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Message-ID: <20131015141221.GM11380@radagast>
Date: Tue, 15 Oct 2013 09:12:21 -0500
From: Felipe Balbi <balbi@...com>
To: Roger Quadros <rogerq@...com>
CC: <balbi@...com>, Vivek Gautam <gautamvivek1987@...il.com>,
Kishon Vijay Abraham I <kishon@...com>,
<bcousson@...libre.com>, <tony@...mide.com>,
<rob.herring@...xeda.com>, <pawel.moll@....com>,
<mark.rutland@....com>, <linux@....linux.org.uk>,
<grant.likely@...aro.org>, <s.nawrocki@...sung.com>,
<galak@...eaurora.org>, <swarren@...dotorg.org>,
<ian.campbell@...rix.com>, <rob@...dley.net>,
<george.cherian@...com>, <gregkh@...uxfoundation.org>,
<linux-doc@...r.kernel.org>, <linux-omap@...r.kernel.org>,
<devicetree@...r.kernel.org>, <linux-usb@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] usb: dwc3: adapt dwc3 core to use Generic PHY
Framework
On Tue, Oct 15, 2013 at 05:03:50PM +0300, Roger Quadros wrote:
> On 10/15/2013 04:56 PM, Felipe Balbi wrote:
> > Hi,
> >
> > On Tue, Oct 15, 2013 at 04:48:51PM +0300, Roger Quadros wrote:
> >> On 10/15/2013 04:19 PM, Felipe Balbi wrote:
> >>> Hi,
> >>>
> >>> On Tue, Oct 15, 2013 at 03:10:42PM +0300, Roger Quadros wrote:
> >>>>>>>>> @@ -665,6 +669,9 @@ struct dwc3 {
> >>>>>>>>> struct usb_phy *usb2_phy;
> >>>>>>>>> struct usb_phy *usb3_phy;
> >>>>>>>>>
> >>>>>>>>> + struct phy *usb2_generic_phy;
> >>>>>>>>> + struct phy *usb3_generic_phy;
> >>>>>>>>> +
> >>>>>>>>> void __iomem *regs;
> >>>>>>>>> size_t regs_size;
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>>>> Do you have any suggestions on how to get only individual PHYs? like only
> >>>>>>> usb2phy or usb3phy?
> >>>>>>
> >>>>>> My earlier understanding was that both PHYs are needed only if .speed is "super-speed"
> >>>>>> and only usb2phy is needed for "high-speed". But as per Vivek's email it seems
> >>>>>> Samsung's exynos5 SoC doesn't need usb2phy for "super-speed".
> >>>>>>
> >>>>>> So to keeps things flexible, I can propose the following approach
> >>>>>> - if speed == 'high-speed' usb2phy must be present. usb3phy will be ignored if supplied.
> >>>>>> - if speed == 'super-speed' usb3phy must be present and usb2phy is optional but must be
> >>>>>> initialized if supplied.
> >>>>>> - if speed is not specified, we default to 'super-speed'.
> >>>>>>
> >>>>>> Felipe, does this address the issue you were facing with OMAP5?
> >>>>>
> >>>>> on OMAP5 we cannot skip USB3 PHY initialization. But then it becomes a
> >>>>> question of supporting a test feature (in OMAP5 case it would be cool to
> >>>>> force controller to lower speeds for testing) or coping with a broken
> >>>>> DTS.
> >>>>>
> >>>>
> >>>> I don't think we can protect ourselves from all possible broken
> >>>> configurations of DTS.
> >>>> I would vote for simplicity and maximum flexibility.
> >>>>
> >>>> So IMO we should just depend on DTS to provide the phys that are
> >>>> needed by the platform.
> >>>> In the driver we initialize whatever PHY is provided and don't
> >>>> complain if any or even all PHYs are missing.
> >>>
> >>> considering that DTS is an ABI, I really think eventually we *will* have
> >>> broken DTBs burned into ROM and we will have to find ways to work with
> >>> those too. Same thing already happens today with ACPI tables.
