linux-kernel - Re: [PATCH] dma: Revert "dmaengine: mic_x100: add missing spin

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Date:	Wed, 23 Dec 2015 11:15:31 +0530
From:	Saurabh Sengar <saurabh.truth@...il.com>
To:	Ashutosh Dixit <ashutosh.dixit@...el.com>
Cc:	Vinod Koul <vinod.koul@...el.com>, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org, Sudeep Dutt <sudeep.dutt@...el.com>,
	Nikhil Rao <nikhil.rao@...el.com>,
	Siva Yerramreddy <yshivakrishna@...il.com>
Subject: Re: [PATCH] dma: Revert "dmaengine: mic_x100: add missing spin_unlock"

On 23 December 2015 at 09:05, Ashutosh Dixit <ashutosh.dixit@...el.com> wrote:
> This reverts commit e958e079e254 ("dmaengine: mic_x100: add missing
> spin_unlock").
>
> The above patch is incorrect. There is nothing wrong with the original
> code. The spin_lock is acquired in the "prep" functions and released
> in "submit".

Hi Ashutosh,

If it is need to be released by submit function, we don't require the
spin_unlock on success case as well.
am I correct ?

> Signed-off-by: Ashutosh Dixit <ashutosh.dixit@...el.com>
> ---
>  drivers/dma/mic_x100_dma.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/dma/mic_x100_dma.c b/drivers/dma/mic_x100_dma.c
> index cddfa8d..068e920 100644
> --- a/drivers/dma/mic_x100_dma.c
> +++ b/drivers/dma/mic_x100_dma.c
> @@ -317,7 +317,6 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
>         struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
>         struct device *dev = mic_dma_ch_to_device(mic_ch);
>         int result;
> -       struct dma_async_tx_descriptor *tx = NULL;
>
>         if (!len && !flags)
>                 return NULL;
> @@ -325,13 +324,10 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
>         spin_lock(&mic_ch->prep_lock);
>         result = mic_dma_do_dma(mic_ch, flags, dma_src, dma_dest, len);
>         if (result >= 0)
> -               tx = allocate_tx(mic_ch);
> -
> -       if (!tx)
> -               dev_err(dev, "Error enqueueing dma, error=%d\n", result);
> -
> +               return allocate_tx(mic_ch);
> +       dev_err(dev, "Error enqueueing dma, error=%d\n", result);
>         spin_unlock(&mic_ch->prep_lock);

This spin_unlock shouldn't be required as explained it is getting
released by submit function

> -       return tx;
> +       return NULL;
>  }
>
>  static struct dma_async_tx_descriptor *
> @@ -339,14 +335,13 @@ mic_dma_prep_interrupt_lock(struct dma_chan *ch, unsigned long flags)
>  {
>         struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
>         int ret;
> -       struct dma_async_tx_descriptor *tx = NULL;
>
>         spin_lock(&mic_ch->prep_lock);
>         ret = mic_dma_do_dma(mic_ch, flags, 0, 0, 0);
>         if (!ret)
> -               tx = allocate_tx(mic_ch);
> +               return allocate_tx(mic_ch);
>         spin_unlock(&mic_ch->prep_lock);

and this too ?

> -       return tx;
> +       return NULL;
>  }
>
>  /* Return the status of the transaction */
> --
> 2.0.0.rc3.2.g998f840
>
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