linux-kernel - Re: [RFC PATCH 2/3] ata: ahci-platform: Add ports-implemented dt bindings.

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Date:	Tue, 29 Mar 2016 09:11:32 -0500
From:	Rob Herring <robh+dt@...nel.org>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:	Tejun Heo <tj@...nel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	Andy Gross <andy.gross@...aro.org>,
	Hans de Goede <hdegoede@...hat.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	linux-soc@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, jmaggard10@...il.com
Subject: Re: [RFC PATCH 2/3] ata: ahci-platform: Add ports-implemented dt bindings.

On Tue, Mar 29, 2016 at 8:11 AM, Srinivas Kandagatla
<srinivas.kandagatla@...aro.org> wrote:
> On some SOCs PORTS_IMPL register value is never programmed by the BIOS

s/BIOS/firmware/

You do plan to fix this in your firmware/bootloader, too, right?

> and left at zero value. Which means that no sata ports are avaiable for
> software. AHCI driver used to cope up with this by fabricating the
> port_map if the PORTS_IMPL register is read zero, but recent patch
> broke this workaround as zero value was valid for nvme disks.

s/nvme/NVMe/

>
> This patch adds ports-implemented dt bindings as workaround for this issue

s/dt/DT/

> in a way that DT can dictate the port_map incase where the SOCs does not
> program it already.

port_map is a Linux term.

...can override the PORTS_IMPL register in cases where the firmware
did not program it already.

>
> Fixes: 566d1827df2e ("libata: disable forced PORTS_IMPL for >= AHCI 1.3)
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  Documentation/devicetree/bindings/ata/ahci-platform.txt | 11 +++++++++++
>  drivers/ata/ahci_platform.c                             |  4 ++++
>  2 files changed, 15 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/ata/ahci-platform.txt b/Documentation/devicetree/bindings/ata/ahci-platform.txt
> index 30df832..8165db3 100644
> --- a/Documentation/devicetree/bindings/ata/ahci-platform.txt
> +++ b/Documentation/devicetree/bindings/ata/ahci-platform.txt
> @@ -32,6 +32,10 @@ Optional properties:
>  - target-supply     : regulator for SATA target power
>  - phys              : reference to the SATA PHY node
>  - phy-names         : must be "sata-phy"
> +- ports-implemented : Mask that indicates which ports that the HBA supports
> +                     are available for software to use. Useful if PORTS_IMPL
> +                     is not programmed by the BIOS, which is true with
> +                     some embedded SOC's.
>
>  Required properties when using sub-nodes:
>  - #address-cells    : number of cells to encode an address
> @@ -59,6 +63,13 @@ Examples:
>                 target-supply = <&reg_ahci_5v>;
>         };
>
> +       sata0: sata@...00000 { /* Qualcomm APQ8064 */

Do you really need another example just for this?

> +               compatible = "generic-ahci";

Where's your chip specific compatible string? You would not require a
DT update to fix this if you had that.

> +               reg = <0x29000000 0x180>;
> +               interrupts = <GIC_SPI 209 IRQ_TYPE_NONE>;
> +               ports-implemented = <0x1>;
> +       };
> +
>  With sub-nodes:
>         sata@...90000 {
>                 compatible = "marvell,berlin2q-achi", "generic-ahci";
> diff --git a/drivers/ata/ahci_platform.c b/drivers/ata/ahci_platform.c
> index 4044233..ec8db80 100644
> --- a/drivers/ata/ahci_platform.c
> +++ b/drivers/ata/ahci_platform.c
> @@ -42,6 +42,7 @@ static int ahci_probe(struct platform_device *pdev)
>         struct device *dev = &pdev->dev;
>         struct ahci_host_priv *hpriv;
>         int rc;
> +       u32 ports_impl;
>
>         hpriv = ahci_platform_get_resources(pdev);
>         if (IS_ERR(hpriv))
> @@ -51,6 +52,9 @@ static int ahci_probe(struct platform_device *pdev)
>         if (rc)
>                 return rc;
>
> +       of_property_read_u32(dev->of_node,
> +                            "ports-implemented", &hpriv->force_port_map);
> +
>         if (of_device_is_compatible(dev->of_node, "hisilicon,hisi-ahci"))
>                 hpriv->flags |= AHCI_HFLAG_NO_FBS | AHCI_HFLAG_NO_NCQ;
>
> --
> 2.5.0
>