From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Chuanhua Han <chuanhua.han@nxp.com>
Cc: "broonie@kernel.org" <broonie@kernel.org>,
"linux-spi@vger.kernel.org" <linux-spi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"eha@deif.com" <eha@deif.com>
Subject: Re: [PATCH 1/2] spi: spi-mem: Add the spi_set_xfer_bpw function
Date: Fri, 28 Sep 2018 09:18:33 +0200 [thread overview]
Message-ID: <20180928091833.15e95f7f@bbrezillon> (raw)
In-Reply-To: <AM6PR04MB43573478FFD0E512A117484097EC0@AM6PR04MB4357.eurprd04.prod.outlook.com>
On Fri, 28 Sep 2018 06:59:58 +0000
Chuanhua Han <chuanhua.han@nxp.com> wrote:
> >
> > It's still unclear why you need to specify a bits_per_word value,
> > but if this is needed, it's probably something you want to add to
> > spi.c, when a message is queued.
> To specify a specific bits_per_word to be able to use the xspi
> (32bit) mode of the fsl_dspi module to transfer data, you can look at
> my PATCH 2/2. Do not add a value in spis.c that takes into account
> that the value assigned to bits_per_word is decided before the
> transfer. Thanks for your check and reply!
I might be wrong, but that's not my understanding of ->bits_per_word.
To me, it's something that you can use when your *device* (not
controller) expects non-byte aligned words [1]. The spi-mem protocol is
definitely designed to work with 1byte large words, so, as I said, I
suspect you're abusing xfer->bits_per_word to address a controller
driver issue.
[1]https://elixir.bootlin.com/linux/latest/source/include/linux/spi/spi.h#L114
next prev parent reply other threads:[~2018-09-28 7:19 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 7:06 [PATCH 1/2] spi: spi-mem: Add the spi_set_xfer_bpw function Chuanhua Han
2018-09-21 7:06 ` [PATCH 2/2] spi: spi-fsl-dspi: Fix support for XSPI transport mode Chuanhua Han
2018-09-28 6:37 ` Chuanhua Han
2018-09-28 6:55 ` Boris Brezillon
2018-09-29 14:56 ` Esben Haabendal
2018-09-29 15:43 ` Boris Brezillon
2018-09-30 2:49 ` Chuanhua Han
2018-09-21 7:06 ` [PATCH] spi: spi-mem: Adjust op len based on message/transfer size limitations Chuanhua Han
2018-09-21 7:15 ` Chuanhua Han
2018-09-28 6:37 ` [PATCH 1/2] spi: spi-mem: Add the spi_set_xfer_bpw function Chuanhua Han
2018-09-28 6:44 ` Boris Brezillon
2018-09-28 6:59 ` Chuanhua Han
2018-09-28 7:18 ` Boris Brezillon [this message]
2018-09-28 7:29 ` Chuanhua Han
2018-09-28 13:26 ` Mark Brown
2018-10-09 9:52 ` Chuanhua Han
2018-10-09 10:05 ` Boris Brezillon
2018-10-09 10:24 ` Chuanhua Han
2018-10-09 11:20 ` Esben Haabendal
2018-10-10 2:42 ` Chuanhua Han
2018-10-10 6:38 ` Esben Haabendal
2018-10-09 10:33 ` Mark Brown
2018-10-09 13:50 ` Esben Haabendal
2018-10-09 10:53 ` Esben Haabendal
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