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Date:	Fri, 11 Jul 2014 09:10:20 +0530
From:	Vivek Gautam <gautam.vivek@...sung.com>
To:	Julius Werner <jwerner@...omium.org>
Cc:	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kishon <kishon@...com>, Kukjin Kim <kgene.kim@...sung.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Pratyush Anand <pratyush.anand@...com>
Subject: Re: [PATCH v2 2/4] usb: host: xhci-plat: Get PHYs for xhci's hcds

Hi Julius,


On Wed, Jul 9, 2014 at 11:26 PM, Julius Werner <jwerner@...omium.org> wrote:
> On Wed, Jul 9, 2014 at 3:01 AM, Vivek Gautam <gautam.vivek@...sung.com> wrote:
>> The host controller by itself may sometimes need to handle PHY
>> and/or calibrate some of the PHY settings to get full support out
>> of the PHY controller. The PHY core provides a calibration
>> funtionality now to do so.
>> Therefore, facilitate getting the two possible PHYs, viz.
>> USB 2.0 type (UTMI+) and USB 3.0 type (PIPE3), provided
>> by the parent - Synopsys's DWC3 controller
>>
>> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
>> ---
>>  drivers/usb/host/xhci-plat.c |   36 ++++++++++++++++++++++++++++++++++++
>>  1 file changed, 36 insertions(+)
>>
>> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
>> index 29d8adb..e50bd7d 100644
>> --- a/drivers/usb/host/xhci-plat.c
>> +++ b/drivers/usb/host/xhci-plat.c
>> @@ -16,6 +16,7 @@
>>  #include <linux/module.h>
>>  #include <linux/of.h>
>>  #include <linux/platform_device.h>
>> +#include <linux/phy/phy.h>
>>  #include <linux/slab.h>
>>
>>  #include "xhci.h"
>> @@ -101,6 +102,7 @@ static int xhci_plat_probe(struct platform_device *pdev)
>>         struct clk              *clk;
>>         int                     ret;
>>         int                     irq;
>> +       struct device           *parent;
>>
>>         if (usb_disabled())
>>                 return -ENODEV;
>> @@ -165,6 +167,23 @@ static int xhci_plat_probe(struct platform_device *pdev)
>>                         goto unmap_registers;
>>         }
>>
>> +       parent = pdev->dev.parent;
>> +       /*
>> +        * Get possile USB 2.0 type PHY (UTMI+) registered by xhci's parent:
>> +        * Synopsys-dwc3
>> +        */
>> +       if (of_device_is_compatible(parent->of_node, "synopsys,dwc3") ||
>> +           of_device_is_compatible(parent->of_node, "snps,dwc3")) {
>> +               hcd->gen_phy = devm_phy_get(&pdev->dev, "usb2-phy");
>> +               if (IS_ERR(hcd->gen_phy)) {
>> +                       ret = PTR_ERR(hcd->gen_phy);
>> +                       if (ret != -ENOSYS && ret != -ENODEV) {
>> +                               dev_err(&pdev->dev, "no usb2 phy configured\n");
>> +                               return ret;
>> +                       }
>> +               }
>> +       }
>
> Why does this need to check for DWC3? I think this code should be as
> generic as possible. Can't you just devm_phy_get("usb2-phy"), and keep
> going with a dev_dbg() message if it fails? If the platform has a phy
> it will find it, if not that's fine too.

Right, i was misled with the phy requisition in usb_add_hcd(), which i
thought would be
called first, and we would have been trying to overwrite the 'gen_phy'
member here. My bad!!

You are right, in this case we will not need the check for DWC3, and
we will still have the
liberty to get two different PHYs (usb2-phy and usb3-phy).

>
> Looks like Heikki's patch assigns the phy names in DWC3-specific code,
> so I'm not sure if they are supposed to be specific to that
> controller... but DWC3 is the only merged XHCI controller this applys
> to right now, so why not make that a general convention? The concept
> of having one "usb2-phy" and one "usb3-phy" is probably common across
> most xHC implementations (unless they share a single phy in which case
> they could just leave one of them unset), so it will be much easier to
> handle if they all chose the same two names for those (and we can
> avoid a big list of special cases here).

Right, i will remove these checks then, and let this be generic so that each
xHCI could get 'usb2-phy' and 'usb3-phy', if it's available.

>
>> +
>>         ret = usb_add_hcd(hcd, irq, IRQF_SHARED);
>>         if (ret)
>>                 goto disable_clk;
>> @@ -191,6 +210,23 @@ static int xhci_plat_probe(struct platform_device *pdev)
>>         if (HCC_MAX_PSA(xhci->hcc_params) >= 4)
>>                 xhci->shared_hcd->can_do_streams = 1;
>>
>> +       /*
>> +        * Get possile USB 3.0 type PHY (PIPE3) registered by xhci's parent:
>> +        * Synopsys-dwc3
>> +        */
>> +       if (of_device_is_compatible(parent->of_node, "synopsys,dwc3") ||
>> +           of_device_is_compatible(parent->of_node, "snps,dwc3")) {
>> +               xhci->shared_hcd->gen_phy = devm_phy_get(&pdev->dev,
>> +                                                        "usb3-phy");
>> +               if (IS_ERR(xhci->shared_hcd->gen_phy)) {
>> +                       ret = PTR_ERR(xhci->shared_hcd->gen_phy);
>> +                       if (ret != -ENOSYS && ret != -ENODEV) {
>> +                               dev_err(&pdev->dev, "no usb3 phy configured\n");
>> +                               return ret;
>> +                       }
>> +               }
>> +       }
>> +
>>         ret = usb_add_hcd(xhci->shared_hcd, irq, IRQF_SHARED);
>>         if (ret)
>>                 goto put_usb3_hcd;
>> --
>> 1.7.10.4
>>
> --
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-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
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