From: "FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu)" <fixed-term.Konstantin.Buecheler@escrypt•com>
To: "linux-can@vger•kernel.org" <linux-can@vger•kernel.org>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>
Cc: Dan Murphy <dmurphy@ti•com>
Subject: can: tcan4x5x: spi bits_per_word issue on Raspberry PI
Date: Wed, 14 Aug 2019 15:01:44 +0000 [thread overview]
Message-ID: <3f71bdff8f4f4fe19ad9a09be89bc73d@escrypt.com> (raw)
> Hi all,
>
> I am trying to use a tcan4550 together with a Raspberry PI 3 B. I am using the
> tcan4x5x driver from net-next.
> I always get the following error during startup.
> tcan4x5x spi0.0: Probe failed, err=-22
> tcan4x5x: probe of spi0.0 failed with error -22
>
> I realized that this happens because the Raspberry PI does only support 8/9 bit
> words. https://elinux.org/index.php?title=RPi_SPI#Supported_bits_per_word
> In the driver it is set to 32.
> spi->bits_per_word = 32;
>
> Setting this to 8 does not help of course since the tcan chip expects a multiple of
> 32 per spi transaction.
> I don't know if this is a Raspberry Pi specific problem or if there are more devices
> with this hardware limitation.
>
> Does anyone have a workaround for that?
It seems to be enough to just change the bits_per_word value to 8
>
> If this a common issue it might be a good idea to patch the driver. I will check if I
> can find proper a way to do so.
>
> Regards,
> Konstantin
Now I have another really confusing problem. Anything I write to SPI is written little endian. The tcan chip expects big endian.
Anything I read from SPI is treated as little endian but is big endian. Does anyone know why this happens?
Is there a flag or something I can set for the SPI device/wire to fix this?
Regards,
Konstantin
next reply other threads:[~2019-08-14 15:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 15:01 FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu) [this message]
2019-08-15 8:34 ` can: tcan4x5x: spi bits_per_word issue on Raspberry PI Marc Kleine-Budde
[not found] ` <e6577cc2-89fc-9428-b73e-47f41eff2949@posteo.de>
2019-08-16 8:26 ` AW: " FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu)
2019-08-16 8:37 ` Marc Kleine-Budde
-- strict thread matches above, loose matches on Subject: below --
2019-08-14 9:43 FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu)
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