From patchwork Thu Sep 21 08:02:58 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gatien CHEVALLIER X-Patchwork-Id: 13393754 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 D467AE706E5 for ; Thu, 21 Sep 2023 08:05:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=hIf6Mu7VbirYU/d25IRy9WuuYoZA7asdyn5gqRBuA7I=; b=gLlQ/DVvfDzHkn IvT4LYjP8Bm29UdjyXBj2KOMqWcaJuYIDQ2dDxeNxhycebU8QQnN+8vJ1ICyRcF4jlOVKMuj5NU6H j+8FXNwMO5l14cVhxonZrZwFPFTZO8hFhEhViQi+QMIim1arN2tOr+O9+i9VIQgfj8w11jM8lqtIr iEmrsr0ONIVdXxkm/bq0nz9nWW0wjTCIwGfZZZbS8IighrgOV4Iwu19qq3fOcciVPFOpnOhHNWHse N9fEjVuVcD5Z6E2PF29ecDYts/1Szb76rswP6/lTTFZrFdC4O+1TI5a9DeMD4vGgBUWV7yaJPjksY x8bXPsAZhx7MVQDcfulA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qjEg1-005RmY-0N; Thu, 21 Sep 2023 08:04:45 +0000 Received: from mx07-00178001.pphosted.com ([185.132.182.106]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qjEfw-005Rjh-01 for linux-arm-kernel@lists.infradead.org; Thu, 21 Sep 2023 08:04:42 +0000 Received: from pps.filterd (m0241204.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.17.1.22/8.17.1.22) with ESMTP id 38L5uxXN026704; Thu, 21 Sep 2023 10:04:24 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=foss.st.com; h= from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding:content-type; s= selector1; bh=+tmt8dbtTqSwHcdueUDhtt/63vObb0tlhOMDJTofgcc=; b=7E sWR96nRMkwANBcO+iU4lBtxq8/NLnlYlLForqxgsbQ6FkLvmThjvAl4yAkDQNYPu XBNUH2bYOsiEqL6pGp0IzGlOxPY8w3TbyE3h1kxZ00cqrqh3ccd2IdUkhF5Fyufw ABlgUz/gfX/mrNt4ZfH7uzlqjcQ3OhN4OTwoviIqHYBI7TwW1JDPjLQU+bRWXldU HoKxejVVJXGynNESISv5EnajSGcXqtQ7m2D4xjDol7t+j/iN0ix4grITf4coM0/T RTvYQXFfn04LoE/K4ePKpX9cZpx0r+4++2eUILsLieNHflkRIYvxUe89ag6y+fhF PpPllhTDE81p20RjX6VA== Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com (PPS) with ESMTPS id 3t53px31mr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 21 Sep 2023 10:04:24 +0200 (MEST) Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 13BEA100057; Thu, 21 Sep 2023 10:04:23 +0200 (CEST) Received: from Webmail-eu.st.com (shfdag1node1.st.com [10.75.129.69]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 0BC4C21863D; Thu, 21 Sep 2023 10:04:23 +0200 (CEST) Received: from localhost (10.201.20.32) by SHFDAG1NODE1.st.com (10.75.129.69) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Thu, 21 Sep 2023 10:04:22 +0200 From: Gatien Chevallier To: Olivia Mackall , Herbert Xu , Rob Herring , Krzysztof Kozlowski , Maxime Coquelin , Alexandre Torgue CC: Lionel Debieve , , , , , , Gatien Chevallier Subject: [PATCH v3 6/9] hwrng: stm32 - restrain RNG noise source clock Date: Thu, 21 Sep 2023 10:02:58 +0200 Message-ID: <20230921080301.253563-7-gatien.chevallier@foss.st.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230921080301.253563-1-gatien.chevallier@foss.st.com> References: <20230921080301.253563-1-gatien.chevallier@foss.st.com> MIME-Version: 1.0 X-Originating-IP: [10.201.20.32] X-ClientProxiedBy: SHFCAS1NODE1.st.com (10.75.129.72) To SHFDAG1NODE1.st.com (10.75.129.69) X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.980,Hydra:6.0.601,FMLib:17.11.176.26 definitions=2023-09-21_06,2023-09-20_01,2023-05-22_02 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230921_010440_553456_5B8842CA X-CRM114-Status: GOOD ( 19.