Re: [PATCH v4 3/4] usb: ohci-exynos: Add facility to use phy provided by the generic phy framework

[Vivek Gautam]

Hi Tomasz,


On Thu, May 1, 2014 at 10:46 PM, Tomasz Figa <tomasz.figa@xxxxxxxxx> wrote:
> Hi Vivek,
>
> Please see my comments inline.

Thanks for the review, please find my answers inline.

>
>
> On 30.04.2014 07:19, Vivek Gautam wrote:
>>
>> Add support to consume phy provided by Generic phy framework.
>> Keeping the support for older usb-phy intact right now, in order
>> to prevent any functionality break in absence of relevant
>> device tree side change for ohci-exynos.
>> Once we move to new phy in the device nodes for ohci, we can
>> remove the support for older phys.
>>
>> Signed-off-by: Vivek Gautam <gautam.vivek@xxxxxxxxxxx>
>> Cc: Jingoo Han <jg1.han@xxxxxxxxxxx>
>> Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>> ---
>>
>> Changes from v3:
>>   - Calling usb_phy_shutdown() when exynos_ohci_phy_enable() is failing.
>>   - Made exynos_ohci_phy_disable() return void, since its return value
>>     did not serve any purpose.
>>   - Calling clk_disable_unprepare() in exynos_ohci_resume() when
>>     exynos_ohci_phy_enable() is failed.
>>
>>   .../devicetree/bindings/usb/exynos-usb.txt         |   19 +++
>>   drivers/usb/host/ohci-exynos.c                     |  128
>> +++++++++++++++++---
>>   2 files changed, 132 insertions(+), 15 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/usb/exynos-usb.txt
>> b/Documentation/devicetree/bindings/usb/exynos-usb.txt
>> index d967ba1..a90c973 100644
>> --- a/Documentation/devicetree/bindings/usb/exynos-usb.txt
>> +++ b/Documentation/devicetree/bindings/usb/exynos-usb.txt
>> @@ -38,6 +38,15 @@ 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 OHCI phys, they should be listed here.
>> +   One phy per port. Each port should have following entries:
>> +       - reg: port number on OHCI controller, e.g
>> +              On Exynos5250, port 0 is USB2.0 otg phy
>> +                             port 1 is HSIC phy0
>> +                             port 2 is HSIC phy1
>> +       - phys: from the *Generic PHY* bindings, specifying phy used by
>> port.
>> +       - phy-names: from the *Generic PHY* bindings, specifying name of
>> phy
>> +                    used by the port.
>
>
> I think you don't need this property for this binding, as the PHYs are being
> requested by indices (in fact only index 0 is used).

True, that phy-names property is not used, since PHYs are being
requested using indices.
We can remove this.

>
>
>>
>>   Example:
>>         usb@12120000 {
>> @@ -47,6 +56,16 @@ Example:
>>
>>                 clocks = <&clock 285>;
>>                 clock-names = "usbhost";
>> +
>> +               #address-cells = <1>;
>> +               #size-cells = <0>;
>> +               port@0 {
>> +                   reg = <0>;
>> +                   phys = <&usb2phy 1>;
>> +                   phy-names = "host";
>
>
> Ditto.
will remove this.

>
>
>> +                   status = "disabled";
>> +               };
>> +
>>         };
>>
>>   DWC3
>> diff --git a/drivers/usb/host/ohci-exynos.c
>> b/drivers/usb/host/ohci-exynos.c
>> index 05f00e3..f90bf9a 100644
>> --- a/drivers/usb/host/ohci-exynos.c
>> +++ b/drivers/usb/host/ohci-exynos.c
>> @@ -18,6 +18,7 @@
>>   #include <linux/module.h>
>>   #include <linux/of.h>
>>   #include <linux/platform_device.h>
>> +#include <linux/phy/phy.h>
>>   #include <linux/usb/phy.h>
>>   #include <linux/usb/samsung_usb_phy.h>
>>   #include <linux/usb.h>
>> @@ -33,28 +34,122 @@ static struct hc_driver __read_mostly
>> exynos_ohci_hc_driver;
>>
>>   #define to_exynos_ohci(hcd) (struct exynos_ohci_hcd
>> *)(hcd_to_ohci(hcd)->priv)
>>
>> +#define PHY_NUMBER 3
>
>
> nit: A blank line would be nice here to separate from the struct below.

Ok, will add one.

>
> By the way, doesn't the number of PHY ports depend on platform? Of course
> right now the driver supports only Exynos >= 4210 SoCs with the generic PHY
> interface, so it might be changed in further patches.

