From patchwork Fri Sep 8 16:51:16 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gatien CHEVALLIER X-Patchwork-Id: 721284 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 18AE9EE801F for ; Fri, 8 Sep 2023 16:53:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245298AbjIHQxd (ORCPT ); Fri, 8 Sep 2023 12:53:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50206 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245242AbjIHQx1 (ORCPT ); Fri, 8 Sep 2023 12:53:27 -0400 Received: from mx07-00178001.pphosted.com (mx08-00178001.pphosted.com [91.207.212.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FDA2210C; Fri, 8 Sep 2023 09:52:57 -0700 (PDT) Received: from pps.filterd (m0046661.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.17.1.22/8.17.1.22) with ESMTP id 388Fj6TW020297; Fri, 8 Sep 2023 18:52:43 +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=QUriKgAIAV2H+EDbut4I3imj3RNChpoKLH5/B3MDzDQ=; b=Fh ULsVW+1ljOHKV0Bwjg4slbRk5U5dnaBCgGReKdYCkoRGBykyRKexPGSug2E72ZtR +aBQrkBYe4Nsl9Au+81oNohswaKCIX/A70LjxsYXKTpMFONNoOM2rUxZiUTBuVDQ N8RalLjjoMEm5xWxw1QLvlLNCxMuGxETiDNOAyAJaBR0A9q0NdueHLthKctUYQxM 2vEqUU1uQjnVxWvkbhjpe6R86GYy6Y61H8BvrfAJ5qJ/HqluBdgv0M5yg7GF4sC3 in84eGZ4AFn5eb3nupY3kXiTMZWVIA81N5zXxgrvLEZ0TiAb2ZA7PnzTM6fTcEH7 0lYWbfdWayqyd+n90j1g== 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 3suuxcndj1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 08 Sep 2023 18:52:43 +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 5AA9C10004B; Fri, 8 Sep 2023 18:52:43 +0200 (CEST) Received: from Webmail-eu.st.com (shfdag1node1.st.com [10.75.129.69]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 4C58E209EF6; Fri, 8 Sep 2023 18:52:43 +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 15.1.2507.21; Fri, 8 Sep 2023 18:52:42 +0200 From: Gatien Chevallier To: Olivia Mackall , Herbert Xu , Rob Herring , Krzysztof Kozlowski , Maxime Coquelin , Alexandre Torgue CC: Lionel Debieve , , , , , , Gatien Chevallier Subject: [PATCH 06/10] hwrng: stm32 - restrain RNG noise source clock Date: Fri, 8 Sep 2023 18:51:16 +0200 Message-ID: <20230908165120.730867-7-gatien.chevallier@foss.st.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230908165120.730867-1-gatien.chevallier@foss.st.com> References: <20230908165120.730867-1-gatien.chevallier@foss.st.com> MIME-Version: 1.0 X-Originating-IP: [10.201.20.32] X-ClientProxiedBy: EQNCAS1NODE4.st.com (10.75.129.82) To SHFDAG1NODE1.st.com (10.75.129.69) X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.601,FMLib:17.11.176.26 definitions=2023-09-08_12,2023-09-05_01,2023-05-22_02 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.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 3d32e0f4baef..3b77f1fe6aea 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[] = {