* can: tcan4x5x: spi bits_per_word issue on Raspberry PI
@ 2019-08-14 15:01 FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu)
2019-08-15 8:34 ` Marc Kleine-Budde
0 siblings, 1 reply; 5+ messages in thread
From: FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu) @ 2019-08-14 15:01 UTC (permalink / raw)
To: linux-can, netdev; +Cc: Dan Murphy
> 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
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: can: tcan4x5x: spi bits_per_word issue on Raspberry PI
2019-08-14 15:01 can: tcan4x5x: spi bits_per_word issue on Raspberry PI FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu)
@ 2019-08-15 8:34 ` Marc Kleine-Budde
[not found] ` <e6577cc2-89fc-9428-b73e-47f41eff2949@posteo.de>
0 siblings, 1 reply; 5+ messages in thread
From: Marc Kleine-Budde @ 2019-08-15 8:34 UTC (permalink / raw)
To: FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu), linux-can, netdev
Cc: Dan Murphy
[-- Attachment #1.1: Type: text/plain, Size: 1871 bytes --]
On 8/14/19 5:01 PM, FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu) wrote:
>> 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?
Have you changed the bits_per_word to 8? Then you read just a stream of
bytes. If you tread them as an u32 they are in host order.
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Industrial Linux Solutions | Phone: +49-231-2826-924 |
Vertretung West/Dortmund | Fax: +49-5121-206917-5555 |
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^ permalink raw reply [flat|nested] 5+ messages in thread
* can: tcan4x5x: spi bits_per_word issue on Raspberry PI
@ 2019-08-14 9:43 FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu)
0 siblings, 0 replies; 5+ messages in thread
From: FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu) @ 2019-08-14 9:43 UTC (permalink / raw)
To: linux-can, netdev; +Cc: Dan Murphy
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?
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
^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-08-14 15:01 can: tcan4x5x: spi bits_per_word issue on Raspberry PI FIXED-TERM Buecheler Konstantin (ETAS-SEC/ECT-Mu)
2019-08-15 8:34 ` 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
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