linux-kernel - Re: [PATCH] pch_dma: Fix CTL register access issue

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Message-ID: <1311603829.8206.13.camel@vkoul-mobl4>
Date:	Mon, 25 Jul 2011 19:53:49 +0530
From:	Vinod Koul <vkoul@...radead.org>
To:	Tomoya MORINAGA <tomoya-linux@....okisemi.com>
Cc:	vinod.koul@...el.com, Dan Williams <dan.j.williams@...el.com>,
	linux-kernel@...r.kernel.org, qi.wang@...el.com,
	yong.y.wang@...el.com, joel.clark@...el.com,
	kok.howg.ewe@...el.com, toshiharu-linux@....okisemi.com
Subject: Re: [PATCH] pch_dma: Fix CTL register access issue

On Thu, 2011-07-14 at 09:52 +0900, Tomoya MORINAGA wrote:
> Currently, Mode-Control register is accessed by read-modify-write.
> 
> According to DMA hardware specifications datasheet, prohibits this method.
> Because this register resets to 0 by DMA HW after DMA transfer completes.
> Thus, current read-modify-write processing can cause unexpected behavior.
> 
> The datasheet says in case of writing Mode-Control register, set the value for only target channel, the others must set '11b'.
> e.g. Set DMA0=01b  DMA11=10b
> CTL0=33333331h
> CTL2=00002333h
> 
> NOTE:
> CTL0 includes DMA0~7 Mode-Control register.
> CTL2 includes DMA8~11 Mode-Control register.
> 
> This patch modifies the issue.
> 
> Signed-off-by: Tomoya MORINAGA <tomoya-linux@....okisemi.com>
> ---
>  drivers/dma/pch_dma.c |   42 +++++++++++++++++++++++++++++++-----------
>  1 files changed, 31 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/dma/pch_dma.c b/drivers/dma/pch_dma.c
> index 9dc92de..7460490 100644
> --- a/drivers/dma/pch_dma.c
> +++ b/drivers/dma/pch_dma.c
> @@ -62,6 +62,9 @@
>  
>  #define MAX_CHAN_NR			8
>  
> +#define DMA_MASK_CTL0_MODE	0x33333333
> +#define DMA_MASK_CTL2_MODE	0x00003333
> +
>  static unsigned int init_nr_desc_per_channel = 64;
>  module_param(init_nr_desc_per_channel, uint, 0644);
>  MODULE_PARM_DESC(init_nr_desc_per_channel,
> @@ -210,10 +213,17 @@ static void pdc_set_dir(struct dma_chan *chan)
>  	struct pch_dma_chan *pd_chan = to_pd_chan(chan);
>  	struct pch_dma *pd = to_pd(chan->device);
>  	u32 val;
> +	u32 mask_mode;
> +	u32 mask_ctl;
>  
>  	if (chan->chan_id < 8) {
>  		val = dma_readl(pd, CTL0);
>  
> +		mask_mode = DMA_CTL0_MODE_MASK_BITS <<
> +					(DMA_CTL0_BITS_PER_CH * chan->chan_id);
> +		mask_ctl = DMA_MASK_CTL0_MODE & ~(DMA_CTL0_MODE_MASK_BITS <<
> +				       (DMA_CTL0_BITS_PER_CH * chan->chan_id));
> +		val &= mask_mode;
>  		if (pd_chan->dir == DMA_TO_DEVICE)
>  			val |= 0x1 << (DMA_CTL0_BITS_PER_CH * chan->chan_id +
>  				       DMA_CTL0_DIR_SHIFT_BITS);
> @@ -221,18 +231,24 @@ static void pdc_set_dir(struct dma_chan *chan)
>  			val &= ~(0x1 << (DMA_CTL0_BITS_PER_CH * chan->chan_id +
>  					 DMA_CTL0_DIR_SHIFT_BITS));
>  
> +		val |= mask_ctl;
>  		dma_writel(pd, CTL0, val);
>  	} else {
>  		int ch = chan->chan_id - 8; /* ch8-->0 ch9-->1 ... ch11->3 */
>  		val = dma_readl(pd, CTL3);
>  
> +		mask_mode = DMA_CTL0_MODE_MASK_BITS <<
> +						(DMA_CTL0_BITS_PER_CH * ch);
> +		mask_ctl = DMA_MASK_CTL2_MODE & ~(DMA_CTL0_MODE_MASK_BITS <<
> +						 (DMA_CTL0_BITS_PER_CH * ch));
> +		val &= mask_mode;
>  		if (pd_chan->dir == DMA_TO_DEVICE)
>  			val |= 0x1 << (DMA_CTL0_BITS_PER_CH * ch +
>  				       DMA_CTL0_DIR_SHIFT_BITS);
>  		else
>  			val &= ~(0x1 << (DMA_CTL0_BITS_PER_CH * ch +
>  					 DMA_CTL0_DIR_SHIFT_BITS));
> -
> +		val |= mask_ctl;
>  		dma_writel(pd, CTL3, val);
>  	}
>  
> @@ -244,26 +260,30 @@ static void pdc_set_mode(struct dma_chan *chan, u32 mode)
>  {
>  	struct pch_dma *pd = to_pd(chan->device);
>  	u32 val;
> +	u32 mask_ctl;
> +	u32 mask_dir;
>  
>  	if (chan->chan_id < 8) {
> +		mask_ctl = DMA_MASK_CTL0_MODE & ~(DMA_CTL0_MODE_MASK_BITS <<
> +			   (DMA_CTL0_BITS_PER_CH * chan->chan_id));
> +		mask_dir = 1 << (DMA_CTL0_BITS_PER_CH * chan->chan_id +\
> +				 DMA_CTL0_DIR_SHIFT_BITS);
>  		val = dma_readl(pd, CTL0);
> -
> -		val &= ~(DMA_CTL0_MODE_MASK_BITS <<
> -			(DMA_CTL0_BITS_PER_CH * chan->chan_id));
> +		val &= mask_dir;
>  		val |= mode << (DMA_CTL0_BITS_PER_CH * chan->chan_id);
> -
> +		val |= mask_ctl;
>  		dma_writel(pd, CTL0, val);
>  	} else {
>  		int ch = chan->chan_id - 8; /* ch8-->0 ch9-->1 ... ch11->3 */
> -
> +		mask_ctl = DMA_MASK_CTL2_MODE & ~(DMA_CTL0_MODE_MASK_BITS <<
> +						 (DMA_CTL0_BITS_PER_CH * ch));
> +		mask_dir = 1 << (DMA_CTL0_BITS_PER_CH * ch +\
> +				 DMA_CTL0_DIR_SHIFT_BITS);
>  		val = dma_readl(pd, CTL3);
> -
> -		val &= ~(DMA_CTL0_MODE_MASK_BITS <<
> -			(DMA_CTL0_BITS_PER_CH * ch));
> +		val &= mask_dir;
>  		val |= mode << (DMA_CTL0_BITS_PER_CH * ch);
> -
> +		val |= mask_ctl;
>  		dma_writel(pd, CTL3, val);
> -
>  	}
>  
>  	dev_dbg(chan2dev(chan), "pdc_set_mode: chan %d -> %x\n",
> -- 
> 1.7.4.4
APPLIED, Thanks

-- 
~Vinod Koul
Intel Corp.

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