linux-kernel - Re: [PATCH RESEND] media: omap3isp: Use dma_request

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Date:   Wed, 02 Nov 2016 23:19:36 +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 RESEND] media: omap3isp: Use dma_request_chan() to requesting DMA channel

Hi Peter,

Thank you for the patch.

On Wednesday 02 Nov 2016 14:39:59 Peter Ujfalusi wrote:
> With the new dma_request_chan() the client driver does not need to look for
> the DMA resource and it does not need to pass filter_fn anymore.
> By switching to the new API the driver can now support deferred probing
> against DMA.

I believe this breaks the OMAP3 ISP driver. dma_request_slave_channel_compat() 
is a superset of dma_request_chan() that will, when called with 
omap_dma_filter_fn, return as a fallback any free channel handled by the OMAP 
DMA engine driver. This feature is actively used by this driver and must be 
preserved.

> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> CC: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> CC: Mauro Carvalho Chehab <mchehab@....samsung.com>
> ---
> Hi,
> 
> the original patch was sent 29.04.2016:
> https://patchwork.kernel.org/patch/8981811/
> 
> I have rebased it on top of linux-next.
> 
> Regards,
> Peter
> 
>  drivers/media/platform/omap3isp/isphist.c | 27 +++++++++------------------
>  1 file changed, 9 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/media/platform/omap3isp/isphist.c
> b/drivers/media/platform/omap3isp/isphist.c index
> 7138b043a4aa..e163e3d92517 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 +485,19 @@ 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;
> -
> -		dma_cap_zero(mask);
> -		dma_cap_set(DMA_SLAVE, mask);
> -
> -		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 = dma_request_chan(isp->dev, "hist");
> +		if (IS_ERR(hist->dma_ch)) {
> +			ret = PTR_ERR(hist->dma_ch);
> +			if (ret == -EPROBE_DEFER)
> +				return ret;
> +
> +			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