linux-kernel - Re: [PATCH RESEND] dmaengine: at_xdmac: get the number of DMA channels from device tree

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Message-ID: <CA+HBbNGv1YzZhBfAO7JvossJeM46CFcPmUtDmYaK4Fm8iB9stg@mail.gmail.com>
Date: Tue, 30 Dec 2025 14:19:05 +0100
From: Robert Marko <robert.marko@...tura.hr>
To: Vinod Koul <vkoul@...nel.org>
Cc: ludovic.desroches@...rochip.com, linux-arm-kernel@...ts.infradead.org, 
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org, 
	daniel.machon@...rochip.com, luka.perkov@...tura.hr, 
	Tony Han <tony.han@...rochip.com>
Subject: Re: [PATCH RESEND] dmaengine: at_xdmac: get the number of DMA
 channels from device tree

On Tue, Dec 16, 2025 at 4:18 PM Vinod Koul <vkoul@...nel.org> wrote:
>
> On 03-12-25, 13:11, Robert Marko wrote:
> > From: Tony Han <tony.han@...rochip.com>
> >
> > In case of kernel runs in non-secure mode, the number of DMA channels can
> > be got from device tree since the value read from GTYPE register is "0" as
> > it's always secured.
> >
> > As the number of channels can never be negative, update them to the type
> > "unsigned".
> >
> > This is required for LAN969x.
>
> You updated the changelog, but tagged it as resend. It should be v2!

Hi,
Sorry for this, I sent the wrong patch and though quickly resending
the right one would be better.

>
> >
> > Signed-off-by: Tony Han <tony.han@...rochip.com>
> > Signed-off-by: Robert Marko <robert.marko@...tura.hr>
> > ---
> >  drivers/dma/at_xdmac.c | 26 +++++++++++++++++++++++---
> >  1 file changed, 23 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
> > index 3fbc74710a13..acabf82e293c 100644
> > --- a/drivers/dma/at_xdmac.c
> > +++ b/drivers/dma/at_xdmac.c
> > @@ -2257,12 +2257,29 @@ static int __maybe_unused atmel_xdmac_runtime_resume(struct device *dev)
> >       return clk_enable(atxdmac->clk);
> >  }
> >
> > +static inline int at_xdmac_get_channel_number(struct platform_device *pdev,
> > +                                           u32 reg, u32 *pchannels)
> > +{
> > +     int     ret;
> > +
> > +     if (reg) {
> > +             *pchannels = AT_XDMAC_NB_CH(reg);
> > +             return 0;
> > +     }
> > +
> > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels", pchannels);
> > +     if (ret)
> > +             dev_err(&pdev->dev, "can't get number of channels\n");
>
> Do we need to log error, I thought the API did that...

I dont think API helps here, we would just be left with the error
code, which can be hard
to trace back but I am flexible.

Regards,
Robert
>
> > +
> > +     return ret;
> > +}
> > +
> >  static int at_xdmac_probe(struct platform_device *pdev)
> >  {
> >       struct at_xdmac *atxdmac;
> > -     int             irq, nr_channels, i, ret;
> > +     int             irq, ret;
> >       void __iomem    *base;
> > -     u32             reg;
> > +     u32             nr_channels, i, reg;
> >
> >       irq = platform_get_irq(pdev, 0);
> >       if (irq < 0)
> > @@ -2278,7 +2295,10 @@ static int at_xdmac_probe(struct platform_device *pdev)
> >        * of channels to do the allocation.
> >        */
> >       reg = readl_relaxed(base + AT_XDMAC_GTYPE);
> > -     nr_channels = AT_XDMAC_NB_CH(reg);
> > +     ret = at_xdmac_get_channel_number(pdev, reg, &nr_channels);
> > +     if (ret)
> > +             return ret;
> > +
> >       if (nr_channels > AT_XDMAC_MAX_CHAN) {
> >               dev_err(&pdev->dev, "invalid number of channels (%u)\n",
> >                       nr_channels);
> > --
> > 2.52.0
>
> --
> ~Vinod



-- 
Robert Marko
Staff Embedded Linux Engineer
Sartura d.d.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko@...tura.hr
Web: www.sartura.hr