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

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Date:	Wed, 04 Dec 2013 16:47:31 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	oliver@...inagl.nl, tj@...nel.org, 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
CC:	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

Hello.

On 04-12-2013 16:10, 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
[...]
> @@ -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),

    Why not shift it right by PORT_DMA_SETUP_OFFSET if you do it in the next 
file anyway?

[...]
> 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
> +

    I don't think #ifdef is appropriate here.

WBR, Sergei

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