From: khilman@baylibre•com (Kevin Hilman)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 4/7] phy: meson: add USB2 PHY support for Meson8b and GXBB
Date: Mon, 12 Sep 2016 10:32:44 -0700 [thread overview]
Message-ID: <7hpoo9qb0j.fsf@baylibre.com> (raw)
In-Reply-To: <CAFBinCDnMd0rtrvTMX-D_WNXHpVD8F=8Xn35jcK5jTUCre9ebA@mail.gmail.com> (Martin Blumenstingl's message of "Sun, 11 Sep 2016 15:44:03 +0200")
Martin Blumenstingl <martin.blumenstingl@googlemail•com> writes:
> On Fri, Sep 9, 2016 at 10:36 PM, Martin Blumenstingl
> <martin.blumenstingl@googlemail•com> wrote:
>> On Fri, Sep 9, 2016 at 5:33 PM, Kevin Hilman <khilman@baylibre•com> wrote:
>>> Martin Blumenstingl <martin.blumenstingl@googlemail•com> writes:
>>>
>>>> On Thu, Sep 8, 2016 at 10:53 PM, Ben Dooks <ben.dooks@codethink•co.uk> wrote:
>>>>> On 08/09/16 21:42, Kevin Hilman wrote:
>>>>>>
>>>>>> Ben Dooks <ben.dooks@codethink•co.uk> writes:
>>>>>>
>>>>>>> On 08/09/16 20:52, Martin Blumenstingl wrote:
>>>>>>>>
>>>>>>>> On Thu, Sep 8, 2016 at 9:35 PM, Kevin Hilman <khilman@baylibre•com>
>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>> + phy = devm_phy_create(&pdev->dev, NULL, &phy_meson_usb2_ops);
>>>>>>>>>> + if (IS_ERR(phy)) {
>>>>>>>>>> + dev_err(&pdev->dev, "failed to create PHY\n");
>>>>>>>>>> + return PTR_ERR(phy);
>>>>>>>>>> + }
>>>>>>>>>> +
>>>>>>>>>> + if (usb_reset_refcnt++ == 0) {
>>>>>>>>>> + ret = device_reset(&pdev->dev);
>>>>>>>>>> + if (ret) {
>>>>>>>>>> + dev_err(&phy->dev, "Failed to reset USB PHY\n");
>>>>>>>>>> + return ret;
>>>>>>>>>> + }
>>>>>>>>>> + }
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> The ref count + reset here looks like something that could/should be
>>>>>>>>> handled in a runtime PM callback.
>>>>>>>>
>>>>>>>> Unfortunately that doesn't work (as Jerome found out) because both
>>>>>>>> PHYs are sharing the same reset line.
>>>>>>>> So if the second PHY would call device_reset then it would also reset
>>>>>>>> the first PHY!
>>>>>>>>
>>>>>>>> There's a comment above the declaration of usb_reset_refcnt which
>>>>>>>> tries to explain this:
>>>>>>>> "The PHYs are sharing a common reset line -> we are only allowed to
>>>>>>>> reset once for all PHYs."
>>>>>>>> Maybe I should move this comment to the "if (usb_reset_refcnt++ == 0)
>>>>>>>> {" line to make it easier to see?
>>>>>>>>
>>>>>>>
>>>>>>> pm-runtime has refcounting in it. When one of the nodes turns on,
>>>>>>> the pm-runtime will call your driver to say there is a user when
>>>>>>> this first use turns up.
>>>>>>>
>>>>>>> If all the sub-phys turn off and drop their refcount then the driver
>>>>>>> is called to say there are no more users and you can go to sleep.
>>>>>>
>>>>>>
>>>>>> After a chat w/Martin on IRC, It turns out runtime PM wont help here.
>>>>>>
>>>>>> The reason is because there are physically two PHY devices[1]. Those 2
>>>>>> devices will be treated independely by runtime PM, and have separate
>>>>>> use-counting, which means doing what I proposed would cause a reset to
>>>>>> happen when either device was probed.