Yes, the number of PHY ports will be platform dependent feature.
In subsequent patches we can add support to count the number of PHYs,
or rather in this patch
itself, when we do -
         for_each_available_child_of_node(dev->of_node, child) {
we can keep a count of how many child nodes we found, and then
configure those many.
As such the host controller drivers will have 'host' and 'hsic' PHYs.

>
>
>>   struct exynos_ohci_hcd {
>>         struct clk *clk;
>>         struct usb_phy *phy;
>>         struct usb_otg *otg;
>> +       struct phy *phy_g[PHY_NUMBER];
>>   };
>>
>> -static void exynos_ohci_phy_enable(struct device *dev)
>> +static int exynos_ohci_get_phy(struct device *dev,
>> +                               struct exynos_ohci_hcd *exynos_ohci)
>> +{
>> +       struct device_node *child;
>> +       struct phy *phy;
>> +       int phy_number;
>> +       int ret = 0;
>> +
>> +       exynos_ohci->phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB2);
>> +       if (IS_ERR(exynos_ohci->phy)) {
>> +               ret = PTR_ERR(exynos_ohci->phy);
>> +               /* This is the case when PHY config is disabled */
>> +               if (ret == -ENXIO || ret == -ENODEV) {
>> +                       dev_dbg(dev, "Failed to get usb2 phy\n");
>> +                       exynos_ohci->phy = NULL;
>
>
> I think you should keep this an ERR_PTR() and just use IS_ERR() check
> further in the driver instead of checking for NULL.

Yea, that's also one way to check for phy, i can modify this.

>
>> +                       ret = 0;
>
>
> Do you need to set ret to 0 here? The code for getting generic PHYs will
> either leave it unchanged when there are no port nodes defined or overwrite
> it with value returned by of_property_read_u32(). In the first case, an
> error code should be returned, not zero, as the driver was unable to get any
> PHY.

The idea was to not fail exynos_ohci_get_phy() call when the PHY
configs are not even enabled.
Since this would mean, that the driver will never be able to get a PHY
in future, and there will be no point in
failing the driver probe.

In a case when the host controller dts is still on older PHY bindings,
this 'ret' will *not* be over-wriiten, since the
generic phy nodes will not be there.
And in case the host dts is moved to the new generic PHY based
bindings. then the part of this function exynos_ohci_get_phy()
related to older usb-phy, shall not execute.

This is reason why i did not really add a fall-back mechanism for getting PHY.
Since from DT either of the two bindings be supplied, and then things
here will be handles almost independently.

>
>
>> +               } else if (ret == -EPROBE_DEFER) {
>
>
> I think you could merge this case with the else clause below, as most driver
> do. Moreover, since the only thing done after the fail_phy label is
> returning the error code, you could just immediately return from here. So
> the whole block of code would end up like this:
>
>         if (IS_ERR(exynos_ohci->phy)) {
>                 ret = PTR_ERR(exynos_ohci->phy);
>                 if (ret != -ENXIO && ret != -ENODEV) {
>
>                         dev_err(dev, "no usb2 phy configured\n");
>                         return ret;
>
>                 }
>                 dev_dbg(dev, "Failed to get usb2 phy\n");
>                 exynos_ohci->phy = NULL;
>         } else {
>
>                 exynos_ohci->otg = exynos_ohci->phy->otg;
>         }

Ok, this seems a good restructuring. I shall change this.

>
>> +                       goto fail_phy;
>>
>> +               } else {
>> +                       dev_err(dev, "no usb2 phy configured\n");
>> +                       goto fail_phy;
>> +               }
>> +       } else {
>> +               exynos_ohci->otg = exynos_ohci->phy->otg;
>> +       }
>> +
>> +       /* Getting generic phy:
>
>
> CodingStyle: Multi-line comments should begin and end with a single empty
> line:
>
>         /*
>          * Getting generic phy:
>          * ...
>          */
>
> also nit: s/phy/PHY/
>

Ok, will correct this.

>
>> +        * We are keeping both types of phys as a part of transiting OHCI
>> +        * to generic phy framework, so that in absence of supporting dts
>> +        * changes the functionality doesn't break.
>> +        * Once we move the ohci dt nodes to use new generic phys,
>> +        * we can remove support for older PHY in this driver.
>
>
> Well, this is not entirely true. The problem here is not caused by existing
> DTS files, but rather a chance that there are existing devices using DTB
> files built from them. So to remove the support for old bindings, we need to
> make sure that such devices have their DTBs updated to ones built from new
> DTS.

Fair enough, thanks for explaining. :-)
I shall modify this comment.

