Re: [PATCH] dmaengine: pl08x: mark slave channels as DMA_PRIVATE

[Frank Li]

On Tue, Oct 27, 2026 at 08:00:37AM +0100, Andreas Gabriel-Platschek wrote:
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>
> The pl08x slave engine channels are only ever handed out through
> explicit requests: DT clients go via pl08x_of_xlate() and the
> platform-data path uses dma_request_channel() with a filter, both of
> which end up in dma_get_slave_channel(). They are not meant to be
> published in the general-purpose channel table.
>
> Mark the slave device with DMA_PRIVATE at probe time so the dmaengine
> core treats it as always-private. Without this, if a dmaengine client
> is already active when the device is registered,
> dma_async_device_register() takes a reference on every channel,

Code change is okay. Are you sure the above description correct? where
code set it active when dma_async_device_register().

Frank

> and
> the subsequent dma_get_slave_channel() from pl08x_of_xlate() fails
> because the channel is no longer free (client_count != 0), leaving DT
> slave clients unable to acquire channels.
>
> The memcpy engine stays public as it is intended to be shared through
> the per-CPU channel table.
>
> Signed-off-by: Andreas Gabriel-Platschek <andi.platschek@xxxxxxxxx>
> ---
>  drivers/dma/amba-pl08x.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
> index 543c2eb8cfa8..06881d3f29a9 100644
> --- a/drivers/dma/amba-pl08x.c
> +++ b/drivers/dma/amba-pl08x.c
> @@ -2775,6 +2775,7 @@ static int pl08x_probe(struct amba_device *adev, const struct amba_id *id)
>                 pl08x->has_slave = true;
>                 dma_cap_set(DMA_SLAVE, pl08x->slave.cap_mask);
>                 dma_cap_set(DMA_CYCLIC, pl08x->slave.cap_mask);
> +               dma_cap_set(DMA_PRIVATE, pl08x->slave.cap_mask);
>                 pl08x->slave.dev = &adev->dev;
>                 pl08x->slave.device_free_chan_resources =
>                         pl08x_free_chan_resources;
> --
> 2.47.3
>