From patchwork Thu Nov 21 17:41:10 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miquel Raynal X-Patchwork-Id: 13882221 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 4E55FD743CA for ; Thu, 21 Nov 2024 17:41:41 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id BE10110EA0B; Thu, 21 Nov 2024 17:41:40 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=bootlin.com header.i=@bootlin.com header.b="XPJhU6Aw"; dkim-atps=neutral Received: from relay7-d.mail.gandi.net (relay7-d.mail.gandi.net [217.70.183.200]) by gabe.freedesktop.org (Postfix) with ESMTPS id 79A4F10EA08 for ; Thu, 21 Nov 2024 17:41:38 +0000 (UTC) Received: by mail.gandi.net (Postfix) with ESMTPSA id CD1472000A; Thu, 21 Nov 2024 17:41:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1732210896; 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; bh=rt80qnAyyepZvbd8DfB3ShuvRFOqvgROOwcu9fM6x3U=; b=XPJhU6AwXFGRUUnfGQvejV+oHxkMvweUkwv9ULqvHbQa8KI16HGZgTZzN7fv0AWbOGlv9k Ykr621Z3EWSQFd0/Eh4GQ5JaBq19W19D1tx0V82mCLr56bacduLtP9ITRqEX3GjJvSvt9V uixNsJpbWe4tnkysNvTuVA+/5DnMevlnv6uLbVS+q4olykwKN8OSRYr5av9Ycaaytja792 vvAB1aZOjvs8cZtuR+kon8EIZ89Mk6DHMm3EEXEKzpHJjptxGjMGNM2FVEnDLEVi4ljdD8 zb6YH3vlOoQTG6XstKJeBVuEHA85FLbEQoTmTtKrLn9gRCEAo4310ZykbKN5qQ== From: Miquel Raynal Subject: [PATCH 0/5] clk: Fix simple video pipelines on i.MX8 Date: Thu, 21 Nov 2024 18:41:10 +0100 Message-Id: <20241121-ge-ian-debug-imx8-clk-tree-v1-0-0f1b722588fe@bootlin.com> MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIALZwP2cC/x3MTQ5AMBBA4avIrE1i6ifiKmJROpigpEUk4u7K8 nuLd4NnJ+yhim5wfIqX1QZQHEE3ajswigkGlaiMSBF+RVs03B4DynKV2M0T7o4ZW5OqXOuyKHq CMNgc93L987p5nhenn/rUbAAAAA== X-Change-ID: 20241121-ge-ian-debug-imx8-clk-tree-bd325aa866f1 To: Abel Vesa , Peng Fan , Michael Turquette , Stephen Boyd , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Ying Liu , Marek Vasut Cc: Laurent Pinchart , linux-clk@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Abel Vesa , Herve Codina , Luca Ceresoli , Thomas Petazzoni , Ian Ray , Miquel Raynal , stable@vger.kernel.org X-Mailer: b4 0.15-dev X-GND-Sasl: miquel.raynal@bootlin.com 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Recent changes in the clock tree have set CLK_SET_RATE_PARENT to the two LCDIF pixel clocks. The idea is, instead of using assigned-clock properties to set upstream PLL rates to high frequencies and hoping that a single divisor (namely media_disp[12]_pix) will be close enough in most cases, we should tell the clock core to use the PLL to properly derive an accurate pixel clock rate in the first place. Here is the situation. [Before ff06ea04e4cf ("clk: imx: clk-imx8mp: Allow media_disp pixel clock reconfigure parent rate")] Before setting CLK_SET_RATE_PARENT to the media_disp[12]_pix clocks, the sequence of events was: - PLL is assigned to a high rate, - media_disp[12]_pix is set to approximately freq A by using a single divisor, - media_ldb is set to approximately freq 7*A by using another single divisor. => The display was working, but the pixel clock was inaccurate. [After ff06ea04e4cf ("clk: imx: clk-imx8mp: Allow media_disp pixel clock reconfigure parent rate")] After setting CLK_SET_RATE_PARENT to the media_disp[12]_pix clocks, the sequence of events became: - media_disp[12]_pix is set to freq A by using a divisor of 1 and setting video_pll1 to freq A. - media_ldb is trying to compute its divisor to set freq 7*A, but the upstream PLL is to low, it does not recompute it, so it ends up setting a divisor of 1 and being at freq A instead of 7*A. => The display is sadly no longer working [After applying PATCH "clk: imx: clk-imx8mp: Allow LDB serializer clock reconfigure parent rate"] This is a commit from Marek, which is, I believe going in the right direction, so I am including it. Just with this change, the situation is slightly different, but the result is the same: - media_disp[12]_pix is set to freq A by using a divisor of 1 and setting video_pll1 to freq A. - media_ldb is set to 7*A by using a divisor of 1 and setting video_pll1 to freq 7*A. /!\ This as the side effect of changing media_disp[12]_pix from freq A to freq 7*A. => The display is still not working [After applying this series] The goal of the following patches is to prevent clock subtree walks to "just recalculate" the pixel clocks, ignoring the fact that they should no longer change. They should adapt their divisors to the new upstream rates instead. As a result, the display pipeline is working again. Note: if more than one display is connected, we need the LDB driver to act accordingly, thus the LDB driver must be adapted. Also, if accurate pixel clocks are not possible with two different displays, we will still need (at least for now) to make sure one of them is reparented to another PLL, like the audio PLL (but audio PLL are of a different kind, and are slightly less accurate). So this series aims at fixing the i.MX8MP display pipeline for simple setups. Said otherwise, returning to the same level of support as before, but with (hopefully) more accurate frequencies. I believe this approach manages to fix both Marek situation and all people using a straightforward LCD based setup. For more complex setups, we need more smartness from DRM and clk, but this is gonna take a bit of time. --- Marek Vasut (1): clk: imx: clk-imx8mp: Allow LDB serializer clock reconfigure parent rate Miquel Raynal (4): clk: Add a helper to determine a clock rate clk: Split clk_calc_subtree() clk: Add flag to prevent frequency changes when walking subtrees clk: imx: imx8mp: Prevent media clocks to be incompatibly changed drivers/clk/clk.c | 39 ++++++++++++++++++++++++++++++++------- drivers/clk/imx/clk-imx8mp.c | 6 +++--- include/linux/clk-provider.h | 2 ++ 3 files changed, 37 insertions(+), 10 deletions(-) --- base-commit: 62facaf164585923d081eedcb6871f4ff3c2e953 change-id: 20241121-ge-ian-debug-imx8-clk-tree-bd325aa866f1 Best regards,