[PATCH V3] dmaengine: imx-sdma: Fix SPBA bus detection on multi-SPBA platforms

[Marco Felsch]

On 26-04-21, Shengjiu Wang wrote:
> On Tue, Apr 21, 2026 at 4:57 PM Marco Felsch <m.felsch at pengutronix.de> wrote:
> >
> > On 26-04-20, Shengjiu Wang wrote:
> > > i.MX8M platforms have multiple SPBA buses under different AIPS buses.
> > > The current code searches the entire device tree and returns the first
> > > SPBA bus found, which may not be under the same AIPS bus as the SDMA
> > > controller.
> > >
> > > This breaks SDMA P2P transfers because the SDMA script needs to know
> > > if peripherals are on SPBA or AIPS to configure watermark levels
> > > correctly. Using the wrong SPBA bus causes DMA timeouts and transfer
> > > failures.
> > >
> > > Fix by searching for the SPBA bus under the SDMA's parent node (AIPS)
> > > first, then falling back to a global search for backward compatibility.
> > >
> > > Example device tree showing the issue:
> > >   aips1 {
> > >     spba1 { sai at ...; };      /* Correct SPBA for sdma1 */
> > >     sdma1 at ...;
> > >   };
> > >   aips2 {
> > >     spba2 { uart at ...; };     /* Wrong SPBA - found first by old code */
> > >   };
> > >
> > > Fixes: 8391ecf465ec ("dmaengine: imx-sdma: Add device to device support")
> > > Cc: stable at vger.kernel.org
> > > Signed-off-by: Shengjiu Wang <shengjiu.wang at nxp.com>
> > > ---
> > > changs in v3:
> > > - add fallback to a global search for backward compatibility, which is
> > >   to address comments from sashiko.dev
> > > - update commit subject and commit message
> > > - add comments in code.
> > > - add Cc stable tag
> > > - Don't add Frank's RB on v2 as there are several other changes.
> > >
> > > changes in v2:
> > > - add fixes tag
> > > - use __free(device_node) for auto release.
> > >
> > >  drivers/dma/imx-sdma.c | 13 ++++++++++++-
> > >  1 file changed, 12 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> > > index 3d527883776b..592705af2319 100644
> > > --- a/drivers/dma/imx-sdma.c
> > > +++ b/drivers/dma/imx-sdma.c
> > > @@ -2364,7 +2364,18 @@ static int sdma_probe(struct platform_device *pdev)
> > >                       return dev_err_probe(&pdev->dev, ret,
> > >                                            "failed to register controller\n");
> > >
> > > -             spba_bus = of_find_compatible_node(NULL, NULL, "fsl,spba-bus");
> > > +             /*
> > > +              * On i.MX8M platforms with multiple SPBA buses, we need to find
> > > +              * the SPBA bus that's under the same AIPS bus as this SDMA controller.
> > > +              * First check the SDMA's parent (AIPS bus) for a child SPBA bus.
> > > +              * If not found, fall back to searching the entire device tree for
> > > +              * backward compatibility with older platforms.
> > > +              */
> > > +             struct device_node *sdma_parent_np __free(device_node) = of_get_parent(np);
> > > +
> > > +             spba_bus = of_get_compatible_child(sdma_parent_np, "fsl,spba-bus");
> > > +             if (!spba_bus)
> > > +                     spba_bus = of_find_compatible_node(NULL, NULL, "fsl,spba-bus");
> >
> > And yet the search is still broken for i.MX8MP case since this platform
> > has two sdma engines below the bus at 30df0000.
> 
> I tested on i.MX8MP. It works.  Above line is for backward compatibility
> 
> The search has no dependence on the number of sdma engines. It searches the
> spba-bus, not the sdma node. it will find the aips5 first, then find
> the spba-bus for
> sdma2 and sdma3.

And you're abosulte certain that NXP doesn't introduce a 2nd SPBA bus
below the same AIPS in which case the driver is broken again?

Sorry for beeing a bit picky. I do see that NXP decided to drop the SDMA
for i.MX9, at least I don't find any reference in which case I'm fine
with the patch.

Regards,
  Marco




> 
> aips5: bus at 30df0000 {
>       spba-bus at 30c00000 {
>        }
>        sdma2: dma-controller at 30e10000 {
>        }
>        sdma3: dma-controller at 30e00000 {
>       }
> }
> 
> Best regards
> Shengjiu Wang
> 
> >
> > Regards,
> >   Marco
> >
> > >               ret = of_address_to_resource(spba_bus, 0, &spba_res);
> > >               if (!ret) {
> > >                       sdma->spba_start_addr = spba_res.start;
> > > --
> > > 2.34.1
> > >
> > >
> > >
> >
> > --
> > #gernperDu
> > #CallMeByMyFirstName
> >
> > Pengutronix e.K.                           |                             |
> > Steuerwalder Str. 21                       | https://www.pengutronix.de/ |
> > 31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
> > Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-9    |
> >
> 

-- 
#gernperDu 
#CallMeByMyFirstName

Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | https://www.pengutronix.de/ |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-9    |