Subject: [PATCH v2 2/4] ARM: sunxi: Add ahci-sunxi driver for the Allwinner SUNXi SoCs sata

From: [email-masked] (Hans de Goede)
Date: Sun, 05 Jan 2014 00:44:06 +0100

Hi,

On 01/04/2014 10:39 PM, Arnd Bergmann wrote:
> On Saturday 04 January 2014 10:14:36 Hans de Goede wrote:
>> diff --git a/Documentation/devicetree/bindings/ata/ahci-sunxi.txt b/Documentation/devicetree/bindings/ata/ahci-sunxi.txt
>> new file mode 100644
>> index 0000000..0792fa5
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/ata/ahci-sunxi.txt
>> @@ -0,0 +1,24 @@
>> +Allwinner SUNXI AHCI SATA Controller
>> +
>> +SATA nodes are defined to describe on-chip Serial ATA controllers.
>> +Each SATA controller should have its own node.
>> +
>> +Required properties:
>> +- compatible	: compatible list, contains "allwinner,sun4i-a10-ahci"
>> +- reg		: <registers mapping>
>> +- interrupts	: <interrupt mapping for AHCI IRQ>
>> +- clocks	: clocks for ACHI
>> +- clock-names	: clock names for AHCI
>
> The binding needs to specify the required names for the clocks.

Will fix.

>
>> +Optional properties:
>> +- pwr-supply	: regulator to control the power supply GPIO
>> +
>> +Example:
>> +	ahci at 01c18000 {
>> +		compatible = "allwinner,sun4i-a10-ahci";
>> +		reg = <0x01c18000 0x1000>;
>> +		interrupts = <0 56 1>;
>> +		clocks = <&ahb_gates 25>, <&pll6 0>;
>> +		clock-names = "ahb_sata", "pll6_sata";
>
> "pll6_sata" doesn't sound particularly generic. The name should
> reflect what the clock is used for, not what drives it.

Will change to ahb + sata_ref.

>
> Also, please send the binding as a separate patch with Cc to
> the devicetree-discuss mailing list.

Hmm, this contradicts what others are saying who have requested for
the binding docs to be part of the same commit as the driver (with
various other drivers). Note that I've cc-ed devicetree already.

>
>> +
>> +static int sunxi_ahci_phy_init(struct device *dev, void __iomem *reg_base)
>> +{
>> +	u32 reg_val;
>> +	int timeout;
>> +
>> +	/* This magic is from the original code */
>> +	writel(0, reg_base + AHCI_RWCR);
>> +	mdelay(5);
>
> This function should probably be in a separate phy driver.  I would
> very much hope that we can minimize the required code in an AHCI
> driver and move code from this new file into the ahci-platform
> driver. The clock, regulator and phy setup can all be optional
> properties of the generic driver, and then there shouldn't
> be much left that is sunxi specific.

Writing a phy driver, and extending ahci-platform to use that
was my original plan. But the phy really is part of the
ahci ip-block here, and not a separate ip-block. Its registers
are smack in the middle of the io-range for the ahci function.

Also note that sunxi_ahci_pre_start_engine is rather sunxi
specific. Needing to put that in a generic ahci_platform driver
and only activating it for sunxi socs would only serve to
prove my point that at some point it is simply easier and
better to write a non generic platform glue driver when dealing
with exotic ahci ip blocks.

If we end up putting all sort of if soca do foo else if socb
do bar, else do nothing magic in ahci_platform.c I think we're
over generalizing. If something nicely fits as a generic
platform dev, by all means we should use a generic platform
driver, but that just won't work cleanly here.

Actually I've just completed writing a phy driver for
the usbphy in the same soc, and a patch to extend ehci-platform
to take an optional clk and phy. So I completely agree with the
basic idea, it just does not seem doable cleanly in this case,
hence my choice to write a separate platform driver. For the
usb stuff (wip) see:
https://github.com/jwrdegoede/linux-sunxi/commit/4655dd01936f42d8a75da08a00af439e0a34eaf7
https://github.com/jwrdegoede/linux-sunxi/commit/bcb674859d015ff9e082829dbd5cf239b8b53d4a

As said this is exactly what your asking me to do for sunxi-ahci,
but the difference is that for sunxi-ehci it works nicely, and
for sunxi-ahci it just doesn't work cleanly.

>
>> +static int sunxi_ahci_susp(struct device *dev)
>> +{
>> +	struct ata_host *host = dev_get_drvdata(dev);
>> +	struct ahci_host_priv *hpriv = host->private_data;
>> +	struct sunxi_ahci *ahci = hpriv->plat_data;
>> +	int ret;
>> +
>> +	/*
>> +	 * AHCI spec rev1.1 section 8.3.3:
>> +	 * Software must disable interrupts prior to requesting a
>> +	 * transition of the HBA to D3 state.
>> +	 */
>> +	sunxi_clrbits(hpriv->mmio + HOST_CTL, HOST_IRQ_EN);
>> +
>> +	ret = ata_host_suspend(host, PMSG_SUSPEND);
>> +	if (ret)
>> +		return ret;
>> +
>> +	sunxi_ahci_disable_clks(ahci);
>> +
>> +	return 0;
>> +}
>
> The only thing in here that seems sunxi-specific is the irq disabling
> part. Can't you do this instead by calling disable_irq() and make
> the function completely generic?

The irq disabling part actually is not sunxi specific, ahci_platform.c
has it too.

Regards,

Hans