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

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Date:	Tue, 3 May 2016 23:00:47 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Ulf Hansson <ulf.hansson@...aro.org>
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 05/03/16 11:46, Ulf Hansson wrote:
> On 29 April 2016 at 15:06, Peter Ujfalusi <peter.ujfalusi@...com> 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.
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
>> CC: Ulf Hansson <ulf.hansson@...aro.org>
>> CC: Jarkko Nikula <jarkko.nikula@...mer.com>
>> ---
>>  drivers/mmc/host/omap.c | 45 ++++++++++++++++++++++-----------------------
>>  1 file changed, 22 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
>> index b9958a123594..a8d9228657b2 100644
>> --- a/drivers/mmc/host/omap.c
>> +++ b/drivers/mmc/host/omap.c
>> @@ -23,7 +23,6 @@
>>  #include <linux/spinlock.h>
>>  #include <linux/timer.h>
>>  #include <linux/of.h>
>> -#include <linux/omap-dma.h>
>>  #include <linux/mmc/host.h>
>>  #include <linux/mmc/card.h>
>>  #include <linux/mmc/mmc.h>
>> @@ -1321,8 +1320,6 @@ static int mmc_omap_probe(struct platform_device *pdev)
>>         struct omap_mmc_platform_data *pdata = pdev->dev.platform_data;
>>         struct mmc_omap_host *host = NULL;
>>         struct resource *res;
>> -       dma_cap_mask_t mask;
>> -       unsigned sig = 0;
>>         int i, ret = 0;
>>         int irq;
>>
>> @@ -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.

> 
>> +               dev_warn(host->dev, "TX DMA channel request failed\n");
>> +       }
>> +
>> +       host->dma_rx = dma_request_chan(&pdev->dev, "rx");
>> +       if (IS_ERR(host->dma_rx)) {
>> +               ret = PTR_ERR(host->dma_rx);
>> +               if (ret == -EPROBE_DEFER) {
>> +                       dma_release_channel(host->dma_tx);
> 
> host->dma_tx can be NULL here, so this isn't safe.

Oh, true.

> 
>> +                       clk_put(host->fclk);
>> +                       goto err_free_iclk;
>> +               }
>> +
>> +               host->dma_rx = NULL;
> 
> Instead of setting this to NULL, let's keep its value and later check
> it with IS_ERR() when needed.
> 
>> +               dev_warn(host->dev, "RX DMA channel request failed\n");
>> +       }
>>
>>         ret = request_irq(host->irq, mmc_omap_irq, 0, DRIVER_NAME, host);
>>         if (ret)
>> --
>> 2.8.1
>>
> 
> Kind regards
> Uffe
> 


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