linux-kernel - Re: [PATCH v3 6/6] phy: exynos5-usbdrd: support Exynos USBDRD 3.1 combo phy (HS & SS)

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Message-ID: <CADrjBPrg6_3FhD=2W8X=yaSrTMbmcfjRo3HVo1LyHVcUM8P=0g@mail.gmail.com>
Date: Mon, 24 Jun 2024 12:33:09 +0100
From: Peter Griffin <peter.griffin@...aro.org>
To: André Draszik <andre.draszik@...aro.org>
Cc: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, Sylwester Nawrocki <s.nawrocki@...sung.com>, 
	Alim Akhtar <alim.akhtar@...sung.com>, Sam Protsenko <semen.protsenko@...aro.org>, 
	Krzysztof Kozlowski <krzk@...nel.org>, Tudor Ambarus <tudor.ambarus@...aro.org>, 
	Will McVicker <willmcvicker@...gle.com>, Roy Luo <royluo@...gle.com>, kernel-team@...roid.com, 
	linux-phy@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v3 6/6] phy: exynos5-usbdrd: support Exynos USBDRD 3.1
 combo phy (HS & SS)

Hi André,

On Mon, 17 Jun 2024 at 17:45, André Draszik <andre.draszik@...aro.org> wrote:
>
> Add support for the Exynos USB 3.1 DRD combo phy, as found in Exynos 9
> SoCs like Google GS101. It supports USB SS, HS and DisplayPort.
>
> In terms of UTMI+, this is very similar to the existing Exynos850
> support in this driver. The difference is that this combo phy supports
> both UTMI+ (HS) and PIPE3 (SS). It also supports DP alt mode.
>
> The number of ports for UTMI+ and PIPE3 can be determined using the
> LINKPORT register (which also exists on Exynos E850).
>
> For SuperSpeed (SS) a new SS phy is in use and its PIPE3 interface is
> new compared to Exynos E850, and also very different from the existing
> support for older Exynos SoCs in this driver.
>
> The SS phy needs a bit more configuration work and register tuning for
> signal quality to work reliably, presumably due to the higher
> frequency, e.g. to account for different board layouts. Additionally,
> power needs to be enabled before writing to the SS phy registers.
>
> This commit adds the necessary changes for USB HS and SS to work.
> DisplayPort is out of scope in this commit.
>
> Notes:
> * For the register tuning, exynos5_usbdrd_apply_phy_tunes() has been
>   added with the appropriate data structures to support tuning at
>   various stages during initialisation. Since these are hardware
>   specific, the platform data is supposed to be populated accordingly.
>   The implementation is loosely modelled after the Samsung UFS PHY
>   driver.
>
>   There is one tuning state for UTMI+, PTS_UTMI_POSTINIT, to execute
>   after init and generally intended for HS signal tuning, as done in
>   this commit.
>
>   PTS_PIPE3_PREINIT PTS_PIPE3_INIT PTS_PIPE3_POSTINIT
>   PTS_PIPE3_POSTLOCK are tuning states for PIPE3. In the downstream
>   driver, preinit differs by Exynos SoC, and postinit and postlock
>   are different per board. The latter haven't been implemented for
>   gs101 here, because downstream doesn't use them on gs101 either.
>
> * Signal lock acquisition for SS depends on the orientation of the
>   USB-C plug. Since there currently is no infrastructure to chain
>   connector events to both the USB DWC3 driver and this phy driver, a
>   work-around has been added in
>   exynos5_usbdrd_usbdp_g2_v4_pma_check_cdr_lock() to check both
>   registers if it failed in one of the orientations.
>
> * Equally, we can only establish SS speed in one of the connector
>   orientations due to programming differences when selecting the lane
>   mux in exynos5_usbdrd_usbdp_g2_v4_pma_lane_mux_sel(), which really
>   needs to be dynamic, based on the orientation of the connector.
>
> * As is, we can establish a HS link using any cable, and an SS link in
>   one orientation of the plug, falling back to HS if the orientation is
>   reversed to the expectation.
>
> Signed-off-by: André Draszik <andre.draszik@...aro.org>
>
> ---

Reviewed-by:  Peter Griffin <peter.griffin@...aro.org>
and
Tested-by: Peter Griffin <peter.griffin@...aro.org>

Tested using my Pixel 6 pro device. USB comes up and it is possible to
use adb from the host computer to the phone.

regards,

Peter

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