>
>
>> +        */
>> +       for_each_available_child_of_node(dev->of_node, child) {
>> +               ret = of_property_read_u32(child, "reg", &phy_number);
>> +               if (ret) {
>> +                       dev_err(dev, "Failed to parse device tree\n");
>> +                       of_node_put(child);
>> +                       goto fail_phy;
>
>
> Why not just return ret here?
>
>> +               }
>
>
> nit: Blank line here would be nice.

ok

>
>
>> +               if (phy_number >= PHY_NUMBER) {
>> +                       dev_err(dev, "Invalid number of PHYs\n");
>> +                       of_node_put(child);
>> +                       ret = -EINVAL;
>> +                       goto fail_phy;
>
>
> What about just return -EINVAL;

Yea, just another way of doing things. ;-)
I felt 'goto' to be a bit clean than adding number of returns in
between statements.

>
>> +               }
>
>
> nit: Here too.
yea, will add a blank line.

>
>> +               phy = devm_of_phy_get(dev, child, 0);
>> +               of_node_put(child);
>> +               if (IS_ERR(phy)) {
>> +                       ret = PTR_ERR(phy);
>> +                       /* This is the case when PHY config is disabled */
>> +                       if (ret == -ENOSYS || ret == -ENODEV) {
>> +                               dev_dbg(dev, "Failed to get usb2 phy\n");
>> +                               phy = NULL;
>>
>> +                               ret = 0;
>> +                       } else if (ret == -EPROBE_DEFER) {
>> +                               goto fail_phy;
>> +                       } else {
>> +                               dev_err(dev, "no usb2 phy configured\n");
>> +                               goto fail_phy;
>> +                       }
>> +               }
>
>
> Similar comments to this block apply as for the block getting legacy USB
> PHY.

Ok, i will restructure this same as 'legacy PHY  block'

>
>
>> +               exynos_ohci->phy_g[phy_number] = phy;
>> +       }
>> +
>> +fail_phy:
>> +       return ret;
>> +}
>> +
>> +static int exynos_ohci_phy_enable(struct device *dev)
>>   {
>>         struct usb_hcd *hcd = dev_get_drvdata(dev);
>>         struct exynos_ohci_hcd *exynos_ohci = to_exynos_ohci(hcd);
>> +       int i;
>> +       int ret = 0;
>>
>> -       if (exynos_ohci->phy)
>> -               usb_phy_init(exynos_ohci->phy);
>> +       if (exynos_ohci->phy) {
>
>
> !IS_ERR() should be used to check for validity.

Ok, this with the earlier change of setting exynos_ohci->phy as
ERR_PTR(), should be good then.

>
>
>> +               ret = usb_phy_init(exynos_ohci->phy);
>> +               if (ret)
>> +                       return ret;
>
>
> IMHO a simple return usb_phy_init(...) could be used here, if we are using
> the legacy PHY interface.

Right, with legacy PHY, just a 'return usb_phy_init(...)' should do;
since those devices will not have the generic
PHYs.

>
>
>> +       }
>> +
>> +       for (i = 0; ret == 0 && i < PHY_NUMBER; i++)
>> +               if (exynos_ohci->phy_g[i])
>
>
> !IS_ERR(). Just make sure that the array is initialized with an ERR_PTR()
> with some error code, (-ENODEV) probably

Ok.

>
>
>> +                       ret = phy_power_on(exynos_ohci->phy_g[i]);
>> +       if (ret) {
>> +               for (i--; i >= 0; i--)
>> +                       if (exynos_ohci->phy_g[i])
>
>
> Ditto.
>
>
>> +                               phy_power_off(exynos_ohci->phy_g[i]);
>> +               if (exynos_ohci->phy)
>> +                       usb_phy_shutdown(exynos_ohci->phy);
>
>
> I don't think handling of legacy PHY is needed here. I don't think we can
> have both legacy and generic PHY used at the same time.

Right, we will not have both the PHYs existing at the same time.
And if we are doing a simple return usb_phy_init(...); then ofcourse
we will not need to do this.

>
>
>> +       }
>> +
>> +       return ret;
>>   }
>>
>>   static void exynos_ohci_phy_disable(struct device *dev)
>>   {
>>         struct usb_hcd *hcd = dev_get_drvdata(dev);
>>         struct exynos_ohci_hcd *exynos_ohci = to_exynos_ohci(hcd);
>> +       int i;
>>
>>         if (exynos_ohci->phy)
>>                 usb_phy_shutdown(exynos_ohci->phy);
>> +
>> +       for (i = 0; i < PHY_NUMBER; i++)
>> +               if (exynos_ohci->phy_g[i])
>
>
> !IS_ERR()

Yes.



-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
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