From mboxrd@z Thu Jan 1 00:00:00 1970 From: s.hauer@pengutronix.de (Sascha Hauer) Date: Wed, 15 Dec 2010 22:55:55 +0100 Subject: IMX SPI - 17-24 bit bug and >32 bit support. In-Reply-To: References: Message-ID: <20101215215555.GF29833@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Dec 15, 2010 at 04:33:54PM -0500, Bill Pringlemeir wrote: > > Attach is an example patch to the spi_imx.c file. The iMX spi doesn't > handle 17-24bit values properly. At least in sound/soc, the 24 bit > values are being passed with three data bytes per unit. Also the SPI > count is being filled with '3' as a length. Such data passed to the > current iMX spi driver will cause it to loop forever as it decrements > the unsigned length by '4' and eventually accesses invalid memory. > > I believe that the reset of the kernel believes that the SPI layer > should use three bytes per transfer/receive item if the SPI word > length is 17 to 24 bits. I remember soneone mentioned this already. Patches for this are welcome. > > The other issue is that the current driver does not support SPI > transfers of greater than 32bits (called 'BURST LENGTH' in iMX > documentation). The support for transfers > 32 bit is arguably broken at least on the older cspi cores. That's why the we have the following comment next to the spi platform data: /* * struct spi_imx_master - device.platform_data for SPI controller devices. * @chipselect: Array of chipselects for this master. Numbers >= 0 mean gpio * pins, numbers < 0 mean internal CSPI chipselects according * to MXC_SPI_CS(). Normally you want to use gpio based chip * selects as the CSPI module tries to be intelligent about * when to assert the chipselect: The CSPI module deasserts the * chipselect once it runs out of input data. The other problem * is that it is not possible to mix between high active and low * active chipselects on one single bus using the internal * chipselects. Unfortunately Freescale decided to put some * chipselects on dedicated pins which are not usable as gpios, * so we have to support the internal chipselects. * @num_chipselect: ARRAY_SIZE(chipselect) */ Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |