Re: [PATCH v2] phy: Track power-on and init counts in uclass

[Simon Glass <sjg@chromium.org>]

Hi Alper,

On Fri, 24 Dec 2021 at 06:06, Alper Nebi Yasak <alpernebiyasak@gmail.com> wrote:
>
> On boards using the RK3399 SoC, the USB OHCI and EHCI controllers share
> the same PHY device instance. While these controllers are being stopped
> they both attempt to power-off and deinitialize it, but trying to
> power-off the deinitialized PHY device results in a hang. This usually
> happens just before booting an OS, and can be explicitly triggered by
> running "usb start; usb stop" in the U-Boot shell.
>
> Implement a uclass-wide counting mechanism for PHY initialization and
> power state change requests, so that we don't power-off/deinitialize a
> PHY instance until all of its users want it done. The Allwinner A10 USB
> PHY driver does this counting in-driver, remove those parts in favour of
> this in-uclass implementation.
>
> The sandbox PHY operations test needs some changes since the uclass will
> no longer call into the drivers for actions matching its tracked state
> (e.g. powering-off a powered-off PHY). Update that test, and add a new
> one which simulates multiple users of a single PHY.
>
> The major complication here is that PHY handles aren't deduplicated per
> instance, so the obvious idea of putting the counts in the PHY handles
> don't immediately work. It seems possible to bind a child udevice per
> PHY instance to the PHY provider and deduplicate the handles in each
> child's uclass-private areas, like in the CLK framework. An alternative
> approach could be to use those bound child udevices themselves as the
> PHY handles. Instead, to avoid the architectural changes those would
> require, this patch solves things by dynamically allocating a list of
> structs (one per instance) in the provider's uclass-private area.
>
> Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
> ---
>
> Changes in v2:
> - Rename {phy_,}id_priv -> {phy_,}counts
> - Split phy_get_uclass_priv -> phy_{alloc,get}_counts
> - Allocate counts (or return error) in generic_phy_get_by_*()
> - Remove now-unnecessary null checks for counts of valid phy handles
>
> v1: https://patchwork.ozlabs.org/project/uboot/patch/20211210200124.19226-1-alpernebiyasak@gmail.com/
>
>  drivers/phy/allwinner/phy-sun4i-usb.c |   9 --
>  drivers/phy/phy-uclass.c              | 120 ++++++++++++++++++++++++++
>  test/dm/phy.c                         |  83 ++++++++++++++++--
>  3 files changed, 198 insertions(+), 14 deletions(-)

Reviewed-by: Simon Glass <sjg@chromium.org>

Should add comments for the struct

Also I wonder if a simple fixed-length array might be possible instead
of the linked list?