linux-kernel - Re: [PATCH RFC v3 1/5] dma: mpc512x: reorder mpc8308 specific instructions

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Date:	Sat, 3 Aug 2013 18:06:28 +0200
From:	Gerhard Sittig <gsi@...x.de>
To:	Alexander Popov <a13xp0p0v88@...il.com>
Cc:	Vinod Koul <vinod.koul@...el.com>, Dan Williams <djbw@...com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Arnd Bergmann <arnd@...db.de>,
	Anatolij Gustschin <agust@...x.de>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v3 1/5] dma: mpc512x: reorder mpc8308 specific
 instructions

On Wed, Jul 31, 2013 at 11:20 +0400, Alexander Popov wrote:
> 
> From: Gerhard Sittig <gsi@...x.de>
> 
> Concentrate the test and the specific code for MPC8308
> in the 'if' branch and handle MPC512x in the 'else' branch.
> 
> This modification only reorders instructions but doesn't change behaviour.
> 
> Signed-off-by: Alexander Popov <a13xp0p0v88@...il.com>
> ---
>  drivers/dma/mpc512x_dma.c | 42 +++++++++++++++++++++++++-----------------
>  1 file changed, 25 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/dma/mpc512x_dma.c b/drivers/dma/mpc512x_dma.c
> index 2d95673..b8881de 100644
> --- a/drivers/dma/mpc512x_dma.c
> +++ b/drivers/dma/mpc512x_dma.c
> @@ -50,9 +50,17 @@
>  #define MPC_DMA_DESCRIPTORS	64
>  
>  /* Macro definitions */
> -#define MPC_DMA_CHANNELS	64
>  #define MPC_DMA_TCD_OFFSET	0x1000
>  
> +/*
> + * Maximum channel counts for individual hardware variants
> + * and the maximum channel count over all supported controllers,
> + * used for data structure size
> + */
> +#define MPC8308_DMACHAN_MAX	16
> +#define MPC512x_DMACHAN_MAX	64
> +#define MPC_DMA_CHANNELS	64
> +
>  /* Arbitration mode of group and channel */
>  #define MPC_DMA_DMACR_EDCG	(1 << 31)
>  #define MPC_DMA_DMACR_ERGA	(1 << 3)

nit:  That's not what I wrote.  Please make sure to either cite
properly or to properly mark changes as such.  Don't spread false
information, please.  You are free to change what I submitted,
but you should not pretend that I wrote what has become of the
code after you have modified it.  Please fix the attribution.

Just to clarify:  The defines here appear to be more appropriate
than the initial enums, after it turned out that we need not
handle indiviudal channels in special ways, and really only need
these three numbers (one of them being the maximum of the
others).  But regardless of what you have changed, you should
clearly state the fact.

> @@ -716,10 +724,10 @@ static int mpc_dma_probe(struct platform_device *op)
>  
>  	dma = &mdma->dma;
>  	dma->dev = dev;
> -	if (!mdma->is_mpc8308)
> -		dma->chancnt = MPC_DMA_CHANNELS;
> +	if (mdma->is_mpc8308)
> +		dma->chancnt = MPC8308_DMACHAN_MAX;
>  	else
> -		dma->chancnt = 16; /* MPC8308 DMA has only 16 channels */
> +		dma->chancnt = MPC512x_DMACHAN_MAX;
>  	dma->device_alloc_chan_resources = mpc_dma_alloc_chan_resources;
>  	dma->device_free_chan_resources = mpc_dma_free_chan_resources;
>  	dma->device_issue_pending = mpc_dma_issue_pending;
> @@ -753,7 +761,19 @@ static int mpc_dma_probe(struct platform_device *op)
>  	 * - Round-robin group arbitration,
>  	 * - Round-robin channel arbitration.
>  	 */
> -	if (!mdma->is_mpc8308) {
> +	if (mdma->is_mpc8308) {
> +		/* MPC8308 has 16 channels and lacks some registers */
> +		out_be32(&mdma->regs->dmacr, MPC_DMA_DMACR_ERCA);
> +
> +		/* enable snooping */
> +		out_be32(&mdma->regs->dmagpor, MPC_DMA_DMAGPOR_SNOOP_ENABLE);
> +		/* Disable error interrupts */
> +		out_be32(&mdma->regs->dmaeeil, 0);
> +
> +		/* Clear interrupts status */
> +		out_be32(&mdma->regs->dmaintl, 0xFFFF);
> +		out_be32(&mdma->regs->dmaerrl, 0xFFFF);
> +	} else {
>  		out_be32(&mdma->regs->dmacr, MPC_DMA_DMACR_EDCG |
>  					MPC_DMA_DMACR_ERGA | MPC_DMA_DMACR_ERCA);
>  
> @@ -774,18 +794,6 @@ static int mpc_dma_probe(struct platform_device *op)
>  		/* Route interrupts to IPIC */
>  		out_be32(&mdma->regs->dmaihsa, 0);
>  		out_be32(&mdma->regs->dmailsa, 0);
> -	} else {
> -		/* MPC8308 has 16 channels and lacks some registers */
> -		out_be32(&mdma->regs->dmacr, MPC_DMA_DMACR_ERCA);
> -
> -		/* enable snooping */
> -		out_be32(&mdma->regs->dmagpor, MPC_DMA_DMAGPOR_SNOOP_ENABLE);
> -		/* Disable error interrupts */
> -		out_be32(&mdma->regs->dmaeeil, 0);
> -
> -		/* Clear interrupts status */
> -		out_be32(&mdma->regs->dmaintl, 0xFFFF);
> -		out_be32(&mdma->regs->dmaerrl, 0xFFFF);
>  	}
>  
>  	/* Register DMA engine */
> -- 
> 1.7.11.3


virtually yours
Gerhard Sittig
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