linux-kernel - Re: [PATCH v4 18/20] crypto: qce: Defer probing if BAM dma channel is not yet initialized

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Date:   Thu, 14 Oct 2021 13:10:01 +0530
From:   Bhupesh Sharma <bhupesh.sharma@...aro.org>
To:     Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
Cc:     MSM <linux-arm-msm@...r.kernel.org>, linux-crypto@...r.kernel.org,
        bhupesh.linux@...il.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v4 18/20] crypto: qce: Defer probing if BAM dma channel is
 not yet initialized

Hi Vladimir,

On Thu, 14 Oct 2021 at 02:19, Vladimir Zapolskiy
<vladimir.zapolskiy@...aro.org> wrote:
>
> Hi Bhupesh,
>
> On 10/13/21 1:55 PM, Bhupesh Sharma wrote:
> > Since the Qualcomm qce crypto driver needs the BAM dma driver to be
> > setup first (to allow crypto operations), it makes sense to defer
> > the qce crypto driver probing in case the BAM dma driver is not yet
> > probed.
> >
> > Move the code leg requesting dma channels earlier in the
> > probe() flow. This fixes the qce probe failure issues when both qce
> > and BMA dma are compiled as static part of the kernel.
> >
> > Cc: Thara Gopinath <thara.gopinath@...aro.org>
> > Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@...aro.org>
> > ---
> >   drivers/crypto/qce/core.c | 20 ++++++++++++--------
> >   1 file changed, 12 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/crypto/qce/core.c b/drivers/crypto/qce/core.c
> > index cb8c77709e1e..c6f686126fc9 100644
> > --- a/drivers/crypto/qce/core.c
> > +++ b/drivers/crypto/qce/core.c
> > @@ -209,9 +209,19 @@ static int qce_crypto_probe(struct platform_device *pdev)
> >       if (ret < 0)
> >               return ret;
> >
> > +     /* qce driver requires BAM dma driver to be setup first.
>
> I believe a multi-line block of comments should be started with '/*' line,
> for reference please take a look at Documentation/process/coding-style.rst

There are exceptions to this rule as well. For e.g. see most of the
networking drivers and the multi-line comment styles there :) .

There is a very interesting LWN article on the same :
https://lwn.net/Articles/694755/
Note that 'crypto/' and 'drivers/crypto' use these non-standard
multi-line comments quite often as well.

That said, I have no strong opinion on using either style. Although, I
found one of the points raised by the networking maintainer during one
of my patch reviews earlier quite useful - 'keeping the top line in a
multi-line comment blank, wastes precious screen space while reading
and reviewing the patch'.

Regards,
Bhupesh

> > +      * In case the dma channel are not set yet, this check
> > +      * helps use to return -EPROBE_DEFER earlier.
> > +      */
> > +     ret = qce_dma_request(qce->dev, &qce->dma);
> > +     if (ret)
> > +             return ret;
> > +
> >       qce->mem_path = of_icc_get(qce->dev, "memory");
> > -     if (IS_ERR(qce->mem_path))
> > +     if (IS_ERR(qce->mem_path)) {
> > +             qce_dma_release(&qce->dma);
> >               return PTR_ERR(qce->mem_path);
> > +     }
> >
> >       qce->core = devm_clk_get_optional(qce->dev, "core");
> >       if (IS_ERR(qce->core)) {
> > @@ -247,10 +257,6 @@ static int qce_crypto_probe(struct platform_device *pdev)
> >       if (ret)
> >               goto err_clks_iface;
> >
> > -     ret = qce_dma_request(qce->dev, &qce->dma);
> > -     if (ret)
> > -             goto err_clks;
> > -
> >       ret = qce_check_version(qce);
> >       if (ret)
> >               goto err_clks;
> > @@ -265,12 +271,10 @@ static int qce_crypto_probe(struct platform_device *pdev)
> >
> >       ret = qce_register_algs(qce);
> >       if (ret)
> > -             goto err_dma;
> > +             goto err_clks;
> >
> >       return 0;
> >
> > -err_dma:
> > -     qce_dma_release(&qce->dma);
> >   err_clks:
> >       clk_disable_unprepare(qce->bus);
> >   err_clks_iface:
> >
>
> --
> Best wishes,
> Vladimir