> >>>
> >>>> If this is not good enough then could you please suggest an
> >>>> alternative? Thanks.
> >>>
> >>> The alternative would be to mandate nop xceiv for the "missing" PHY, but
> >>> that doesn't solve anything, really, as DTS authors might still forget
> >>> about the NOP xceiv and you can argue that forcing NOP xceiv would be a
> >>> SW configuration.
> >>>
> >>> So, perhaps we go with the approach that all PHYs are optional, and
> >>> here's my original patch which makes USB3 PHY optional:
> >>>
> >>> commit 979b84f96e4b7559b596b2933ae198aba267f260
> >>> Author: Felipe Balbi <balbi@...com>
> >>> Date: Sun Jun 30 18:39:23 2013 +0300
> >>>
> >>> usb: dwc3: core: make USB3 PHY optional
> >>>
> >>> If we want a port to work at any speed lower
> >>> than Superspeed, it makes no sense to even
> >>> initialize/power up the USB3 transceiver,
> >>> provided it won't be used.
> >>>
> >>> We can use the oportunity to save some power
> >>> and leave the superspeed transceiver powered
> >>> off.
> >>>
> >>> There is at least one such case which is
> >>> Texas Instruments' AM437x which has one
> >>> of its USB3 ports without a matching USB3
> >>> PHY (that port is hardwired to work on USB2
> >>> only).
> >>>
> >>> Signed-off-by: Felipe Balbi <balbi@...com>
> >>>
> >>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> >>> index 74f9cf0..7a5ab93 100644
> >>> --- a/drivers/usb/dwc3/core.c
> >>> +++ b/drivers/usb/dwc3/core.c
> >>> @@ -387,16 +387,34 @@ static int dwc3_probe(struct platform_device *pdev)
> >>> if (node) {
> >>> dwc->maximum_speed = of_usb_get_maximum_speed(node);
> >>>
> >>> - dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 0);
> >>> - dwc->usb3_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 1);
> >>> + switch (dwc->maximum_speed) {
> >>> + case USB_SPEED_SUPER:
> >>> + dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 0);
> >>> + dwc->usb3_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 1);
> >>> + break;
> >>> + case USB_SPEED_HIGH:
> >>> + case USB_SPEED_FULL:
> >>> + case USB_SPEED_LOW:
> >>> + dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 0);
> >>> + break;
> >>> + }
> >>>
> >>> dwc->needs_fifo_resize = of_property_read_bool(node, "tx-fifo-resize");
> >>> dwc->dr_mode = of_usb_get_dr_mode(node);
> >>> } else if (pdata) {
> >>> dwc->maximum_speed = pdata->maximum_speed;
> >>>
> >>> - dwc->usb2_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB2);
> >>> - dwc->usb3_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB3);
> >>> + switch (dwc->maximum_speed) {
> >>> + case USB_SPEED_SUPER:
> >>> + dwc->usb2_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB2);
> >>> + dwc->usb3_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB3);
> >>> + break;
> >>> + case USB_SPEED_HIGH:
> >>> + case USB_SPEED_FULL:
> >>> + case USB_SPEED_LOW:
> >>> + dwc->usb2_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB2);
> >>> + break;
> >>> + }
> >>
> >> What if we try to get both PHYs irrespective of 'maximum_speed' but based
> >> on presence of phandle/pdata. That way there is some control in the adaptation code (dts/pdata)
> >> as to which PHYs needs to be initialized for that particular instance.
> >>
> >> This is because there doesn't seem to be a consensus between different designs.
> >> e.g. omap5 needs both phys for 'high-speed' whereas exynos5250 needs just the
> >> usb3 phy for 'super-speed'
> >
> > sure, can you write such a patch ? If it gets to my inbox in a couple
> > hours I guess I can still review and take it upstream on v3.13,
> > otherwise it's only on v3.14 :-(
>
> As this patch from Kishon is already touching this area, it would be best if
> he can send a v2 with this feature.
Alright, and so I'll wait a little longer.
cheers
--
balbi
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