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

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Date:   Thu, 22 Sep 2022 08:08:13 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Bhupesh Sharma <bhupesh.sharma@...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, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v7 1/1] dma: qcom: bam_dma: Add support to initialize
 interconnect path

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?

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

-- 
~Vinod