From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39929C433F5 for ; Fri, 8 Oct 2021 12:56:04 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0301E61037 for ; Fri, 8 Oct 2021 12:56:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0301E61037 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: List-Subscribe:List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: In-Reply-To:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Reply-To:Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date :Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=9C2Ru1WV/AXf2WZ0/6rPSG8dkjLLeGKLQ+9004tV8Aw=; b=rBECZMbd3mtC2CkQYvK9Xdwbaj 9gm3xJwv0ra3AtN1rTqhU7oPBDuZSTB3WAoM9eDfXCIjPO77k+nLE3sSFB1DR0oI9/icKnWC6ykN4 Bj05DrWVB8bGHoPpLdP1HmfF1o3LeiGIDAtAjs+oIoq7ceIpY1HJtiEfYYN/gPEzhx2PZ9Mn6tDBm Pp24BUiDR0EOAw5pH/oDADpzPpvN5fSMsMhdMXzxh9Ek9/OgpHBC0zb4JEyz+C637QnfSWm7fjpSt RuxK3EzTStTsZSqwOt2oF0mBNUDY4hKEY1c30VhhxIvzpeHop0+Hv0QOhN9tPWzYKPV29ABFBW4T5 +32l/z5g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mYpPv-002pHM-It; Fri, 08 Oct 2021 12:56:03 +0000 Received: from relay12.mail.gandi.net ([217.70.178.232]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mYpPs-002pG8-Fm for linux-phy@lists.infradead.org; Fri, 08 Oct 2021 12:56:02 +0000 Received: (Authenticated sender: paul.kocialkowski@bootlin.com) by relay12.mail.gandi.net (Postfix) with ESMTPSA id 11D2D20000F; Fri, 8 Oct 2021 12:55:54 +0000 (UTC) Date: Fri, 8 Oct 2021 14:55:54 +0200 From: Paul Kocialkowski To: Laurent Pinchart Cc: Pratyush Yadav , Vinod Koul , Vignesh Raghavendra , Tomi Valkeinen , Nikhil Devshatwar , Chunfeng Yun , Kishon Vijay Abraham I , Rob Herring , linux-kernel@vger.kernel.org, linux-phy@lists.infradead.org Subject: Re: [PATCH v5 2/6] phy: cdns-dphy: Add Rx support Message-ID: References: <20210902185543.18875-1-p.yadav@ti.com> <20210902185543.18875-3-p.yadav@ti.com> <20210917172809.rjtf7ww7vjcfvey5@ti.com> <20211007121436.jkck2cue5zd3rys4@ti.com> MIME-Version: 1.0 In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211008_055600_847540_107E7D15 X-CRM114-Status: GOOD ( 39.31 ) X-BeenThere: linux-phy@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux Phy Mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============5051331095793162439==" Sender: "linux-phy" Errors-To: linux-phy-bounces+linux-phy=archiver.kernel.org@lists.infradead.org --===============5051331095793162439== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="L5dYWIzivIAnCCEH" Content-Disposition: inline --L5dYWIzivIAnCCEH Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, On Fri 08 Oct 21, 13:27, Laurent Pinchart wrote: > Hi Pratyush, >=20 > On Thu, Oct 07, 2021 at 05:44:38PM +0530, Pratyush Yadav wrote: > > On 07/10/21 03:10AM, Laurent Pinchart wrote: > > > On Fri, Oct 01, 2021 at 11:53:16AM +0530, Vinod Koul wrote: > > > > On 17-09-21, 22:58, Pratyush Yadav wrote: > > > > > On 16/09/21 12:22PM, Paul Kocialkowski wrote: > > > > > > On Fri 03 Sep 21, 00:25, Pratyush Yadav wrote: > > > > > > > The Cadence DPHY can be used to receive image data over the C= SI-2 > > > > > > > protocol. Add support for Rx mode. The programming sequence d= iffers from > > > > > > > the Tx mode so it is added as a separate set of hooks to isol= ate the two > > > > > > > paths. The mode in which the DPHY has to be used is selected = based on > > > > > > > the compatible. > > > > > >=20 > > > > > > I just realized that I didn't follow-up on a previous revision = on the debate > > > > > > about using