linux-kernel - Re: [PATCH v2 4/4] dmaengine: xilinx_vdma: Improve channel idle checking

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Message-ID: <20160223031130.GI17690@localhost>
Date:	Tue, 23 Feb 2016 08:41:30 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Kedareswara rao Appana <appana.durga.rao@...inx.com>
Cc:	dan.j.williams@...el.com, michal.simek@...inx.com,
	soren.brinkmann@...inx.com, appanad@...inx.com,
	moritz.fischer@...us.com, laurent.pinchart@...asonboard.com,
	luis@...ethencourt.com, anirudh@...inx.com,
	dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] dmaengine: xilinx_vdma: Improve channel idle
 checking

On Mon, Feb 22, 2016 at 11:24:37AM +0530, Kedareswara rao Appana wrote:
> This patch improves the channel idle cheking by introduing
				      ^^^^^^^^^
typo

> a new varibale in chan private structure.
	^^^^^^^
here too :(

and there is no description how this improvement is achieved and why
> 
> Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
> ---
> Changes for v2:
> ---> splitted the changes into multiple patches.
> 
>  drivers/dma/xilinx/xilinx_vdma.c | 41 ++++++++--------------------------------
>  1 file changed, 8 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/dma/xilinx/xilinx_vdma.c b/drivers/dma/xilinx/xilinx_vdma.c
> index 8db07f7..51686d1 100644
> --- a/drivers/dma/xilinx/xilinx_vdma.c
> +++ b/drivers/dma/xilinx/xilinx_vdma.c
> @@ -202,6 +202,7 @@ struct xilinx_vdma_tx_descriptor {
>   * @has_sg: Support scatter transfers
>   * @genlock: Support genlock mode
>   * @err: Channel has errors
> + * @idle: Check for channel idle
>   * @tasklet: Cleanup work after irq
>   * @config: Device configuration info
>   * @flush_on_fsync: Flush on Frame sync
> @@ -225,6 +226,7 @@ struct xilinx_vdma_chan {
>  	bool has_sg;
>  	bool genlock;
>  	bool err;
> +	bool idle;
>  	struct tasklet_struct tasklet;
>  	struct xilinx_vdma_config config;
>  	bool flush_on_fsync;
> @@ -519,32 +521,6 @@ static enum dma_status xilinx_vdma_tx_status(struct dma_chan *dchan,
>  }
>  
>  /**
> - * xilinx_vdma_is_running - Check if VDMA channel is running
> - * @chan: Driver specific VDMA channel
> - *
> - * Return: '1' if running, '0' if not.
> - */
> -static bool xilinx_vdma_is_running(struct xilinx_vdma_chan *chan)
> -{
> -	return !(vdma_ctrl_read(chan, XILINX_VDMA_REG_DMASR) &
> -		 XILINX_VDMA_DMASR_HALTED) &&
> -		(vdma_ctrl_read(chan, XILINX_VDMA_REG_DMACR) &
> -		 XILINX_VDMA_DMACR_RUNSTOP);
> -}
> -
> -/**
> - * xilinx_vdma_is_idle - Check if VDMA channel is idle
> - * @chan: Driver specific VDMA channel
> - *
> - * Return: '1' if idle, '0' if not.
> - */
> -static bool xilinx_vdma_is_idle(struct xilinx_vdma_chan *chan)
> -{
> -	return vdma_ctrl_read(chan, XILINX_VDMA_REG_DMASR) &
> -		XILINX_VDMA_DMASR_IDLE;
> -}
> -
> -/**
>   * xilinx_vdma_halt - Halt VDMA channel
>   * @chan: Driver specific VDMA channel
>   */
> @@ -614,6 +590,9 @@ static void xilinx_vdma_start_transfer(struct xilinx_vdma_chan *chan)
>  	if (list_empty(&chan->pending_list))
>  		return;
>  
> +	if (!chan->idle)
> +		return;
> +
>  	desc = list_first_entry(&chan->pending_list,
>  				struct xilinx_vdma_tx_descriptor, node);
>  	tail_desc = list_last_entry(&chan->pending_list,
> @@ -622,13 +601,6 @@ static void xilinx_vdma_start_transfer(struct xilinx_vdma_chan *chan)
>  	tail_segment = list_last_entry(&tail_desc->segments,
>  				       struct xilinx_vdma_tx_segment, node);
>  
> -	/* If it is SG mode and hardware is busy, cannot submit */
> -	if (chan->has_sg && xilinx_vdma_is_running(chan) &&
> -	    !xilinx_vdma_is_idle(chan)) {
> -		dev_dbg(chan->dev, "DMA controller still busy\n");
> -		return;
> -	}
> -
>  	/*
>  	 * If hardware is idle, then all descriptors on the running lists are
>  	 * done, start new transfers
> @@ -708,6 +680,7 @@ static void xilinx_vdma_start_transfer(struct xilinx_vdma_chan *chan)
>  
>  	list_splice_tail_init(&chan->pending_list, &chan->active_list);
>  	chan->desc_pendingcount = 0;
> +	chan->idle = false;
>  }
>  
>  /**
> @@ -854,6 +827,7 @@ static irqreturn_t xilinx_vdma_irq_handler(int irq, void *data)
>  	if (status & XILINX_VDMA_DMASR_FRM_CNT_IRQ) {
>  		spin_lock(&chan->lock);
>  		xilinx_vdma_complete_descriptor(chan);
> +		chan->idle = true;
>  		xilinx_vdma_start_transfer(chan);
>  		spin_unlock(&chan->lock);
>  	}
> @@ -1212,6 +1186,7 @@ static int xilinx_vdma_chan_probe(struct xilinx_vdma_device *xdev,
>  
>  	list_add_tail(&chan->common.device_node, &xdev->common.channels);
>  	xdev->chan[chan->id] = chan;
> +	chan->idle = true;
>  
>  	/* Reset the channel */
>  	err = xilinx_vdma_chan_reset(chan);
> -- 
> 2.1.2
> 

-- 
~Vinod