From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 11E0D7765D; Wed, 24 Jan 2024 17:59:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706119146; cv=none; b=iOULFCy4PKaeMuAPpEtoKCiSjNvhATpFx+BSBm18xG3yG+A9d3M/CjyoXo+nwwsTdRZ0dyPzKQsB5rR2DRYCN4KpqzhgLNV+q4wyi2bG7/MQOCzcWlk/C262OE0YMDQ+F+A12K61VYhKzyPhPMqNvdnz0FU+VSnaztHmFEAeQfs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706119146; c=relaxed/simple; bh=Cm7BUzwChHap3mEfOgJloaWrqZWdOhIAJHyy+U2xyWo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KqXkqhCMOuygIK9k6o+ocQTQEqzBN8Ahn96+iBDuPxPBx6SG1uG7A3p2j+v9R45jU2J3g2SHSjC0pVZJEro8OWCNR/w9r71Kgd5fRXygw237LWCYmHEjo3d4A+BNbtAYG3+c01wJaQLpAEOtHO2kR/PlvSoSkqtvbL/DvPm5GhQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=keq5e3oG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="keq5e3oG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2925C433C7; Wed, 24 Jan 2024 17:59:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706119145; bh=Cm7BUzwChHap3mEfOgJloaWrqZWdOhIAJHyy+U2xyWo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=keq5e3oG7YzoqplhWADOaCbnPxZisQAEE8B8Sifw4trHPchjoYKZvIXFsxzs647Fy ysA1MC8lyGQKGf662tm7oMMRvtDhDDqS4u84Ds+Sk+l5ORJ9deHw0RkgPJLPwLMpJZ h05iQGZQWzgpiJNUZThPGNQYIgq7sjs1lWFhVPpRovXNC3PvLcb9A7p4RgUulCGrik bemz4JzwY2hLA0wCM2AL4S1NJMfuduKPMyHjsqQEN/mFMwy0n89Z64nY/LrF7rLjdF RkAcUcFtxj0gKU39Plq+/n+pv6u4k01huRkZqfgRD/BP9uBhb6MblNdozcWJQUJuC+ HJZabfG0Hk7tg== Date: Wed, 24 Jan 2024 17:59:00 +0000 From: Conor Dooley To: Frank Li Cc: ran.wang_1@nxp.com, Greg Kroah-Hartman , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Felipe Balbi , "open list:USB SUBSYSTEM" , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , open list , mark.rutland@arm.com, pku.leo@gmail.com, sergei.shtylyov@cogentembedded.com Subject: Re: [PATCH 1/2] dt-bindings: usb: dwc3: Add snps,host-vbus-glitches avoiding vbus glitch Message-ID: <20240124-video-lumpiness-178c4e317f5a@spud> References: <20240119213130.3147517-1-Frank.Li@nxp.com> <20240124-unclothed-dodgy-c78b1fffa752@spud> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="nhkkh/uTdZahtS4x" Content-Disposition: inline In-Reply-To: --nhkkh/uTdZahtS4x Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jan 24, 2024 at 12:47:14PM -0500, Frank Li wrote: > On Wed, Jan 24, 2024 at 05:36:42PM +0000, Conor Dooley wrote: > > On Fri, Jan 19, 2024 at 04:31:28PM -0500, Frank Li wrote: > > > From: Ran Wang > > >=20 > > > When DWC3 is set to host mode by programming register DWC3_GCTL, VBUS > > > (or its control signal) will turn on immediately on related Root Hub > > > ports. Then the VBUS will be de-asserted for a little while during xh= ci > > > reset (conducted by xhci driver) for a little while and back to norma= l. > > >=20 > > > This VBUS glitch might cause some USB devices emuration fail if kernel > > > boot with them connected. One SW workaround which can fix this is to > > > program all PORTSC[PP] to 0 to turn off VBUS immediately after setting > > > host mode in DWC3 driver(per signal measurement result, it will be too > > > late to do it in xhci-plat.c or xhci.c). > > >=20 > > > Signed-off-by: Ran Wang > > > Reviewed-by: Peter Chen > > > Signed-off-by: Frank Li > > > --- > > > Documentation/devicetree/bindings/usb/snps,dwc3.yaml | 7 +++++++ > > > 1 file changed, 7 insertions(+) > > >=20 > > > diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/D= ocumentation/devicetree/bindings/usb/snps,dwc3.yaml > > > index 203a1eb66691f..dbf272b76e0b5 100644 > > > --- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml > > > +++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml > > > @@ -273,6 +273,13 @@ properties: > > > with an external supply. > > > type: boolean > > > =20 > > > + snps,host-vbus-glitches: > > > + description: > > > + When set, power off all Root Hub ports immediately after > > > + setting host mode to avoid vbus (negative) glitch happen in la= ter > > > + xhci reset. And the vbus will back to 5V automatically when re= set done. nit: "will return to" > > > + type: boolean > >=20 > > Why do we want to have a property for this at all? The commit message > > seems to describe a problem that's limited to specific configurations > > and appears to be somethng the driver should do unconditionally. > >=20 > > Could you explain why this cannot be done unconditionally please? >=20 > It depends on board design, not all system vbus can be controller by root > hub port. If it is always on, it will not trigger this issue. Okay, that seems reasonable to have a property for. Can you add that info to the commit message please? On another note, I like it when the property name explains why you would add it, rather than the thing it is trying to solve. Named after the disease, rather than the symptoms, if you get me. I tried to come up with a name here, but could not really suggest something good. If you can think of something, that'd be good, but don't stress it. Thanks, Conor. --nhkkh/uTdZahtS4x Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZbFP5AAKCRB4tDGHoIJi 0jMAAQCp/21Q5979/sF3RN5s/2EsZasO9EBk6OMq7hWHKqQ6bQEAonMgZ+jJ1CwA FychGYPa48OqMYsKeXJjFbuS92nlmQM= =2AIU -----END PGP SIGNATURE----- --nhkkh/uTdZahtS4x--