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org For NIST certification the noise source sampling may need to be restrained. This change implements an algorithm that gets the rate of the RNG clock and apply the correct value in CLKDIV field in RNG_CR register to force the RNG clock rate to be "max_clock_rate" maximum. As it is platform-specific, implement it as a compat data. Signed-off-by: Gatien Chevallier --- drivers/char/hw_random/stm32-rng.c | 34 ++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c index 9dac177d5286..819f062f454d 100644 --- a/drivers/char/hw_random/stm32-rng.c +++ b/drivers/char/hw_random/stm32-rng.c @@ -23,11 +23,13 @@ #define RNG_CR_CONFIG1 GENMASK(11, 8) #define RNG_CR_NISTC BIT(12) #define RNG_CR_CONFIG2 GENMASK(15, 13) +#define RNG_CR_CLKDIV_SHIFT 16 +#define RNG_CR_CLKDIV GENMASK(19, 16) #define RNG_CR_CONFIG3 GENMASK(25, 20) #define RNG_CR_CONDRST BIT(30) #define RNG_CR_CONFLOCK BIT(31) #define RNG_CR_ENTROPY_SRC_MASK (RNG_CR_CONFIG1 | RNG_CR_NISTC | RNG_CR_CONFIG2 | RNG_CR_CONFIG3) -#define RNG_CR_CONFIG_MASK (RNG_CR_ENTROPY_SRC_MASK | RNG_CR_CED) +#define RNG_CR_CONFIG_MASK (RNG_CR_ENTROPY_SRC_MASK | RNG_CR_CED | RNG_CR_CLKDIV) #define RNG_SR 0x04 #define RNG_SR_DRDY BIT(0) @@ -46,6 +48,7 @@ #define RNG_NB_RECOVER_TRIES 3 struct stm32_rng_data { + uint max_clock_rate; u32 cr; u32 nscr; u32 htcr; @@ -238,6 +241,28 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) return retval || !wait ? retval : -EIO; } +static uint stm32_rng_clock_freq_restrain(struct hwrng *rng) +{ + struct stm32_rng_private *priv = + container_of(rng, struct stm32_rng_private, rng); + unsigned long clock_rate = 0; + uint clock_div = 0; + + clock_rate = clk_get_rate(priv->clk); + + /* + * Get the exponent to apply on the CLKDIV field in RNG_CR register + * No need to handle the case when clock-div > 0xF as it is physically + * impossible + */ + while ((clock_rate >> clock_div) > priv->data->max_clock_rate) + clock_div++; + + pr_debug("RNG clk rate : %lu\n", clk_get_rate(priv->clk) >> clock_div); + + return clock_div; +} + static int stm32_rng_init(struct hwrng *rng) { struct stm32_rng_private *priv = @@ -259,8 +284,11 @@ static int stm32_rng_init(struct hwrng *rng) * 0 is an invalid value as it disables all entropy sources. */ if (priv->data->has_cond_reset && priv->data->cr) { + uint clock_div = stm32_rng_clock_freq_restrain(rng); + reg &= ~RNG_CR_CONFIG_MASK; - reg |= RNG_CR_CONDRST | (priv->data->cr & RNG_CR_ENTROPY_SRC_MASK); + reg |= RNG_CR_CONDRST | (priv->data->cr & RNG_CR_ENTROPY_SRC_MASK) | + (clock_div << RNG_CR_CLKDIV_SHIFT); if (priv->ced) reg &= ~RNG_CR_CED; else @@ -360,6 +388,7 @@ static const struct dev_pm_ops stm32_rng_pm_ops = { static const struct stm32_rng_data stm32mp13_rng_data = { .has_cond_reset = true, + .max_clock_rate = 48000000, .cr = 0x00F00D00, .nscr = 0x2B5BB, .htcr = 0x969D, @@ -367,6 +396,7 @@ static const struct stm32_rng_data stm32mp13_rng_data = { static const struct stm32_rng_data stm32_rng_data = { .has_cond_reset = false, + .max_clock_rate = 3000000, }; static const struct of_device_id stm32_rng_match[] = {