the phy sub-mode to distinguish between rx/tx. > > > > > >=20 > > > > > > I see that you've been using a dedicated compatible, but I'm no= t sure this is a > > > > > > good fit either. My understanding is that the compatible should= describe a group > > > > > > of register-compatible revisions of a hardware component, not h= ow the hardware > > > > > > is used specifically. I guess the distinction between rx/tx fal= ls under > > > > > > the latter rather than the former. > > > > >=20 > > > > > I am not sure if that is the case. For example, we use "ti,am654-= ospi"=20 > > > > > for Cadence Quadspi controller. The default compatible, "cdns,qsp= i-nor",=20 > > > > > only supports Quad SPI (4 lines). The "ti,am654-ospi" compatible = also=20 > > > > > supports Octal SPI (8 lines). > > > >=20 > > > > Those are hardware defaults right? > > > >=20 > > > > > In addition, I feel like the Rx DPHY is almost a different type o= f=20 > > > > > device from a Tx DPHY. The programming sequence is completely dif= ferent,=20 > > > >=20 > > > > Is that due to direction or something else..? > > > >=20 > > > > > the clocks required are different, etc. So I think using a differ= ent=20 > > > > > compatible for Rx mode makes sense. > > > >=20 > > > > Is the underlaying IP not capable of both TX and RX and in the spec= ific > > > > situations you are using it as TX and RX. > > > >=20 > > > > I am okay that default being TX but you can use Paul's approach of > > > > direction with this to make it better proposal > > >=20 > > >=20 > > > Given that the RX and TX implementations are very different (it's not= a > > > matter of selecting a mode at runtime), I'm actually tempted to > > > recommend having two drivers, one for the RX PHY and one for the TX P= HY. > > > This can only be done with two different compatible strings, which I > > > think would be a better approach. > >=20 > > FWIW, I think having different drivers would certainly make things=20 > > easier to maintain. >=20 > I'm sorry for not having recommended this in the first place. >=20 > Any objection from anyone against going in this direction ? So apparently there is not a single register that is shared between rx and = tx and clocks are not the same either so it feels to me like a separate driver would be legit. This looks like two distinct IPs sharing the same base addr= ess. Cheers, Paul > > > It's unfortunate that the original compatible string didn't contain > > > "tx". We could rename it and keep the old one in the driver for backw= ard > > > compatibility, making things cleaner going forward. >=20 > --=20 > Regards, >=20 > Laurent Pinchart --=20 Paul Kocialkowski, Bootlin Embedded Linux and kernel engineering https://bootlin.com --L5dYWIzivIAnCCEH Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEJZpWjZeIetVBefti3cLmz3+fv9EFAmFgP9oACgkQ3cLmz3+f v9Hxvwf/e/A29WlDAhrBrskZq6ow7NWWzWAoCdjdGQl/QDZmIe7f2+93Q97rjSLn eiXMvHxgnuvkm4KWlGM7MBEczcwbSfnZKyu48UWYsdGwfkNAvLJEka522u7nhsxY j68hda1nI6BpV7tmX4zsQH/kySF/z1Z787q/CoYl7Yq/dYxtNW8L0EDval4kbYQI vHu4CXsmFw0ToPPJd0d4wBrD8WEU8wQX6CkNhDIw92RCzMMJu7jy9FRD5/ekF93P Bty3NYcL3a9jcNoX82BeFcBbRE+xyJxeCHR8KpBAmgTaVefI3E6aoPQL1L55bN1v SuwC4/l8Bq3f03IyIv222HfPQ6rURw== =ceu9 -----END PGP SIGNATURE----- --L5dYWIzivIAnCCEH-- --===============5051331095793162439== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline -- linux-phy mailing list linux-phy@lists.infradead.org https://lists.infradead.org/mailman/listinfo/linux-phy --===============5051331095793162439==--