linux-kernel - Re: [PATCH v4 02/10] dmaengine: Actions: Add support for S700 DMA engine

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Message-ID: <20200624061529.GF2324254@vkoul-mobl>
Date:   Wed, 24 Jun 2020 11:45:29 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Amit Singh Tomar <amittomer25@...il.com>
Cc:     andre.przywara@....com, afaerber@...e.de,
        manivannan.sadhasivam@...aro.org, dan.j.williams@...el.com,
        cristian.ciocaltea@...il.com, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-actions@...ts.infradead.org
Subject: Re: [PATCH v4 02/10] dmaengine: Actions: Add support for S700 DMA
 engine

Hi Amit,

On 09-06-20, 15:47, Amit Singh Tomar wrote:

> @@ -372,6 +383,7 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
>  				  struct dma_slave_config *sconfig,
>  				  bool is_cyclic)
>  {
> +	struct owl_dma *od = to_owl_dma(vchan->vc.chan.device);
>  	u32 mode, ctrlb;
>  
>  	mode = OWL_DMA_MODE_PW(0);
> @@ -427,14 +439,26 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
>  	lli->hw[OWL_DMADESC_DADDR] = dst;
>  	lli->hw[OWL_DMADESC_SRC_STRIDE] = 0;
>  	lli->hw[OWL_DMADESC_DST_STRIDE] = 0;
> -	/*
> -	 * Word starts from offset 0xC is shared between frame length
> -	 * (max frame length is 1MB) and frame count, where first 20
> -	 * bits are for frame length and rest of 12 bits are for frame
> -	 * count.
> -	 */
> -	lli->hw[OWL_DMADESC_FLEN] = len | FCNT_VAL << 20;
> -	lli->hw[OWL_DMADESC_CTRLB] = ctrlb;
> +
> +	if (od->devid == S700_DMA) {
> +		/* Max frame length is 1MB */
> +		lli->hw[OWL_DMADESC_FLEN] = len;
> +		/*
> +		 * On S700, word starts from offset 0x1C is shared between
> +		 * frame count and ctrlb, where first 12 bits are for frame
> +		 * count and rest of 20 bits are for ctrlb.
> +		 */
> +		lli->hw[OWL_DMADESC_CTRLB] = FCNT_VAL | ctrlb;
> +	} else {
> +		/*
> +		 * On S900, word starts from offset 0xC is shared between
> +		 * frame length (max frame length is 1MB) and frame count,
> +		 * where first 20 bits are for frame length and rest of
> +		 * 12 bits are for frame count.
> +		 */
> +		lli->hw[OWL_DMADESC_FLEN] = len | FCNT_VAL << 20;
> +		lli->hw[OWL_DMADESC_CTRLB] = ctrlb;

Unfortunately this wont scale, we will keep adding new conditions for
newer SoC's! So rather than this why not encode max frame length in
driver_data rather than S900_DMA/S700_DMA.. In future one can add values
for newer SoC and not code above logic again.

> +static const struct of_device_id owl_dma_match[] = {
> +	{ .compatible = "actions,s900-dma", .data = (void *)S900_DMA,},
> +	{ .compatible = "actions,s700-dma", .data = (void *)S700_DMA,},

Is the .compatible documented, Documentation patch should come before
the driver use patch in a series

>  static int owl_dma_probe(struct platform_device *pdev)
>  {
>  	struct device_node *np = pdev->dev.of_node;
>  	struct owl_dma *od;
>  	int ret, i, nr_channels, nr_requests;
> +	const struct of_device_id *of_id =
> +				of_match_device(owl_dma_match, &pdev->dev);

You care about driver_data rather than of_id, so using
of_device_get_match_data() would be better..

>  	od = devm_kzalloc(&pdev->dev, sizeof(*od), GFP_KERNEL);
>  	if (!od)
> @@ -1083,6 +1116,8 @@ static int owl_dma_probe(struct platform_device *pdev)
>  	dev_info(&pdev->dev, "dma-channels %d, dma-requests %d\n",
>  		 nr_channels, nr_requests);
>  
> +	od->devid = (enum owl_dma_id)(uintptr_t)of_id->data;

Funny casts, I dont think you need uintptr_t!
-- 
~Vinod