From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 64C0B1EB9F9 for ; Mon, 21 Oct 2024 17:07:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729530480; cv=none; b=G+T4rcKGTjLoP/rCTTJZxHsruBvjN8Od3V/C/0LtU3bG6C5ned5/c3fWKDmzftY1vw4i2t/hL9oUkDuF1uZbDbpEKb8FBEXwOHdLQyo8k32GGNCbocgVw+Q922NYONGip0sXWB7hQz8QvR4ki1NAlXKgmpOmssd163mWbN6wui0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729530480; c=relaxed/simple; bh=9HwBB6DUdlSqXu+QzXrHwnDX73SBMuj81nw+I6vhaeU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ekCUsgwzO0gZ3kVBMSAcMR2p3kDFEFZ+gj604mxiIUmWrDrpOfrDCf7LY5Vls/I6FTCSVg8Qc3xOsFTwOTwWM3prnL6tUz0tqtFpvT+oqkr7VYlxTqXEMlhWDFdkriWEMAViC5saZ/MUsXGX53S6W1308TRq8x/cDlmK10lRJrg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=jVl6/xdX; arc=none smtp.client-ip=91.218.175.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="jVl6/xdX" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1729530475; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SrQYJCnutF/B0aizIHStBs0qq9hGntt8rX3SGM0rkm4=; b=jVl6/xdXgjM0teCdVytFPKO98U3Twrb2C4GfaL2e/DYJIrQK1G9uPDRo83IlzfMtKKRNeB CX8ClxRa7Ao5d1abXKBnwszUs0uN5EGzZs/W1On5SjnRHKHFKhjNfisJ85ijDcjJc3CbI+ DmL6M/3jgIleui/Ge8URFzoYiwMrZGE= Date: Mon, 21 Oct 2024 22:37:44 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v5 13/13] drm/bridge: cdns-dsi: Use pre_enable/post_disable to enable/disable To: Dmitry Baryshkov Cc: Tomi Valkeinen , Laurent Pinchart , Andrzej Hajda , Neil Armstrong , Robert Foss , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Dominik Haller , Sam Ravnborg , Kieran Bingham , Nishanth Menon , Vignesh Raghavendra , Devarsh Thakkar , Praneeth Bajjuri , Udit Kumar , Jayesh Choudhary , DRI Development List , Linux Kernel List References: <20241019195411.266860-1-aradhya.bhatia@linux.dev> <20241019200530.270738-1-aradhya.bhatia@linux.dev> <20241019200530.270738-6-aradhya.bhatia@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Aradhya Bhatia In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Hi Dmitry, Thank you for reviewing the patches! On 10/20/24 17:27, Dmitry Baryshkov wrote: > On Sun, Oct 20, 2024 at 01:35:30AM +0530, Aradhya Bhatia wrote: >> From: Aradhya Bhatia >> >> The cdns-dsi controller requires that it be turned on completely before >> the input DPI's source has begun streaming[0]. Not having that, allows >> for a small window before cdns-dsi enable and after cdns-dsi disable >> where the previous entity (in this case tidss's videoport) to continue >> streaming DPI video signals. This small window where cdns-dsi is >> disabled but is still receiving signals causes the input FIFO of >> cdns-dsi to get corrupted. This causes the colors to shift on the output >> display. The colors can either shift by one color component (R->G, G->B, >> B->R), or by two color components (R->B, G->R, B->G). >> >> Since tidss's videoport starts streaming via crtc enable hooks, we need >> cdns-dsi to be up and running before that. Now that the bridges are >> pre_enabled before crtc is enabled, and post_disabled after crtc is >> disabled, use the pre_enable and post_disable hooks to get cdns-dsi >> ready and running before the tidss videoport to get pass the color shift >> issues. >> > > Not being an expert in the TI DSS driver, would it be more proper to > handle that in the TI driver instead? I mean, sending out DPI signals > isn't a part of the CRTC setup, it's a job of the encoder. I haven't done a feasibility analysis of moving the CRTC bits of TIDSS into the encoder, but even if it were possible, it wouldn't solve the issue. The bridge_enable() sequence gets called _after_ the encoder has been enabled - causing the TIDSS's DPI (enabled from encoder) to still be up and running before the DSI has had a chance to be ready. Regards Aradhya > >> [0]: See section 12.6.5.7.3 "Start-up Procedure" in J721E SoC TRM >> TRM Link: http://www.ti.com/lit/pdf/spruil1 >> >> Reviewed-by: Tomi Valkeinen >> Signed-off-by: Aradhya Bhatia >> Signed-off-by: Aradhya Bhatia >> --- >> .../gpu/drm/bridge/cadence/cdns-dsi-core.c | 62 ++++++++++--------- >> 1 file changed, 34 insertions(+), 28 deletions(-) >> >> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c >> index 79d8c2264c14..dfeb53841ebc 100644 >> --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c >> +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c >> @@ -658,13 +658,28 @@ cdns_dsi_bridge_mode_valid(struct drm_bridge *bridge, >> return MODE_OK; >> } >> >> -static void cdns_dsi_bridge_atomic_disable(struct drm_bridge *bridge, >> - struct drm_bridge_state *old_bridge_state) >> +static void cdns_dsi_bridge_atomic_post_disable(struct drm_bridge *bridge, >> + struct drm_bridge_state *old_bridge_state) >> { >> struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge); >> struct cdns_dsi *dsi = input_to_dsi(input); >> u32 val; >> >> + /* >> + * The cdns-dsi controller needs to be disabled after it's DPI source >> + * has stopped streaming. If this is not followed, there is a brief >> + * window before DPI source is disabled and after cdns-dsi controller >> + * has been disabled where the DPI stream is still on, but the cdns-dsi >> + * controller is not ready anymore to accept the incoming signals. This >> + * is one of the reasons why a shift in pixel colors is observed on >> + * displays that have cdns-dsi as one of the bridges. >> + * >> + * To mitigate this, disable this bridge from the bridge post_disable() >> + * hook, instead of the bridge _disable() hook. The bridge post_disable() >> + * hook gets called after the CRTC disable, where often many DPI sources >> + * disable their streams. >> + */ >> + >> val = readl(dsi->regs + MCTL_MAIN_DATA_CTL); >> val &= ~(IF_VID_SELECT_MASK | IF_VID_MODE | VID_EN | HOST_EOT_GEN | >> DISP_EOT_GEN); >> @@ -683,15 +698,6 @@ static void cdns_dsi_bridge_atomic_disable(struct drm_bridge *bridge, >> pm_runtime_put(dsi->base.dev); >> } >> >> -static void cdns_dsi_bridge_atomic_post_disable(struct drm_bridge *bridge, >> - struct drm_bridge_state *old_bridge_state) >> -{ >> - struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge); >> - struct cdns_dsi *dsi = input_to_dsi(input); >> - >> - pm_runtime_put(dsi->base.dev); >> -} >> - >> static void cdns_dsi_hs_init(struct cdns_dsi *dsi) >> { >> struct cdns_dsi_output *output = &dsi->output; >> @@ -760,8 +766,8 @@ static void cdns_dsi_init_link(struct cdns_dsi *dsi) >> dsi->link_initialized = true; >> } >> >> -static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge, >> - struct drm_bridge_state *old_bridge_state) >> +static void cdns_dsi_bridge_atomic_pre_enable(struct drm_bridge *bridge, >> + struct drm_bridge_state *old_bridge_state) >> { >> struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge); >> struct cdns_dsi *dsi = input_to_dsi(input); >> @@ -776,6 +782,21 @@ static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge, >> if (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0)) >> return; >> >> + /* >> + * The cdns-dsi controller needs to be enabled before it's DPI source >> + * has begun streaming. If this is not followed, there is a brief window >> + * after DPI source enable and before cdns-dsi controller enable where >> + * the DPI stream is on, but the cdns-dsi controller is not ready to >> + * accept the incoming signals. This is one of the reasons why a shift >> + * in pixel colors is observed on displays that have cdns-dsi as one of >> + * the bridges. >> + * >> + * To mitigate this, enable this bridge from the bridge pre_enable() >> + * hook, instead of the bridge _enable() hook. The bridge pre_enable() >> + * hook gets called before the CRTC enable, where often many DPI sources >> + * enable their streams. >> + */ >> + >> if (dsi->platform_ops && dsi->platform_ops->enable) >> dsi->platform_ops->enable(dsi); >> >> @@ -912,19 +933,6 @@ static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge, >> writel(tmp, dsi->regs + MCTL_MAIN_EN); >> } >> >> -static void cdns_dsi_bridge_atomic_pre_enable(struct drm_bridge *bridge, >> - struct drm_bridge_state *old_bridge_state) >> -{ >> - struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge); >> - struct cdns_dsi *dsi = input_to_dsi(input); >> - >> - if (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0)) >> - return; >> - >> - cdns_dsi_init_link(dsi); >> - cdns_dsi_hs_init(dsi); >> -} >> - >> static u32 *cdns_dsi_bridge_get_input_bus_fmts(struct drm_bridge *bridge, >> struct drm_bridge_state *bridge_state, >> struct drm_crtc_state *crtc_state, >> @@ -968,9 +976,7 @@ static int cdns_dsi_bridge_atomic_check(struct drm_bridge *bridge, >> static const struct drm_bridge_funcs cdns_dsi_bridge_funcs = { >> .attach = cdns_dsi_bridge_attach, >> .mode_valid = cdns_dsi_bridge_mode_valid, >> - .atomic_disable = cdns_dsi_bridge_atomic_disable, >> .atomic_pre_enable = cdns_dsi_bridge_atomic_pre_enable, >> - .atomic_enable = cdns_dsi_bridge_atomic_enable, >> .atomic_post_disable = cdns_dsi_bridge_atomic_post_disable, >> .atomic_check = cdns_dsi_bridge_atomic_check, >> .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state, >> -- >> 2.34.1 >> >