From patchwork Mon Apr 4 08:58:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Ivan T. Ivanov" X-Patchwork-Id: 12800017 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC995C433F5 for ; Mon, 4 Apr 2022 08:59:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242238AbiDDJBA (ORCPT ); Mon, 4 Apr 2022 05:01:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45754 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235945AbiDDJBA (ORCPT ); Mon, 4 Apr 2022 05:01:00 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9FF4725C53 for ; Mon, 4 Apr 2022 01:59:04 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 2AFD1210F5; Mon, 4 Apr 2022 08:59:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1649062743; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=kzl0YogUV15ZNu+Gdvf0m+yPGkbCIWbej2o9Y3VSOdc=; b=vLC7UcdLc3ZXqwkVSqEDgtOzlkIp/H6wJm0577gl1hcl6HOQ6vY9Iy2Byr103ZnSi4qeB4 JChP/JLUNfQtDvhjFx87C2MMczCiXQXpDMfvSHo0KeDpqN9TRQOQbwukHpqVFQaVEQUTiG yGpGDn1/qVmWhKJdh1sfShrc3bpA1CI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1649062743; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=kzl0YogUV15ZNu+Gdvf0m+yPGkbCIWbej2o9Y3VSOdc=; b=Rc/R+dxIeIUy3cVs8M3bzxbIqzpX6WBxi60o88EE6z2nS+GHUzUwQmN44GcF7DxfcEad5l BK8mpf6d/y27kXAA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 140BD13216; Mon, 4 Apr 2022 08:59:03 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id +8uWBFezSmKNDwAAMHmgww (envelope-from ); Mon, 04 Apr 2022 08:59:03 +0000 From: "Ivan T. Ivanov" To: Michael Turquette , Stephen Boyd Cc: Phil Elwell , Nicolas Saenz Julienne , Florian Fainelli , Ray Jui , Scott Branden , Maxime Ripard , Martin Blumenstingl , bcm-kernel-feedback-list@broadcom.com, linux-clk@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, "Ivan T. Ivanov" Subject: [PATCH] clk: bcm2835: Round UART input clock up Date: Mon, 4 Apr 2022 11:58:22 +0300 Message-Id: <20220404085822.84135-1-iivanov@suse.de> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org The UART clock is initialised to be as close to the requested frequency as possible without exceeding it. Now that there is a clock manager that returns the actual frequencies, an expected 48MHz clock is reported as 47999625. If the requested baudrate == requested clock/16, there is no headroom and the slight reduction in actual clock rate results in failure. If increasing a clock by less than 0.1% changes it from ..999.. to ..000.., round it up. This is reworked version of a downstream fix: https://github.com/raspberrypi/linux/commit/ab3f1b39537f6d3825b8873006fbe2fc5ff057b7 Cc: Phil Elwell Signed-off-by: Ivan T. Ivanov Reported-by: kernel test robot --- drivers/clk/bcm/clk-bcm2835.c | 30 ++++++++++++++++++++++++++++-- 1 file changed, 28 insertions(+), 2 deletions(-) diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c index 3ad20e75fd23..f293cde427b7 100644 --- a/drivers/clk/bcm/clk-bcm2835.c +++ b/drivers/clk/bcm/clk-bcm2835.c @@ -502,6 +502,8 @@ struct bcm2835_clock_data { bool low_jitter; u32 tcnt_mux; + + bool round_up; }; struct bcm2835_gate_data { @@ -992,12 +994,30 @@ static long bcm2835_clock_rate_from_divisor(struct bcm2835_clock *clock, return temp; } +unsigned long bcm2835_clock_round(unsigned long clk) +{ + unsigned long scaler; + + /* + * If increasing a clock by less than 0.1% changes it + * from ..999.. to ..000.., round up. + */ + scaler = 1; + while (scaler * 100000 < clk) + scaler *= 10; + if ((clk + scaler - 1) / scaler % 1000 == 0) + clk = (clk / scaler + 1) * scaler; + + return clk; +} + static unsigned long bcm2835_clock_get_rate(struct clk_hw *hw, unsigned long parent_rate) { struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw); struct bcm2835_cprman *cprman = clock->cprman; const struct bcm2835_clock_data *data = clock->data; + unsigned long rate; u32 div; if (data->int_bits == 0 && data->frac_bits == 0) @@ -1005,7 +1025,12 @@ static unsigned long bcm2835_clock_get_rate(struct clk_hw *hw, div = cprman_read(cprman, data->div_reg); - return bcm2835_clock_rate_from_divisor(clock, parent_rate, div); + rate = bcm2835_clock_rate_from_divisor(clock, parent_rate, div); + + if (data->round_up) + rate = bcm2835_clock_round(rate); + + return rate; } static void bcm2835_clock_wait_busy(struct bcm2835_clock *clock) @@ -2142,7 +2167,8 @@ static const struct bcm2835_clk_desc clk_desc_array[] = { .div_reg = CM_UARTDIV, .int_bits = 10, .frac_bits = 12, - .tcnt_mux = 28), + .tcnt_mux = 28, + .round_up = true), /* TV encoder clock. Only operating frequency is 108Mhz. */ [BCM2835_CLOCK_VEC] = REGISTER_PER_CLK(