linux-kernel - Re: [PATCH 1/3] RFC: AHCI: libahci is missing DMA

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Message-ID: <20131204123234.GC3158@htj.dyndns.org>
Date:	Wed, 4 Dec 2013 07:32:34 -0500
From:	Tejun Heo <tj@...nel.org>
To:	oliver@...inagl.nl
Cc:	grant.likely@...aro.org, ob.herring@...xeda.com,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, dev@...ux-sunxi.org,
	maxime.ripard@...e-electrons.com, ijc@...lion.org.uk,
	hdegoede@...hat.com, oliver+list@...inagl.nl
Subject: Re: [PATCH 1/3] RFC: AHCI: libahci is missing DMA

On Wed, Dec 04, 2013 at 01:10:53PM +0100, oliver@...inagl.nl wrote:
> From: Oliver Schinagl <oliver@...inagl.nl>
> 
> The Allwinner sunxi platforms have patched in the following to enable
> DMA. This patch enables DMA controllers for the SUNXI Architecture.
> 
> Signed-off-by: Olliver Schinagl <oliver@...inagl.nl>
> ---
>  drivers/ata/ahci.h    | 6 ++++++
>  drivers/ata/libahci.c | 8 ++++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
> index 2289efdf..2bf2423 100644
> --- a/drivers/ata/ahci.h
> +++ b/drivers/ata/ahci.h
> @@ -138,6 +138,7 @@ enum {
>  	PORT_SCR_NTF		= 0x3c, /* SATA phy register: SNotification */
>  	PORT_FBS		= 0x40, /* FIS-based Switching */
>  	PORT_DEVSLP		= 0x44, /* device sleep */
> +	PORT_DMA		= 0x70, /* direct memory access */
>  
>  	/* PORT_IRQ_{STAT,MASK} bits */
>  	PORT_IRQ_COLD_PRES	= (1 << 31), /* cold presence detect */
> @@ -209,6 +210,11 @@ enum {
>  	PORT_DEVSLP_DSP		= (1 << 1),       /* DevSlp present */
>  	PORT_DEVSLP_ADSE	= (1 << 0),       /* Aggressive DevSlp enable */
>  
> +	/* PORT_DMA bits */
> +	PORT_DMA_SETUP_OFFSET	= 8, /* dma setup offset */
> +	PORT_DMA_SETUP_MASK	= (0xff << PORT_DMA_SETUP_OFFSET),/* dma mask */
> +	PORT_DMA_SETUP_INIT	= (0x44 << 0),

Ummm... this doesn't belong to ahci proper, right?

> +
>  	/* hpriv->flags bits */
>  
>  #define AHCI_HFLAGS(flags)		.private_data	= (void *)(flags)
> diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
> index c482f8c..d697a74 100644
> --- a/drivers/ata/libahci.c
> +++ b/drivers/ata/libahci.c
> @@ -570,6 +570,14 @@ void ahci_start_engine(struct ata_port *ap)
>  	void __iomem *port_mmio = ahci_port_base(ap);
>  	u32 tmp;
>  
> +#ifdef CONFIG_ARCH_SUNXI
> +	/* Setup DMA before DMA start */
> +	tmp = readl(port_mmio + PORT_DMA);
> +	tmp &= ~PORT_DMA_SETUP_MASK;
> +	tmp |= PORT_DMA_SETUP_INIT << PORT_DMA_SETUP_OFFSET;
> +	writel(tmp, port_mmio + PORT_DMA);
> +#endif

If this is something platform device specific, wouldn't overriding
->port_start() which wraps around ahci_port_start() make more sense?

Thanks.

-- 
tejun
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