linux-kernel - Re: [PATCH 1/1] spi: pxa2xx: add driver enabling message

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Date:   Wed, 10 Apr 2019 12:54:31 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Flavio Suligoi <f.suligoi@...m.it>
Cc:     Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] spi: pxa2xx: add driver enabling message

On Wed, Apr 10, 2019 at 11:47:43AM +0000, Flavio Suligoi wrote:

> You have right about to avoid too many boot messages,
> but in this case, using an x86 machine and with
> the spi-pxa2xx in DMA mode, so without the message: 

> "no DMA channels available, using PIO",

> there is absolutely no indication about the existence
> of the SPI master controller.

It's totally fine to not have a boot print for the device, the best way
to find devices if you need them is to look in sysfs anyway.

> The second reason is about the DMA/PIO mode indication. 
> With the board I'm using, sometimes the spi-pxa2xx driver can't allocate
> a DMA channel and works in PIO mode.

> So, with the advice of Jarkko, I think that a valid solution could be:

> 1) remove the "no DMA channels available, using PIO" message
> 2) add a new message with the indications of:
> 	- controller mode (slave or master)
> 	- transfer mode (DMA or PIO)

> What do you think about this?

If the system is randomly failing to assign a DMA channel when it should
then shouldn't we just fix that?  A print which is presumably intended
to prompt the user to reboot to try to get things working doesn't seem
like a good solution.

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