>>>>>>
>>>>>> So, I think it's OK as it is.
>>>>>
>>>>>
>>>>> Surely you can do pm_runtime_get/put on the phy's parent platform
>>>>> device and do it that way?
>>>> could you please be more specific with that (do you mean pdev->dev.parent)?
>>>> so we would use pm_runtime_{get_sync,put} with the parent, while we
>>>> would still define the runtime_resume in our driver.
>>>
>>> You'd also need to do get/put on the children, but yes, that's what Ben
>>> is suggesting.
>>>
>>> However, the problem with all of the solutions proposed (runtime PM ones
>>> included) is that we're forcing a board-specific design issue (2 devices
>>> sharing a reset line) into a driver that should not have any
>>> board-specific assumptions in it.
>>>
>>> For example, if this driver is used on another platform where different
>>> PHYs have different reset lines, then one of them (the unlucky one who
>>> is not probed first) will never get reset. So any form of per-device
>>> ref-counting is not a portable solution.
>> indeed, so in simple words we would need something like
>> reset_control_do_once(rstc, RESET/ASSERT/DEASSERT) which would
>> remember internally if any action has already been executed: if not it
>> does a _reset, _assert or _deassert and otherwise it does nothing.
> for now I've implemented something less hacky: I made the reset
> optional and only specified it for phy0.
That's slightly better, but could misbehave if devices are probed/loaded
in different order? But, that shouldn't be a blocker for the driver.
> During Jerome's tests the reset was not needed, while on my board it's
> required to bring both PHYs up.
> Additionally the USB PHY reference driver does not have any reset
> logic for newer SoCs (GXL), so making the reset optional doesn't sound
> that bad to me.
Agreed.
Kevin
next prev parent reply other threads:[~2016-09-12 17:32 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-04 21:31 [PATCH 0/7] usb/phy: Add Amlogic Meson8b and GXBB USB support Martin Blumenstingl
2016-09-04 21:31 ` [PATCH 1/7] clk: gxbb: expose USB clocks Martin Blumenstingl
2016-09-07 0:33 ` Stephen Boyd
2016-09-07 21:32 ` Martin Blumenstingl
2016-09-07 22:14 ` Stephen Boyd
2016-09-08 2:24 ` Kevin Hilman
2016-09-07 21:28 ` Stephen Boyd
2016-09-08 19:24 ` Kevin Hilman
2016-09-04 21:31 ` [PATCH 2/7] usb: dwc2: add support for Meson8b and GXBB SoCs Martin Blumenstingl
2016-09-07 21:04 ` John Youn
2016-09-04 21:31 ` [PATCH 3/7] Documentation: dt-bindings: Add documentation for the Meson USB2 PHYs Martin Blumenstingl
2016-09-04 21:31 ` [PATCH 4/7] phy: meson: add USB2 PHY support for Meson8b and GXBB Martin Blumenstingl
2016-09-08 19:35 ` Kevin Hilman
2016-09-08 19:40 ` Ben Dooks
2016-09-08 19:52 ` Martin Blumenstingl
2016-09-08 20:20 ` Ben Dooks
2016-09-08 20:42 ` Kevin Hilman
2016-09-08 20:53 ` Ben Dooks
2016-09-08 21:48 ` Martin Blumenstingl
2016-09-09 15:33 ` Kevin Hilman
2016-09-09 16:14 ` Martin Blumenstingl
2016-09-09 17:04 ` Kevin Hilman
