linux-kernel - Re: [PATCH v2] media: omap3isp: Use dma_request_chan_by

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Message-ID: <4166499.xzsPgrmGQ7@avalon>
Date:   Fri, 04 Nov 2016 17:46:03 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     mchehab@....samsung.com, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] media: omap3isp: Use dma_request_chan_by_mask() to request the DMA channel

Hi Peter,

Thank you for the patch.

On Friday 04 Nov 2016 09:58:02 Peter Ujfalusi wrote:
> When requesting the DMA channel it was mandatory that we do not have DMA
> resource nor valid DMA channel via DT. In this case the
> dma_request_slave_channel_compat() would fall back and request any channel
> with SW trigger.
> 
> The same can be achieved with the dma_request_chan_by_mask() without the
> misleading use of the DMAengine API - implying that the omap3isp does
> need to have DMA resource or valid dma binding in DT.
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> CC: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> CC: Mauro Carvalho Chehab <mchehab@....samsung.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

and added to my tree.

> ---
> Hi,
> 
> Changes sicne v1:
> - use dma_request_chan_by_mask() to request the channel as for the histogram
> data reading we do not have hw syncronisation. Add comment about this also
> to clarify the reason.
> 
> Regards,
> Peter
> 
>  drivers/media/platform/omap3isp/isphist.c | 28 +++++++++++++++-------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/platform/omap3isp/isphist.c
> b/drivers/media/platform/omap3isp/isphist.c index
> 7138b043a4aa..a4ed5d140d48 100644
> --- a/drivers/media/platform/omap3isp/isphist.c
> +++ b/drivers/media/platform/omap3isp/isphist.c
> @@ -18,7 +18,6 @@
>  #include <linux/delay.h>
>  #include <linux/device.h>
>  #include <linux/dmaengine.h>
> -#include <linux/omap-dmaengine.h>
>  #include <linux/slab.h>
>  #include <linux/uaccess.h>
> 
> @@ -486,27 +485,30 @@ int omap3isp_hist_init(struct isp_device *isp)
>  	hist->isp = isp;
> 
>  	if (HIST_CONFIG_DMA) {
> -		struct platform_device *pdev = to_platform_device(isp->dev);
> -		struct resource *res;
> -		unsigned int sig = 0;
>  		dma_cap_mask_t mask;
> 
> +		/*
> +		 * We need slave capable channel without DMA request line for
> +		 * reading out the data.
> +		 * For this we can use dma_request_chan_by_mask() as we are
> +		 * happy with any channel as long as it is capable of slave
> +		 * configuration.
> +		 */
>  		dma_cap_zero(mask);
>  		dma_cap_set(DMA_SLAVE, mask);
> +		hist->dma_ch = dma_request_chan_by_mask(&mask);
> +		if (IS_ERR(hist->dma_ch)) {
> +			ret = PTR_ERR(hist->dma_ch);
> +			if (ret == -EPROBE_DEFER)
> +				return ret;
> 
> -		res = platform_get_resource_byname(pdev, IORESOURCE_DMA,
> -						   "hist");
> -		if (res)
> -			sig = res->start;
> -
> -		hist->dma_ch = dma_request_slave_channel_compat(mask,
> -				omap_dma_filter_fn, &sig, isp->dev, "hist");
> -		if (!hist->dma_ch)
> +			hist->dma_ch = NULL;
>  			dev_warn(isp->dev,
>  				 "hist: DMA channel request failed, using 
PIO\n");
> -		else
> +		} else {
>  			dev_dbg(isp->dev, "hist: using DMA channel %s\n",
>  				dma_chan_name(hist->dma_ch));
> +		}
>  	}
> 
>  	hist->ops = &hist_ops;

-- 
Regards,

Laurent Pinchart