linux-kernel - Re: [PATCH] mmc: omap: Use dma_request

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Date:	Wed, 4 May 2016 09:32:02 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Peter Ujfalusi <peter.ujfalusi@...com>
Cc:	Kishon <kishon@...com>, Tony Lindgren <tony@...mide.com>,
	Roger Quadros <rogerq@...com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	linux-omap <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: omap: Use dma_request_chan() for requesting DMA channel

On 4 May 2016 at 05:59, Peter Ujfalusi <peter.ujfalusi@...com> wrote:
> On 05/03/2016 11:00 PM, Peter Ujfalusi wrote:
>>>> @@ -1382,29 +1379,31 @@ static int mmc_omap_probe(struct platform_device *pdev)
>>>>                 goto err_free_iclk;
>>>>         }
>>>>
>>>> -       dma_cap_zero(mask);
>>>> -       dma_cap_set(DMA_SLAVE, mask);
>>>> -
>>>>         host->dma_tx_burst = -1;
>>>>         host->dma_rx_burst = -1;
>>>>
>>>> -       res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "tx");
>>>> -       if (res)
>>>> -               sig = res->start;
>>>> -       host->dma_tx = dma_request_slave_channel_compat(mask,
>>>> -                               omap_dma_filter_fn, &sig, &pdev->dev, "tx");
>>>> -       if (!host->dma_tx)
>>>> -               dev_warn(host->dev, "unable to obtain TX DMA engine channel %u\n",
>>>> -                       sig);
>>>> -
>>>> -       res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "rx");
>>>> -       if (res)
>>>> -               sig = res->start;
>>>> -       host->dma_rx = dma_request_slave_channel_compat(mask,
>>>> -                               omap_dma_filter_fn, &sig, &pdev->dev, "rx");
>>>> -       if (!host->dma_rx)
>>>> -               dev_warn(host->dev, "unable to obtain RX DMA engine channel %u\n",
>>>> -                       sig);
>>>> +       host->dma_tx = dma_request_chan(&pdev->dev, "tx");
>>>> +       if (IS_ERR(host->dma_tx)) {
>>>> +               ret = PTR_ERR(host->dma_tx);
>>>> +               if (ret == -EPROBE_DEFER)
>>>> +                       goto err_free_iclk;
>>
>> and one clk_put(host->fclk) is missing from here.
>>
>>>> +
>>>> +               host->dma_tx = NULL;
>>>
>>> Instead of setting this to NULL, let's keep its value and later check
>>> it with IS_ERR() when needed.
>>
>> I thought about it, but decided against without need to have changes in other
>> places in the driver.
>
> This sentence does not make too much sense ;) Let's try it again:
> So, I have considered to use PTR_ERR in the driver for the DMA channel, but I
> wanted to avoid too broad changes in the driver. Keeping the ERR_PTR would
> bring no runtime benefit since we only care if we have channel or not.

Okay, so let's deal with that separately instead then.

Kind regards
Uffe