2016-09-09 17:21 ` Ben Dooks
2016-09-09 20:37 ` Martin Blumenstingl
2016-09-16 8:19 ` Kishon Vijay Abraham I
2016-09-16 13:47 ` Arnd Bergmann
2016-09-18 19:56 ` Martin Blumenstingl
2016-09-19 4:59 ` Kishon Vijay Abraham I
2016-09-19 7:37 ` Arnd Bergmann
2016-09-09 20:36 ` Martin Blumenstingl
2016-09-11 13:44 ` Martin Blumenstingl
2016-09-12 17:32 ` Kevin Hilman [this message]
2016-09-13 15:28 ` Philipp Zabel
2016-09-13 18:38 ` Martin Blumenstingl
2016-09-14 0:59 ` Kevin Hilman
2016-09-14 8:36 ` Philipp Zabel
2016-09-14 8:37 ` Philipp Zabel
2016-09-14 21:09 ` Martin Blumenstingl
2016-09-14 8:37 ` Philipp Zabel
2016-09-14 21:23 ` Martin Blumenstingl
2016-09-15 10:30 ` Philipp Zabel
2016-09-04 21:31 ` [PATCH 5/7] ARM64: meson-gxbb: add USB Nodes Martin Blumenstingl
2016-09-05 0:23 ` Andreas Färber
2016-09-04 21:31 ` [PATCH 6/7] ARM64: meson-gxbb-p20x: Enable " Martin Blumenstingl
2016-09-04 21:31 ` [PATCH 7/7] ARM64: meson-gxbb-vega-s95: " Martin Blumenstingl
2016-09-11 13:41 ` [PATCH v2 0/6] usb/phy: Add Amlogic Meson8b and GXBB USB support Martin Blumenstingl
2016-09-11 13:41 ` [PATCH v2 1/6] usb: dwc2: add support for Meson8b and GXBB SoCs Martin Blumenstingl
2016-09-14 16:11 ` Kevin Hilman
2016-09-14 18:12 ` John Youn
2016-09-14 18:17 ` Kevin Hilman
2016-09-14 18:26 ` John Youn
2016-09-14 18:36 ` Kevin Hilman
2016-09-20 14:27 ` Rob Herring
2016-09-11 13:41 ` [PATCH v2 2/6] Documentation: dt-bindings: Add documentation for the Meson USB2 PHYs Martin Blumenstingl
2016-09-20 14:29 ` Rob Herring
2016-09-21 18:38 ` Kevin Hilman
2016-09-11 13:41 ` [PATCH v2 3/6] phy: meson: add USB2 PHY support for Meson8b and GXBB Martin Blumenstingl
2016-09-14 16:06 ` Kevin Hilman
2016-09-17 4:17 ` Kishon Vijay Abraham I
2016-09-19 16:42 ` Kevin Hilman
2016-09-20 5:01 ` Kishon Vijay Abraham I
2016-09-14 21:30 ` Martin Blumenstingl
2016-09-11 13:41 ` [PATCH v2 4/6] ARM64: meson-gxbb: add USB Nodes Martin Blumenstingl
2016-09-15 22:10 ` Kevin Hilman
2016-09-11 13:41 ` [PATCH v2 5/6] ARM64: meson-gxbb-p20x: Enable " Martin Blumenstingl
2016-09-14 18:05 ` Kevin Hilman
2016-09-15 22:09 ` Kevin Hilman
2016-09-11 13:41 ` [PATCH v2 6/6] ARM64: meson-gxbb-vega-s95: " Martin Blumenstingl
2016-09-15 22:10 ` Kevin Hilman
2016-10-01 12:18 ` [PATCH v3 0/3] usb/phy: Add Amlogic Meson8b and GXBB USB support Martin Blumenstingl
2016-10-01 12:18 ` [PATCH v3 1/3] Documentation: dt-bindings: update the meson-usb2-phy example Martin Blumenstingl
2016-10-09 1:28 ` Rob Herring
2016-10-01 12:18 ` [PATCH v3 2/3] Documentation: dt-bindings: rename meson-usb2-phy to meson8b-usb2-phy Martin Blumenstingl
2016-10-09 1:28 ` Rob Herring
2016-10-01 12:19 ` [PATCH v3 3/3] phy: meson: add USB2 PHY support for Meson8b and GXBB Martin Blumenstingl
2016-10-13 20:27 ` [PATCH v3 0/3] usb/phy: Add Amlogic Meson8b and GXBB USB support Martin Blumenstingl
2016-10-19 10:52 ` Kishon Vijay Abraham I
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