On Fri, 19 May 2023 at 16:30, Stephan Gerhold <stephan@xxxxxxxxxxx> wrote: > > The bam_dma driver needs to know the number of channels and execution > environments (EEs) at probe time. If we are in full control of the BAM > controller this information can be obtained from the BAM identification > registers (BAM_REVISION/BAM_NUM_PIPES). > > When the BAM is "controlled remotely" it is more complicated. The BAM > might not be on at probe time, so reading the registers could fail. > This is why the information must be added to the device tree in this > case, using "num-channels" and "qcom,num-ees". > > However, there are also some BAM instances that are initialized by > something else but we still have a clock that allows to turn it on when > needed. This can be set up in the DT with "qcom,controlled-remotely" > and "clocks" and is already supported by the bam_dma driver. Examples > for this are the typical BLSP BAM instances on older SoCs, QPIC BAM > (for NAND) and the crypto BAM on some SoCs. > > In this case, there is no need to read "num-channels" and > "qcom,num-ees" from the DT. The BAN can be turned on using the clock > so we can just read it from the BAM registers like in the normal case. > > Check for the BAM clock earlier and skip reading "num-channels" and > "qcom,num-ees" if it is present to allow simplifying the DT description > a bit. > > Signed-off-by: Stephan Gerhold <stephan@xxxxxxxxxxx> > --- > Changes in v2: > - Rewrite commit message for more clarity (discussion with Bhupesh) > - Link to v1: https://lore.kernel.org/r/20230518-bamclk-dt-v1-1-82f738c897d9@xxxxxxxxxxx > --- > drivers/dma/qcom/bam_dma.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c > index 1e47d27e1f81..4c3eb972039d 100644 > --- a/drivers/dma/qcom/bam_dma.c > +++ b/drivers/dma/qcom/bam_dma.c > @@ -1272,7 +1272,15 @@ static int bam_dma_probe(struct platform_device *pdev) > bdev->powered_remotely = of_property_read_bool(pdev->dev.of_node, > "qcom,powered-remotely"); > > - if (bdev->controlled_remotely || bdev->powered_remotely) { > + if (bdev->controlled_remotely || bdev->powered_remotely) > + bdev->bamclk = devm_clk_get_optional(bdev->dev, "bam_clk"); > + else > + bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk"); > + > + if (IS_ERR(bdev->bamclk)) > + return PTR_ERR(bdev->bamclk); > + > + if (!bdev->bamclk) { > ret = of_property_read_u32(pdev->dev.of_node, "num-channels", > &bdev->num_channels); > if (ret) > @@ -1284,14 +1292,6 @@ static int bam_dma_probe(struct platform_device *pdev) > dev_err(bdev->dev, "num-ees unspecified in dt\n"); > } > > - if (bdev->controlled_remotely || bdev->powered_remotely) > - bdev->bamclk = devm_clk_get_optional(bdev->dev, "bam_clk"); > - else > - bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk"); > - > - if (IS_ERR(bdev->bamclk)) > - return PTR_ERR(bdev->bamclk); > - > ret = clk_prepare_enable(bdev->bamclk); > if (ret) { > dev_err(bdev->dev, "failed to prepare/enable clock\n"); Reviewed-by: Bhupesh Sharma <bhupesh.sharma@xxxxxxxxxx> Thanks.
