Re: [PATCH 1/1] spi: spi-imx: Use dev_err_probe for failed DMA channel requests

[Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>]

Hi Fabio,

Am Mittwoch, 31. Mai 2023, 15:14:37 CEST schrieb Fabio Estevam:
> Hi Alexander,
> 
> On Tue, Apr 18, 2023 at 5:35 AM Alexander Stein
> 
> <alexander.stein@xxxxxxxxxxxxxxx> wrote:
> > If dma_request_chan() fails, no error is shown nor any information is
> > shown in /sys/kernel/debug/devices_deferred if -EPROBE_DEFER is returned.
> > Use dev_err_probe to fix both problems.
> 
> Running spi-imx without SDMA is valid and not an error, right?

That might be true, but this is not what this patch is about.

> I am not sure I understood the real motivation for this patch.

If the call to dma_request_chan() for either DMA channel 'rx' and 'tx' returns 
-EPROBE_DEFER, spi-imx will return that error code as well. So far so good.
You can check /sys/kernel/debug/devices_deferred to see which devices got 
deferred and not probed yet.
Without this patch spi-imx will be listed without any additional information 
about cause of the deferral. Finding the cause with no additional information 
is cumbersome, it's hidden in dev_dbg().

Using this patch additional information is provided, e.g. "can't get the TX 
DMA channel!". So you know right away spi-imx is not probing because the DMA 
channel is not available.

I hope this shows the motivation for this change.
Best regards,
Alexander

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