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    SubjectRe: [PATCH v5 18/22] crypto: qce: Defer probing if BAM dma channel is not yet initialized
    On Wed 10 Nov 04:59 CST 2021, 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.
    >

    To me this sentence implies that qce_crypto_probe() doesn't return
    -EPROBE_DEFER from qce_dma_request(), but looking at the code I don't
    see why this would be...

    > 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.
    >

    As far as I can tell the only actual difference is that you're moving
    the qce_dma_request() above the icc_set_bw() call and the three
    clk_prepare_enable() calls.

    This is a very valid optimization, but where does qce_crypto_probe()
    fail and why does it need the BAM driver to have probed before we try to
    turn on the clocks and (our) interconnect vote?

    > Cc: Thara Gopinath <thara.gopinath@linaro.org>
    > Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
    > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>
    > ---
    > drivers/crypto/qce/core.c | 23 ++++++++++++++---------
    > 1 file changed, 14 insertions(+), 9 deletions(-)
    >
    > diff --git a/drivers/crypto/qce/core.c b/drivers/crypto/qce/core.c
    > index 7c90401a2ef1..84ed9e253d5d 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.
    > + * In case the dma channel are not set yet, this check
    > + * helps use to return -EPROBE_DEFER earlier.
    > + */

    This comment warrants the change, but I don't see that it will add value
    in the code once the patch is merged. Please drop it.

    > + ret = qce_dma_request(qce->dev, &qce->dma);
    > + if (ret)

    I presume this is where your added dev_err() in err: comes in handy. I
    definitely think this warrants an error print; so return dev_err_probe()
    here would be the right thing to do (in the previous patch).

    > + return ret;
    > +
    > qce->mem_path = devm_of_icc_get(qce->dev, "memory");
    > - if (IS_ERR(qce->mem_path))
    > - return PTR_ERR(qce->mem_path);

    But I see no reason for moving it above devm_of_icc_get() and the
    devm_clk_get*() calls - as they don't actually do anything, but moving
    qce_dma_request() above them forces the introduction of goto here.

    Regards,
    Bjorn

    > + if (IS_ERR(qce->mem_path)) {
    > + ret = PTR_ERR(qce->mem_path);
    > + goto err;
    > + }
    >
    > 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:
    > @@ -280,6 +284,7 @@ static int qce_crypto_probe(struct platform_device *pdev)
    > err_mem_path_disable:
    > icc_set_bw(qce->mem_path, 0, 0);
    > err:
    > + qce_dma_release(&qce->dma);
    > dev_err(dev, "%s failed : %d\n", __func__, ret);
    > return ret;
    > }
    > --
    > 2.31.1
    >

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