Re: [PATCH v6 8/8] usb: ehci-exynos: Change to use phy provided by the generic phy framework

From: Tomasz Figa
Date: Mon Mar 03 2014 - 09:37:55 EST



On 05.02.2014 18:30, Olof Johansson wrote:
On Wed, Feb 5, 2014 at 7:57 AM, Kamil Debski <k.debski@xxxxxxxxxxx> wrote:
Hi Olof,

Thank you for your review.

From: Olof Johansson [mailto:olof@xxxxxxxxx]
Sent: Wednesday, January 29, 2014 9:55 PM

Hi,

On Wed, Jan 29, 2014 at 9:29 AM, Kamil Debski <k.debski@xxxxxxxxxxx>
wrote:
Change the phy provider used from the old one using the USB phy
framework to a new one using the Generic phy framework.

Signed-off-by: Kamil Debski <k.debski@xxxxxxxxxxx>
---
.../devicetree/bindings/usb/exynos-usb.txt | 13 +++
drivers/usb/host/ehci-exynos.c | 97
+++++++++++++-------
2 files changed, 76 insertions(+), 34 deletions(-)

diff --git a/Documentation/devicetree/bindings/usb/exynos-usb.txt
b/Documentation/devicetree/bindings/usb/exynos-usb.txt
index d967ba1..25e199a 100644
--- a/Documentation/devicetree/bindings/usb/exynos-usb.txt
+++ b/Documentation/devicetree/bindings/usb/exynos-usb.txt
@@ -12,6 +12,10 @@ Required properties:
- interrupts: interrupt number to the cpu.
- clocks: from common clock binding: handle to usb clock.
- clock-names: from common clock binding: Shall be "usbhost".
+ - port: if in the SoC there are EHCI phys, they should be listed
here.
+One phy per port. Each port should have its reg entry with a
+consecutive number. Also it should contain phys and phy-names
entries
+specifying the phy used by the port.

Optional properties:
- samsung,vbus-gpio: if present, specifies the GPIO that @@ -27,6
+31,15 @@ Example:

clocks = <&clock 285>;
clock-names = "usbhost";
+
+ #address-cells = <1>;
+ #size-cells = <0>;
+ port@0 {
+ reg = <0>;
+ phys = <&usb2phy 1>;
+ phy-names = "host";
+ status = "disabled";
+ };
};

OHCI

[...]

@@ -102,14 +132,26 @@ static int exynos_ehci_probe(struct
platform_device *pdev)
"samsung,exynos5440-ehci"))
goto skip_phy;

- phy = devm_usb_get_phy(&pdev->dev, USB_PHY_TYPE_USB2);
- if (IS_ERR(phy)) {
- usb_put_hcd(hcd);
- dev_warn(&pdev->dev, "no platform data or transceiver
defined\n");
- return -EPROBE_DEFER;
- } else {
- exynos_ehci->phy = phy;
- exynos_ehci->otg = phy->otg;
+ for_each_available_child_of_node(pdev->dev.of_node, child) {
+ err = of_property_read_u32(child, "reg",
&phy_number);
+ if (err) {
+ dev_err(&pdev->dev, "Failed to parse device
tree\n");
+ of_node_put(child);
+ return err;
+ }
+ if (phy_number >= PHY_NUMBER) {
+ dev_err(&pdev->dev, "Failed to parse device
tree - number out of range\n");
+ of_node_put(child);
+ return -EINVAL;
+ }
+ phy = devm_of_phy_get(&pdev->dev, child, 0);
+ of_node_put(child);
+ if (IS_ERR(phy)) {
+ dev_err(&pdev->dev, "Failed to get phy number
%d",
+
phy_number);
+ return PTR_ERR(phy);
+ }
+ exynos_ehci->phy[phy_number] = phy;

this looks like it is now breaking older device trees, where ports
might not be described. Since device tree interfaces need to be
backwards compatible, you still need to handle the old case of not
having ports described.

There are two ways of doing this:

1. Fall back to the old behavior if there are no ports 2. Use a new
compatible value for the new model with port subnodes, and if the old
compatible value is used, then fall back to the old behavior.

I'm guessing (1) might be easiest since you can check for the presence
of #address-cells to tell if this is just an old style node, or if it's
a new-style node without any ports below it.

The ultimate goal is to remove the old phy driver. Unfortunately
this has to be synced with the new USB3 phy driver by Vivek Gautam. I think
he
is also close to completion. What about this case? In the end the old driver
will be removed and no longer be supported. Having backward compatibility in
mind, it is possible to have the old and the new phy driver together in one
kernel release. But do we want to have two drivers doing the same thing at
the same time?

It is mostly irrelevant if there is a new driver or not -- the old
device tree has to keep working. In this case it would mean that the
new driver needs to work with older device trees as well, or people
will see functionality regressing.

The device tree is a description of the hardware, not an extension of
the driver.

The problem with this case is that when the original driver was added there was no way to bind PHY providers and consumers together.

Basically there was no generic PHY subsystem. Instead the hacky USB PHY subsystem was used with hardcoded PHY IDs (types) in both PHY driver and user drivers. In DT you only had nodes for the PHY controller and consumer IPs (e.g. EHCI, HSOTG), but no relation between them.

This was broken, merged without proper review and I don't think we should be supporting this, along with a lot of completely messed up bindings we were supposed to fix after a lot of discussion that happened last year, but I haven't seen much movement in this direction, instead ending with such FUBDs being stable and a need to maintain support for them...

Best regards,
Tomasz
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