kernel@lists.infradead.org, linux-spi@vger.kernel.org
Subject: Re: [PATCH] spi: spi-bcm2835.c: Fix 3-wire mode
Date: Fri, 28 Jun 2019 17:23:54 +0200 [thread overview]
Message-ID: <1b932c61-982b-aae0-1fef-3c574e7d17eb@gmx.net> (raw)
In-Reply-To: <20190628123023.4696-1-nuno.sa@analog.com>
Hi Nuno,
Am 28.06.19 um 14:30 schrieb Nuno Sá:
> As stated in
> https://www.raspberrypi.org/documentation/hardware/raspberrypi/spi/README.md,
> one of rx or tx buffer's must be null. However, if DMA is enabled, the
> driver sets the SPI_CONTROLLER_MUST_RX | SPI_CONTROLLER_MUST_TX on the
> controller flags. Hence, the spi core will provide dummy buffers even if
> one of the buffers was set to null by the device driver. Thus, the
> communication with the 3-wire device fails.
>
> This patch uses the prepare_message callback to look for the device mode
> and sets/clears the SPI_CONTROLLER_MUST_RX | SPI_CONTROLLER_MUST_TX on a
> per spi message basis. It also assumes that DMA is not supported on
> half-duplex devices.
>
> Signed-off-by: Nuno Sá <nuno.sa@analog.com>
i never tested the 3-wire mode. Could you please describe your test setup?
@Martin, @Lukas Are you fine with this patch?
next prev parent reply other threads:[~2019-06-28 15:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-28 12:30 [PATCH] spi: spi-bcm2835.c: Fix 3-wire mode Nuno Sá
2019-06-28 15:23 ` Stefan Wahren [this message]
2019-06-28 19:00 ` Lukas Wunner
2019-07-01 7:24 ` Sa, Nuno
2019-07-01 11:55 ` Lukas Wunner
2019-07-01 14:21 ` Sa, Nuno
2019-07-03 10:43 ` Lukas Wunner
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