From patchwork Sun Aug 30 12:57:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans de Goede X-Patchwork-Id: 11744923 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D8E4C13A4 for ; Sun, 30 Aug 2020 12:58:34 +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 B80A52087D for ; Sun, 30 Aug 2020 12:58:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QViHLW1D" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B80A52087D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CB98A6E2EC; Sun, 30 Aug 2020 12:58:32 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id E02BD6E2EC for ; Sun, 30 Aug 2020 12:58:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1598792310; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cYWhKTISh/u3aMewN0hIMxxIUF++N0gpcMl9YN4NWk8=; b=QViHLW1DoBNaGHnWntqRhZIu42z8wleaETEkoF7M6UqSwXSioahlcA8kXcsgm3G6Yee+Xy fq1EC9YusACX+exErpXS9r2rZiPwKYeVHV9FSz+ERWxaPWdbRfi2RjX40RdHURbKkOpLXc RhgywZeKn1Nfe+3LFY+/LXsjbUtGRNQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-451-FIJRd5iBPn6lR5YznDhDSg-1; Sun, 30 Aug 2020 08:58:25 -0400 X-MC-Unique: FIJRd5iBPn6lR5YznDhDSg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B27691005E60; Sun, 30 Aug 2020 12:58:23 +0000 (UTC) Received: from x1.localdomain.com (ovpn-112-77.ams2.redhat.com [10.36.112.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id 21FF2171C6; Sun, 30 Aug 2020 12:58:20 +0000 (UTC) From: Hans de Goede To: Thierry Reding , =?utf-8?q?Uwe_Kleine-K=C3=B6n?= =?utf-8?q?ig?= , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , =?utf-8?b?VmlsbGUgU3lyasOkbMOk?= , "Rafael J . Wysocki" , Len Brown Date: Sun, 30 Aug 2020 14:57:44 +0200 Message-Id: <20200830125753.230420-9-hdegoede@redhat.com> In-Reply-To: <20200830125753.230420-1-hdegoede@redhat.com> References: <20200830125753.230420-1-hdegoede@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Subject: [Intel-gfx] [PATCH v8 08/17] pwm: crc: Fix period / duty_cycle times being off by a factor of 256 X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pwm@vger.kernel.org, linux-acpi@vger.kernel.org, intel-gfx , dri-devel@lists.freedesktop.org, Andy Shevchenko , Mika Westerberg Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" While looking into adding atomic-pwm support to the pwm-crc driver I noticed something odd, there is a PWM_BASE_CLK define of 6 MHz and there is a clock-divider which divides this with a value between 1-128, and there are 256 duty-cycle steps. The pwm-crc code before this commit assumed that a clock-divider setting of 1 means that the PWM output is running at 6 MHZ, if that is true, where do these 256 duty-cycle steps come from? This would require an internal frequency of 256 * 6 MHz = 1.5 GHz, that seems unlikely for a PMIC which is using a silicon process optimized for power-switching transistors. It is way more likely that there is an 8 bit counter for the duty cycle which acts as an extra fixed divider wrt the PWM output frequency. The main user of the pwm-crc driver is the i915 GPU driver which uses it for backlight control. Lets compare the PWM register values set by the video-BIOS (the GOP), assuming the extra fixed divider is present versus the PWM frequency specified in the Video-BIOS-Tables: Device: PWM Hz set by BIOS PWM Hz specified in VBT Asus T100TA 200 200 Asus T100HA 200 200 Lenovo Miix 2 8 23437 20000 Toshiba WT8-A 23437 20000 So as we can see if we assume the extra division by 256 then the register values set by the GOP are an exact match for the VBT values, where as otherwise the values would be of by a factor of 256. This commit fixes the period / duty_cycle calculations to take the extra division by 256 into account. Reviewed-by: Andy Shevchenko Signed-off-by: Hans de Goede Acked-by: Thierry Reding Acked-by: Thierry Reding --- Changes in v3: - Use NSEC_PER_USEC instead of adding a new (non-sensical) NSEC_PER_MHZ define --- drivers/pwm/pwm-crc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c index 272eeb071147..c056eb9b858c 100644 --- a/drivers/pwm/pwm-crc.c +++ b/drivers/pwm/pwm-crc.c @@ -21,8 +21,8 @@ #define PWM_MAX_LEVEL 0xFF -#define PWM_BASE_CLK 6000000 /* 6 MHz */ -#define PWM_MAX_PERIOD_NS 21333 /* 46.875KHz */ +#define PWM_BASE_CLK_MHZ 6 /* 6 MHz */ +#define PWM_MAX_PERIOD_NS 5461333 /* 183 Hz */ /** * struct crystalcove_pwm - Crystal Cove PWM controller @@ -72,7 +72,7 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm, /* changing the clk divisor, need to disable fisrt */ crc_pwm_disable(c, pwm); - clk_div = PWM_BASE_CLK * period_ns / NSEC_PER_SEC; + clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC); regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, clk_div | PWM_OUTPUT_ENABLE);