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

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Message-ID: <a5b6255c-7282-32ed-8031-a4b841a78db7@linaro.org>
Date:   Thu, 16 Feb 2023 16:18:57 +0200
From:   Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
To:     Bhupesh Sharma <bhupesh.sharma@...aro.org>,
        dmaengine@...r.kernel.org
Cc:     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 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.

> 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