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 X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4AE2C4743C for ; Wed, 23 Jun 2021 13:59:33 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 8A2526023E for ; Wed, 23 Jun 2021 13:59:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8A2526023E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 07A196E0DA; Wed, 23 Jun 2021 13:59:33 +0000 (UTC) Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2A38D6E0DA for ; Wed, 23 Jun 2021 13:59:32 +0000 (UTC) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 3BFB08B6; Wed, 23 Jun 2021 15:59:30 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1624456770; bh=ls/eY08oJTMff7wXCIzJl5jDcaF07GxdUrqlqumyQlk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bmYlxvycnAJOUUYXnTZAiCI2wiZcvSbKYDGHrDJZj/n7UTdR3miefqbbbac14UClR iNygB7GGJuNExmPzrPtDwI9yEk7RUWZg0eWqKO+lwaX2SOqmiVKUs1bSiYJE9hZs9C GzGeOpjQkMCbwowMeW/EiSWZnG0COXA+nlnDckX0= Date: Wed, 23 Jun 2021 16:59:00 +0300 From: Laurent Pinchart To: Doug Anderson Subject: Re: [RFC PATCH 10/11] drm/bridge: ti-sn65dsi86: Support DisplayPort (non-eDP) mode Message-ID: References: <20210322030128.2283-1-laurent.pinchart+renesas@ideasonboard.com> <20210322030128.2283-11-laurent.pinchart+renesas@ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jernej Skrabec , Neil Armstrong , Jonas Karlman , Kieran Bingham , dri-devel , Stephen Boyd , linux-renesas-soc@vger.kernel.org, Andrzej Hajda Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Doug, On Wed, Mar 24, 2021 at 03:47:07PM -0700, Doug Anderson wrote: > On Sun, Mar 21, 2021 at 8:02 PM Laurent Pinchart wrote: > > > > Despite the SN65DSI86 being an eDP bridge, on some systems its output is > > routed to a DisplayPort connector. Enable DisplayPort mode when the next > > component in the display pipeline is not a panel, and disable eDP > > features in that case. > > > > Signed-off-by: Laurent Pinchart > > --- > > drivers/gpu/drm/bridge/ti-sn65dsi86.c | 32 ++++++++++++++++++++------- > > 1 file changed, 24 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c > > index e2527d597ccb..f792227142a7 100644 > > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c > > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c > > @@ -55,6 +55,7 @@ > > #define SN_LN_ASSIGN_REG 0x59 > > #define LN_ASSIGN_WIDTH 2 > > #define SN_ENH_FRAME_REG 0x5A > > +#define ASSR_CONTROL BIT(0) > > #define VSTREAM_ENABLE BIT(3) > > #define LN_POLRS_OFFSET 4 > > #define LN_POLRS_MASK 0xf0 > > @@ -86,6 +87,8 @@ > > #define SN_DATARATE_CONFIG_REG 0x94 > > #define DP_DATARATE_MASK GENMASK(7, 5) > > #define DP_DATARATE(x) ((x) << 5) > > +#define SN_TRAINING_SETTING_REG 0x95 > > +#define SCRAMBLE_DISABLE BIT(4) > > #define SN_ML_TX_MODE_REG 0x96 > > #define ML_TX_MAIN_LINK_OFF 0 > > #define ML_TX_NORMAL_MODE BIT(0) > > @@ -723,6 +726,11 @@ static int ti_sn_link_training(struct ti_sn_bridge *pdata, int dp_rate_idx, > > regmap_update_bits(pdata->regmap, SN_DATARATE_CONFIG_REG, > > DP_DATARATE_MASK, DP_DATARATE(dp_rate_idx)); > > > > + /* For DisplayPort, use the standard DP scrambler seed. */ > > + if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) > > + regmap_update_bits(pdata->regmap, SN_ENH_FRAME_REG, > > + ASSR_CONTROL, 0); > > I don't actually know anything about DP scrambler seeds. However: > > 1. From reading the docs, this field seems to be documented to be > "read only" unless: > > 1a) The "TEST2" pin is pulled high when you power on the bridge. > 1b) You set "ASSR_OVERRIDE" (page select to page 7, write to register > 0x16, page select back to page 0). > > I don't know if TEST2 is being pulled high in your hardware, but at > least I can see that 1b) isn't done. So I'm guessing that this line is > a no-op? If I had to guess from all the hoops they're making you jump > through there's some sort of errata around standard scrambling on this > bridge chip. Are you sure it works OK? Good question :-) We managed to get the SN65DSI86 to work with an external DP monitor yesterday, so it's possible (some modes don't operate correctly yet, but I assume that to be an issue with the DSI encoder). The TEST2 pin is strapped to ground on the board. According to the DisplayPort specification, eDP and DP use different scrambler seeds to prevent interoperability between an eDP source and a DP sink. I'll check what happens without this change. > 2. The docs I see claim that this field is 2 bits big. It seems like > it would be nice to honor. Yeah, it's silly because 0x11 and 0x10 are > "reserved" so it's really more like a 1-bit field, but still seems > like it would be better to set both bits, or at least add a comment > explaining why you're not matching the datasheet. Sure. > 3. Your patch doesn't seem to touch the bit of code in > ti_sn_bridge_enable() that says this: > > /** > * The SN65DSI86 only supports ASSR Display Authentication method and > * this method is enabled by default. An eDP panel must support this > * authentication method. We need to enable this method in the eDP panel > * at DisplayPort address 0x0010A prior to link training. > */ > drm_dp_dpcd_writeb(&pdata->aux, DP_EDP_CONFIGURATION_SET, > DP_ALTERNATE_SCRAMBLER_RESET_ENABLE); > > Won't that be a problem? I'll have a look. > > + > > /* enable DP PLL */ > > regmap_write(pdata->regmap, SN_PLL_ENABLE_REG, 1); > > > > @@ -734,6 +742,11 @@ static int ti_sn_link_training(struct ti_sn_bridge *pdata, int dp_rate_idx, > > goto exit; > > } > > > > + /* For DisplayPort, disable scrambling mode. */ > > + if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) > > + regmap_update_bits(pdata->regmap, SN_TRAINING_SETTING_REG, > > + SCRAMBLE_DISABLE, SCRAMBLE_DISABLE); > > I'm assuming that this is the important part of your patch? Would be > sorta nice to include the "why" in your comment. Why do you want to > disable scrambling mode for DP but not for eDP? Maybe you care about > compatibility but not EMI if you're hooking up to random DP things? I'll investigate and include proper documentation in v2 (or drop the change altogether if it's not required). -- Regards, Laurent Pinchart