linux-kernel - Re: [PATCH] usb: dwc3: core: power on PHYs before initializing core

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Message-ID: <20180117214601.GA111796@google.com>
Date:   Wed, 17 Jan 2018 13:46:03 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     William Wu <william.wu@...k-chips.com>
Cc:     balbi@...nel.org, gregkh@...uxfoundation.org, heiko@...ech.de,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, frank.wang@...k-chips.com,
        huangtao@...k-chips.com, dianders@...gle.com, groeck@...gle.com,
        daniel.meng@...k-chips.com, John.Youn@...opsys.com,
        lin.huang@...k-chips.com
Subject: Re: [PATCH] usb: dwc3: core: power on PHYs before initializing core

On Fri, Jan 12, 2018 at 12:00:16PM +0800, William Wu wrote:
> The dwc3_core_init() gets the PHYs and initializes the PHYs with
> the usb_phy_init() and phy_init() functions before initializing
> core, and power on the PHYs after core initialization is done.
> 
> However, some platforms (e.g. Rockchip RK3399 DWC3 with Type-C
> USB3 PHY), it needs to do some special operation while power on
> the Type-C PHY before initializing DWC3 core. It's because that
> the RK3399 Type-C PHY requires to hold the DWC3 controller in
> reset state to keep the PIPE power state in P2 while configuring
> the Type-C PHY, otherwise, it may cause waiting for the PIPE ready
> timeout. In this case, if we power on the PHYs after the DWC3 core
> initialization is done, the core will be reset to uninitialized
> state after power on the PHYs.
> 
> Fix this by powering on the PHYs before initializing core. And
> because the GUID register may also be reset in this case, so we
> need to configure the GUID register after powering on the PHYs.
> 
> Signed-off-by: William Wu <william.wu@...k-chips.com>

This kinda should be part of your series:

[PATCH 0/3] Reset USB3 controller before initializing Type-C PHY on rk3399

or at least mentioned there, because the series there doesn't quite
right otherwise, no?

Anyway, I think this patch looks OK. I don't immediately see good
reasons for delaying the PHY init until later, and I do see reasons why
it could be useful earlier:

Reviewed-by: Brian Norris <briannorris@...omium.org>

> ---
>  drivers/usb/dwc3/core.c | 46 ++++++++++++++++++++++------------------------
>  1 file changed, 22 insertions(+), 24 deletions(-)