On Sun, 30 Sep 2018 10:18:18 +0000 Chuanhua Han <chuanhua....@nxp.com> wrote:
> > -----Original Message----- > > From: Boris Brezillon <boris.brezil...@bootlin.com> > > Sent: 2018年9月30日 18:04 > > To: Chuanhua Han <chuanhua....@nxp.com> > > Cc: broo...@kernel.org; linux-...@vger.kernel.org; > > linux-kernel@vger.kernel.org; e...@deif.com > > Subject: Re: [PATCH v2 1/4] spi: spi-mem: Add the spi_set_xfer_bpw function > > > > Hi Chuanhua, > > > > On Sun, 30 Sep 2018 17:25:32 +0800 > > Chuanhua Han <chuanhua....@nxp.com> wrote: > > > > > Before we add this spi_transfer to the spi_message chain table, we > > > need bits_per_word_mask based on spi_control to set the bits_per_word > > > of this spi_transfer. > > > > Let's make it clearer: this is wrong. The spi-mem protocol is just using > > bytes, > > not custom size words. Fix the fsl-dspi driver if needed, but don't try to > > adjust > > xfer->bits_per_word in spi-mem.c, because this is inappropriate. > The value of bits_per_word is only known before the spi_message_add_tail > function is called, No, it's not. It's known from the beginning, and spi_setup() defaults to 8 when spidev->bits_per_word is 0, which is exactly what we want. Then, when you send a message through, spi_sync(), spi_validate() makes sure that each transfer in the message has a xfer->bits_per_word != 0 and when that's not the case, it sets it to spi->bits_per_word [2]. Really, there's nothing to fix in spi-mem.c, because it's already doing the right thing (leaving ->bits_per_word to 0 so that it's set to spi->bits_per_word, which should be 8). Maybe we have a bug somewhere else though. [1]https://elixir.bootlin.com/linux/v4.19-rc5/source/drivers/spi/spi.c#L2803 [2]https://elixir.bootlin.com/linux/v4.19-rc5/source/drivers/spi/spi.c#L2869
