linux-kernel - Re: [PATCH v7 1/1] dma: qcom: bam_dma: Add support to initialize interconnect path

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Date:   Fri, 23 Sep 2022 10:40:31 +0530
From:   Bhupesh Sharma <bhupesh.sharma@...aro.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     dmaengine@...r.kernel.org, agross@...nel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, thara.gopinath@...il.com,
        devicetree@...r.kernel.org, andersson@...nel.org,
        bhupesh.linux@...il.com, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v7 1/1] dma: qcom: bam_dma: Add support to initialize
 interconnect path

On Thu, 22 Sept 2022 at 08:08, Vinod Koul <vkoul@...nel.org> wrote:
>
> On 21-09-22, 08:36, Bhupesh Sharma wrote:
> > From: Thara Gopinath <thara.gopinath@...il.com>
> >
> > BAM dma engine associated with certain hardware blocks could require
> > relevant interconnect pieces be initialized prior to the dma engine
> > initialization. For e.g. crypto bam dma engine on sm8250. Such requirement
> > is passed on to the bam dma driver from dt via the "interconnects"
> > property. Add support in bam_dma driver to check whether the interconnect
> > path is accessible/enabled prior to attempting driver intializations.
> >
> > If interconnects are not yet setup, defer the BAM DMA driver probe().
> >
> > Cc: Bjorn Andersson <andersson@...nel.org>
> > Cc: Rob Herring <robh@...nel.org>
> > Signed-off-by: Thara Gopinath <thara.gopinath@...il.com>
> > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@...aro.org>
> > [Bhupesh: Make header file inclusion alphabetical and use 'devm_of_icc_get()']
> > ---
> >  drivers/dma/qcom/bam_dma.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> > index 2ff787df513e..a5b0cf28ffb7 100644
> > --- a/drivers/dma/qcom/bam_dma.c
> > +++ b/drivers/dma/qcom/bam_dma.c
> > @@ -26,6 +26,7 @@
> >  #include <linux/kernel.h>
> >  #include <linux/io.h>
> >  #include <linux/init.h>
> > +#include <linux/interconnect.h>
> >  #include <linux/slab.h>
> >  #include <linux/module.h>
> >  #include <linux/interrupt.h>
> > @@ -394,6 +395,7 @@ struct bam_device {
> >       const struct reg_offset_data *layout;
> >
> >       struct clk *bamclk;
> > +     struct icc_path *mem_path;
> >       int irq;
> >
> >       /* dma start transaction tasklet */
> > @@ -1294,6 +1296,14 @@ static int bam_dma_probe(struct platform_device *pdev)
> >       if (IS_ERR(bdev->bamclk))
> >               return PTR_ERR(bdev->bamclk);
> >
> > +     /* Ensure that interconnects are initialized */
> > +     bdev->mem_path = devm_of_icc_get(bdev->dev, "memory");
> > +     if (IS_ERR(bdev->mem_path)) {
> > +             ret = dev_err_probe(bdev->dev, PTR_ERR(bdev->mem_path),
> > +                                 "failed to acquire icc path\n");
> > +             return ret;
> > +     }
>
> So this makes us fail on older DT where icc path may not be present.
> Should this not be an optional thing?

That's a good point. I am not sure if Thara tried this on platforms
which don't have the icc path available.

I will fix this in v8.

Thanks,
Bhupesh

> > +
> >       ret = clk_prepare_enable(bdev->bamclk);
> >       if (ret) {
> >               dev_err(bdev->dev, "failed to prepare/enable clock\n");
> > --
> > 2.37.1
>
> --
> ~Vinod