U-CLASS SPI Bus and Devices

[Simon Glass]

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.

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
>
>
>