linux-kernel - Re: [PATCH v2] media: rcar_drif: Use dma_request_chan() instead dma_request_slave

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Date:   Tue, 25 Feb 2020 13:07:49 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Peter Ujfalusi <peter.ujfalusi@...com>, mchehab@...nel.org,
        rashanmu@...il.com, geert@...ux-m68k.org
Cc:     vkoul@...nel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2] media: rcar_drif: Use dma_request_chan() instead
 dma_request_slave_channel()

Hi Peter,

On 1/20/20 1:47 PM, Peter Ujfalusi wrote:
> dma_request_slave_channel() is a wrapper on top of dma_request_chan()
> eating up the error code.
> 
> By using dma_request_chan() directly the driver can support deferred
> probing against DMA.
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

Unfortunately the v1 version of this patch got merged, so can you make a
new patch against the current media_tree master to bring it up to date
with this v3?

My apologies for this.

Regards,

	Hans

> ---
> Hi,
> 
> Changes since v2:
> - Use %pe to print error name using the ch->dmach pointer
> - Set ch->dmach to NULL in case of error
> 
> Changes since v1:
> - Do not print error in case of EPROBE_DEFER
> - Added Reviewed-by from Geert
> 
> Regards,
> Peter
> 
>  drivers/media/platform/rcar_drif.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/platform/rcar_drif.c b/drivers/media/platform/rcar_drif.c
> index 0f267a237b42..3d2451ac347d 100644
> --- a/drivers/media/platform/rcar_drif.c
> +++ b/drivers/media/platform/rcar_drif.c
> @@ -275,10 +275,14 @@ static int rcar_drif_alloc_dmachannels(struct rcar_drif_sdr *sdr)
>  	for_each_rcar_drif_channel(i, &sdr->cur_ch_mask) {
>  		struct rcar_drif *ch = sdr->ch[i];
>  
> -		ch->dmach = dma_request_slave_channel(&ch->pdev->dev, "rx");
> -		if (!ch->dmach) {
> -			rdrif_err(sdr, "ch%u: dma channel req failed\n", i);
> -			ret = -ENODEV;
> +		ch->dmach = dma_request_chan(&ch->pdev->dev, "rx");
> +		if (IS_ERR(ch->dmach)) {
> +			ret = PTR_ERR(ch->dmach);
> +			if (ret != -EPROBE_DEFER)
> +				rdrif_err(sdr,
> +					  "ch%u: dma channel req failed: %pe\n",
> +					  i, ch->dmach);
> +			ch->dmach = NULL;
>  			goto dmach_error;
>  		}
>  
>