linux-kernel - Re: [PATCH 2/2] spi: pxa2xx: use a module softdep for dw

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Date:   Wed, 10 Apr 2019 16:28:20 +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 2/2] spi: pxa2xx: use a module softdep for dw_dmac

On Wed, Apr 10, 2019 at 02:05:38PM +0000, Flavio Suligoi wrote:
> Hi Mark,

> > While this isn't going to hurt anything and might actually help so it's
> > fine doesn't this also suggest that there's an issue with deferred probe
> > going on as well?

> I think that the problem could be related to how the DMA channel is requested.
> At the moment the function used are:

> pxa2xx_spi_dma_setup --> dma_request_slave_channel_compat -->
> --> __dma_request_slave_channel_compat --> dma_request_slave_channel -->
> --> dma_request_chan

> Actually the final function "dma_request_chan" return
> the channel number or "-EPROBE_DEFER" if it's not ready.
> But this information ("-EPROBE_DEFER") is lost in the penultimate function 
> "dma_request_slave_channel", which return only the chann, if all is ok, or
> NULL, in case of errors.
> So the deferral mechanism is not used.

Right, yes - that analysis seems correct.  The interfaces seem a bit
weird here but fixing them looks like the most complete and robust fix.

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