Hi Vinod,
On Thu, Jun 16, 2022 at 06:58:43AM -0700, Vinod Koul wrote:
> On 14-06-22, 12:17, Dario Binacchi wrote:
> > Driver registration fails on SOC imx8mn as its supplier, the clock
> > control module, is not ready. Since platform_driver_probe(), as
> > reported by its description, is incompatible with deferred probing,
> > we have to use platform_driver_register().
> >
> > Fixes: a580b8c5429a ("dmaengine: mxs-dma: add dma support for i.MX23/28")
> > Co-developed-by: Michael Trimarchi <michael@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Michael Trimarchi <michael@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Dario Binacchi <dario.binacchi@xxxxxxxxxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> >
> > ---
> >
> > Changes in v3:
> > - Restore __init in front of mxs_dma_init() definition.
> >
> > Changes in v2:
> > - Add the tag "Cc: stable@xxxxxxxxxxxxxxx" in the sign-off area.
> >
> > drivers/dma/mxs-dma.c | 9 +++------
> > 1 file changed, 3 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
> > index 994fc4d2aca4..6e90540fedc4 100644
> > --- a/drivers/dma/mxs-dma.c
> > +++ b/drivers/dma/mxs-dma.c
> > @@ -741,7 +741,7 @@ static struct dma_chan *mxs_dma_xlate(struct of_phandle_args *dma_spec,
> > ofdma->of_node);
> > }
> >
> > -static int __init mxs_dma_probe(struct platform_device *pdev)
> > +static int mxs_dma_probe(struct platform_device *pdev)
>
> why drop __init here, if there is a reason for that please split this
> change and document such reason...
The reason for dropping __init comes with this patch. With
platform_driver_probe() the probe function is called only once, during
init time. The problem with platform_driver_probe() is that the probe
function will never be called again when it initially returns
-EPROBE_DEFER. That's a problem for Dario: The clock is not yet
available, the driver defers probe and will never be probed again
when the clock is finally available.
With platform_driver_register() to which this patch switches to the
probe function can be called at any time, thus __init has to be removed.
For what it's worth:
Acked-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
for this patch.
Sascha
>
> > {
> > struct device_node *np = pdev->dev.of_node;
> > const struct mxs_dma_type *dma_type;
> > @@ -839,10 +839,7 @@ static struct platform_driver mxs_dma_driver = {
> > .name = "mxs-dma",
> > .of_match_table = mxs_dma_dt_ids,
> > },
> > + .probe = mxs_dma_probe,
> > };
> >
> > -static int __init mxs_dma_module_init(void)
> > -{
> > - return platform_driver_probe(&mxs_dma_driver, mxs_dma_probe);
> > -}
> > -subsys_initcall(mxs_dma_module_init);
> > +module_platform_driver(mxs_dma_driver);
> > --
> > 2.32.0
>
> --
> ~Vinod
>
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