linux-kernel - Re: [PATCH 2/3] dmaengine: Add Slave and Cyclic mode support for Actions Semi Owl S900 SoC

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Message-ID: <20180918163512.GE2613@vkoul-mobl>
Date:   Tue, 18 Sep 2018 09:35:12 -0700
From:   Vinod <vkoul@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     dan.j.williams@...el.com, afaerber@...e.de, robh+dt@...nel.org,
        gregkh@...uxfoundation.org, jslaby@...e.com,
        linux-serial@...r.kernel.org, dmaengine@...r.kernel.org,
        liuwei@...ions-semi.com, 96boards@...obotics.com,
        devicetree@...r.kernel.org, daniel.thompson@...aro.org,
        amit.kucheria@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, hzhang@...obotics.com,
        bdong@...obotics.com, manivannanece23@...il.com,
        thomas.liau@...ions-semi.com, jeff.chen@...ions-semi.com,
        pn@...x.de, edgar.righi@...tec.org.br
Subject: Re: [PATCH 2/3] dmaengine: Add Slave and Cyclic mode support for
 Actions Semi Owl S900 SoC

On 01-09-18, 22:12, Manivannan Sadhasivam wrote:

> @@ -364,6 +372,26 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
>  			OWL_DMA_MODE_DT_DCU | OWL_DMA_MODE_SAM_INC |
>  			OWL_DMA_MODE_DAM_INC;
>  
> +		break;
> +	case DMA_MEM_TO_DEV:
> +		mode |= OWL_DMA_MODE_TS(vchan->drq)
> +			| OWL_DMA_MODE_ST_DCU | OWL_DMA_MODE_DT_DEV
> +			| OWL_DMA_MODE_SAM_INC | OWL_DMA_MODE_DAM_CONST;
> +
> +		/* Handle bus width for UART */
> +		if (sconfig->dst_addr_width == DMA_SLAVE_BUSWIDTH_1_BYTE)
> +			mode |= OWL_DMA_MODE_NDDBW_8BIT;

this is fine per se, but not correct way to handle in dmaengine driver.
You should be agnostic to user of dmaengine, so handle all the buswidths
the IP block supports and update the values accordingly. That way new
uses can be added w/o requiring change in dmaengine driver

-- 
~Vinod