From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Kleine-Budde Subject: Re: [PATCH] can: mcp251x: convert to half-duplex SPI Date: Tue, 25 Feb 2020 22:43:07 +0100 Message-ID: <0ac77abd-0df5-e437-ea46-f6c77f59b81c@pengutronix.de> References: <1582655734-20890-1-git-send-email-tharvey@gateworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from metis.ext.pengutronix.de ([85.220.165.71]:58733 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728756AbgBYVnO (ORCPT ); Tue, 25 Feb 2020 16:43:14 -0500 In-Reply-To: <1582655734-20890-1-git-send-email-tharvey@gateworks.com> Content-Language: de-DE Sender: linux-can-owner@vger.kernel.org List-ID: To: Tim Harvey , linux-kernel@vger.kernel.org, linux-can@vger.kernel.org, Wolfgang Grandegger Cc: =?UTF-8?Q?Timo_Schl=c3=bc=c3=9fler?= , Andy Shevchenko On 2/25/20 7:35 PM, Tim Harvey wrote: > Some SPI host controllers such as the Cavium Thunder do not support > full-duplex SPI. Using half-duplex transfers allows the driver to work > with those host controllers. There are several transfers left in the driver, where both rx_buf and tx_buf are set. How does your host controller driver know which one to handle? Marc > Signed-off-by: Tim Harvey > --- > drivers/net/can/spi/mcp251x.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c > index 5009ff2..840c31c 100644 > --- a/drivers/net/can/spi/mcp251x.c > +++ b/drivers/net/can/spi/mcp251x.c > @@ -290,23 +290,23 @@ static u8 mcp251x_read_reg(struct spi_device *spi, u8 reg) > priv->spi_tx_buf[0] = INSTRUCTION_READ; > priv->spi_tx_buf[1] = reg; > > - mcp251x_spi_trans(spi, 3); > - val = priv->spi_rx_buf[2]; > + spi_write_then_read(spi, priv->spi_tx_buf, 2, &val, 1); > > return val; > } > > static void mcp251x_read_2regs(struct spi_device *spi, u8 reg, u8 *v1, u8 *v2) > { > + u8 val[4] = {0}; > struct mcp251x_priv *priv = spi_get_drvdata(spi); > > priv->spi_tx_buf[0] = INSTRUCTION_READ; > priv->spi_tx_buf[1] = reg; > > - mcp251x_spi_trans(spi, 4); > + spi_write_then_read(spi, priv->spi_tx_buf, 2, val, 2); > > - *v1 = priv->spi_rx_buf[2]; > - *v2 = priv->spi_rx_buf[3]; > + *v1 = val[0]; > + *v2 = val[1]; > } > > static void mcp251x_write_reg(struct spi_device *spi, u8 reg, u8 val) > Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |