U-CLASS SPI Bus and Devices

[Rudolf J Streif]

Hi Simon,

Thanks for your response.

On 5/7/20 6:36 PM, Simon Glass wrote:
> Hi Rudolf,
>
> On Wed, 18 Mar 2020 at 05:25, Rudolf J Streif <rudolf.streif at ibeeto.com> wrote:
>> I ran into an issue today with a U-CLASS SPI NOR flash device on a NXP
>> FlexSPI controller. U-Boot started correctly from the flash device but
>> using 'sf probe 0:0' would always return 'Invalid bus 0 (err=-19)'. This
>> error message is emitted by spi_get_bus_and_cs() in
>> drivers/spi/spi-uclass.c. I traced the issue to
>> uclass_get_device_by_seq() in drivers/core/uclass.c.
>>
>> The function first searches the device list for a device that already
>> claimed the sequence number (dev->seq). If not found it would look if a
>> device requested that sequence number (dev->seq_req). That would always
>> fail for my device. The bus had not been probed yet and hence dev->seq
>> was -1 and the device also had dev->req_seq set to -1.
>>
>> The board is using a device tree hence it would only make sense to set
>> the requested sequence number via the device tree. However, there is no
>> such thing and even if there was it might not be specified.
>>
>> Consequently, the device was never probed although the driver was
>> correctly set up via device tree.
>>
>> I worked around it by simply setting dev->req_seq of the first device
>> that had it set to -1 to the sequence number the search function was
>> looking for (see patch below). It solved my problem but I don't know if
>> that is the right way of addressing it. I could not find any other
>> solution for this particular problem anywhere.
>>
>> Rudi
> You can put the SPI flash in the device tree with an alias pointing to
> it.. That is the intended way with driver model.

The board I am using the the FSL/NXP LX2160A-RDB. The dts
arch/arm/dts/fsl-lx2160a-rdb.dts defines:

 / {
        model = "NXP Layerscape LX2160ARDB Board";
        compatible = "fsl,lx2160ardb", "fsl,lx2160a";

        aliases {
                spi0 = &fspi;
        };
};

I am I missing something?

Regards,

Rudi


>
> Regards,
> SImon
>
>
>
>>
>>
>> From 0f05ab964fcc7d29d8d467e663d7daa72328cf66 Mon Sep 17 00:00:00 2001
>> From: Rudolf J Streif <rudolf.streif at ibeeto.com>
>> Date: Tue, 17 Mar 2020 17:13:07 -0700
>> Subject: [PATCH] Fix issue with SPI device sequence number
>>
>> If the requested sequence number for a SPI device was -1 (any)
>> then the device would never be probed. This fix simply assigns
>> the sequence number asked for at probing to the device if it has
>> not been probed yet and the requested sequence number is -1.
>>
>> Signed-off-by: Rudolf J Streif <rudolf.streif at ibeeto.com>
>> ---
>>  drivers/core/uclass.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c
>> index fc3157de39..e791103153 100644
>> --- a/drivers/core/uclass.c
>> +++ b/drivers/core/uclass.c
>> @@ -310,6 +310,8 @@ int uclass_find_device_by_seq(enum uclass_id id, int
>> seq_or_req_seq,
>>
>>         uclass_foreach_dev(dev, uc) {
>>                 debug("   - %d %d '%s'\n", dev->req_seq, dev->seq,
>> dev->name);
>> +               if (find_req_seq && dev->req_seq == -1)
>> +                       dev->req_seq = seq_or_req_seq;
>>                 if ((find_req_seq ? dev->req_seq : dev->seq) ==
>>                                 seq_or_req_seq) {
>>                         *devp = dev;
>> --
>> 2.23.0
>>
>>
>>
-- 
-----
Rudolf J Streif
CEO/CTO ibeeto
+1.855.442.3386 x700


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