Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754011AbeAIKKM (ORCPT + 1 other); Tue, 9 Jan 2018 05:10:12 -0500 Received: from mail.free-electrons.com ([62.4.15.54]:48487 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753531AbeAIKJw (ORCPT ); Tue, 9 Jan 2018 05:09:52 -0500 From: Maxime Ripard To: Daniel Vetter , David Airlie , Chen-Yu Tsai , Maxime Ripard Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Thomas Petazzoni , narmstrong@baylibre.com, thomas@vitsch.nl Subject: [PATCH v3 12/13] drm/sun4i: backend: Make sure we don't have a commit pending Date: Tue, 9 Jan 2018 11:09:25 +0100 Message-Id: X-Mailer: git-send-email 2.14.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: If we try to read the backend registers while it fetches the new values, we end up with the value of some random register instead of the one we asked for. In order to prevent that, let's make sure that the very first thing we do during our atomic modesetting is to let the commit bit come to a rest. We don't have to worry about anything else since the only time we will trigger a new transaction is during the atomic_commit which comes much later. Reviewed-by: Chen-Yu Tsai Signed-off-by: Maxime Ripard --- drivers/gpu/drm/sun4i/sun4i_backend.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c index 4642f933765e..a18c86a15748 100644 --- a/drivers/gpu/drm/sun4i/sun4i_backend.c +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c @@ -297,6 +297,17 @@ static bool sun4i_backend_plane_uses_frontend(struct drm_plane_state *state) return sun4i_backend_plane_uses_scaler(state); } +static void sun4i_backend_atomic_begin(struct sunxi_engine *engine, + struct drm_crtc_state *old_state) +{ + u32 val; + + WARN_ON(regmap_read_poll_timeout(engine->regs, + SUN4I_BACKEND_REGBUFFCTL_REG, + val, !(val & SUN4I_BACKEND_REGBUFFCTL_LOADCTL), + 100, 50000)); +} + static int sun4i_backend_atomic_check(struct sunxi_engine *engine, struct drm_crtc_state *crtc_state) { @@ -478,6 +489,7 @@ static struct sun4i_frontend *sun4i_backend_find_frontend(struct sun4i_drv *drv, } static const struct sunxi_engine_ops sun4i_backend_engine_ops = { + .atomic_begin = sun4i_backend_atomic_begin, .atomic_check = sun4i_backend_atomic_check, .commit = sun4i_backend_commit, .layers_init = sun4i_layers_init, -- git-series 0.9.1