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 8D2C2C433F5 for ; Thu, 7 Oct 2021 12:15:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 743916125F for ; Thu, 7 Oct 2021 12:15:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241249AbhJGMRA (ORCPT ); Thu, 7 Oct 2021 08:17:00 -0400 Received: from fllv0016.ext.ti.com ([198.47.19.142]:48178 "EHLO fllv0016.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241135AbhJGMQ6 (ORCPT ); Thu, 7 Oct 2021 08:16:58 -0400 Received: from lelv0266.itg.ti.com ([10.180.67.225]) by fllv0016.ext.ti.com (8.15.2/8.15.2) with ESMTP id 197CEew5110477; Thu, 7 Oct 2021 07:14:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1633608880; bh=j6adkrGlMOpYlmjotVznItdFpUqevVwAnoGcm4wqQig=; h=Date:From:To:CC:Subject:References:In-Reply-To; b=DclmbGZVt7L9NxqWwXuV4C3/T+BbXENXCwuBUsExLT1jZKjbrjkza4Gu/xeY3wWhQ O3w4Xz17VCyDqkPSC3NQ/45snQXNSl3FiJNY54z9IDS5OKMAwpkostllmAfLtDzDn2 Cw+bN39D1ywxTjXU6FQXnl5zYpJJiVJjamEP0Gu4= Received: from DLEE109.ent.ti.com (dlee109.ent.ti.com [157.170.170.41]) by lelv0266.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 197CEelh108154 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 7 Oct 2021 07:14:40 -0500 Received: from DLEE106.ent.ti.com (157.170.170.36) by DLEE109.ent.ti.com (157.170.170.41) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.14; Thu, 7 Oct 2021 07:14:40 -0500 Received: from lelv0327.itg.ti.com (10.180.67.183) by DLEE106.ent.ti.com (157.170.170.36) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.14 via Frontend Transport; Thu, 7 Oct 2021 07:14:40 -0500 Received: from localhost (ileax41-snat.itg.ti.com [10.172.224.153]) by lelv0327.itg.ti.com (8.15.2/8.15.2) with ESMTP id 197CEdxL100865; Thu, 7 Oct 2021 07:14:40 -0500 Date: Thu, 7 Oct 2021 17:44:38 +0530 From: Pratyush Yadav To: Laurent Pinchart CC: Vinod Koul , Paul Kocialkowski , Vignesh Raghavendra , Tomi Valkeinen , Nikhil Devshatwar , Chunfeng Yun , Kishon Vijay Abraham I , Rob Herring , , Subject: Re: [PATCH v5 2/6] phy: cdns-dphy: Add Rx support Message-ID: <20211007121436.jkck2cue5zd3rys4@ti.com> References: <20210902185543.18875-1-p.yadav@ti.com> <20210902185543.18875-3-p.yadav@ti.com> <20210917172809.rjtf7ww7vjcfvey5@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20171215 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/10/21 03:10AM, Laurent Pinchart wrote: > Hi Vinod, > > 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 CSI-2 > > > > > protocol. Add support for Rx mode. The programming sequence differs from > > > > > the Tx mode so it is added as a separate set of hooks to isolate the two > > > > > paths. The mode in which the DPHY has to be used is selected based on > > > > > the compatible. > > > > > > > > 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. > > > > > > > > I see that you've been using a dedicated compatible, but I'm not 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 how the hardware > > > > is used specifically. I guess the distinction between rx/tx falls under > > > > the latter rather than the former. > > > > > > I am not sure if that is the case. For example, we use "ti,am654-ospi" > > > for Cadence Quadspi controller. The default compatible, "cdns,qspi-nor", > > > only supports Quad SPI (4 lines). The "ti,am654-ospi" compatible also > > > supports Octal SPI (8 lines). > > > > Those are hardware defaults right? > > > > > In addition, I feel like the Rx DPHY is almost a different type of > > > device from a Tx DPHY. The programming sequence is completely different, > > > > Is that due to direction or something else..? > > > > > the clocks required are different, etc. So I think using a different > > > compatible for Rx mode makes sense. > > > > Is the underlaying IP not capable of both TX and RX and in the specific > > situations you are using it as TX and RX. > > > > I am okay that default being TX but you can use Paul's approach of > > direction with this to make it better proposal > > > 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 PHY. > This can only be done with two different compatible strings, which I > think would be a better approach. FWIW, I think having different drivers would certainly make things easier to maintain. > > 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 backward > compatibility, making things cleaner going forward. > > -- > Regards, > > Laurent Pinchart -- Regards, Pratyush Yadav Texas Instruments Inc.