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

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Message-ID: <CAH=2Ntw6XcyB2zy-cs35z3eOf8iTa28hGerhLndOgARrG05gJw@mail.gmail.com>
Date:   Fri, 17 Feb 2023 09:30:55 +0530
From:   Bhupesh Sharma <bhupesh.sharma@...aro.org>
To:     Vladimir Zapolskiy <vladimir.zapolskiy@...aro.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, vkoul@...nel.org,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v7 1/1] dma: qcom: bam_dma: Add support to initialize
 interconnect path

On Thu, 16 Feb 2023 at 19:49, Vladimir Zapolskiy
<vladimir.zapolskiy@...aro.org> wrote:
>
> On 9/21/22 06:06, 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
>
> Apparently it's proven that the change description is incorrect, Qualcomm
> crypto engine is working fine on SM8250 and even more recent platforms,
> so far there is no obvious necessity in this change.

Since your v9 patchset produces no entry in $ cat /proc/crypto on
either RB5 (qrb5165) or (with an additional patch) on sm8150-mtp or
sa8115p-adp with the default arm64 defconfig with linux-next, I am not
sure we can conclude QCE is working with these changes.

Please share more details on how you tested this.

Regards,
Bhupesh

> > 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;
> > +     }
> > +
> >       ret = clk_prepare_enable(bdev->bamclk);
> >       if (ret) {
> >               dev_err(bdev->dev, "failed to prepare/enable clock\n");
>
> I'm resurrecting the comments on this change to emphasize the observation
> that the change is not needed at all to run QCE.
>
> --
> Best wishes,
> Vladimir