From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Mon, 13 Nov 2023 16:04:38 +0100 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1r2YUP-00A9KP-1C for lore@lore.pengutronix.de; Mon, 13 Nov 2023 16:04:37 +0100 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1r2YUP-00080k-8r for lore@pengutronix.de; Mon, 13 Nov 2023 16:04:37 +0100 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=HwAV6/zK5VdGtuQ0hk+370MfYRTKYbXDeITK9IilNHI=; b=WiE93KJNS+XZ28OT6tKvRPlvmF MQZasseTxQEhyjCX6PxV6gWzgIdbzo2d675MHLlVpG8Hpu063g5zXfXdBGypTOf4oDEmXHQbD0EcJ n939nNKWLymaNGcHw3JMSN+95vfDEmEV3MuZSAwhGWdH1LleJWySis2CmMwC0mATftux4R+n4xU+k p7vPdECrVby2ZnhbW1lSbHtJnWy+jS8XU3pEekFJmT+tZcXRXiWbLYbfDcSiOi4fZKKVg2f3pkUtz XcJyLh7eu4rTe6bCRePhLey/CHFmtRCIgT3hzFJZYLa6sGcRYh7AP63XV1BHFEH52HX7gSyaDRnI/ zRfwaYJg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r2YSw-00ECTB-1R; Mon, 13 Nov 2023 15:03:06 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1r2YSs-00ECSf-00 for barebox@lists.infradead.org; Mon, 13 Nov 2023 15:03:04 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1r2YSn-0007mP-NV; Mon, 13 Nov 2023 16:02:57 +0100 Message-ID: <546aba5d-d506-52fd-de23-6bc12805ddd4@pengutronix.de> Date: Mon, 13 Nov 2023 16:02:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Content-Language: en-US To: Sascha Hauer Cc: barebox@lists.infradead.org References: <20231109114707.1354502-1-a.fatoum@pengutronix.de> <20231113130350.GS3359458@pengutronix.de> From: Ahmad Fatoum In-Reply-To: <20231113130350.GS3359458@pengutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231113_070302_038520_ED25CCE6 X-CRM114-Status: GOOD ( 29.79 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-6.9 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 1/2] console: provide best-effort clk_get_for_console helper X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) On 13.11.23 14:03, Sascha Hauer wrote: > On Thu, Nov 09, 2023 at 12:47:06PM +0100, Ahmad Fatoum wrote: >> From: Ahmad Fatoum >> >> clk_get will return -EPROBE_DEFER if clock provider hasn't yet been >> probed. In a system with deep probe enabled, dependencies are probed >> on demand, so a -EPROBE_DEFER return is final and the console probe >> will never succeed. >> >> CONFIG_DEBUG_LL is often used to debug this, but because the low-level >> console is not interactive, it's a bit cumbersome. Improve upon this a >> bit, by providing a clk_get_for_console helper that returns NULL if and >> only if we are sure that a clock provider will not be probed. >> >> In that case, the driver can skip code paths initialization code and >> baud rate setting dependent on having access to the clock and still >> register a console that reuses what was set up by CONFIG_DEBUG_LL. >> >> Signed-off-by: Ahmad Fatoum >> --- >> include/console.h | 26 ++++++++++++++++++++++++++ >> include/linux/clk.h | 21 +++++++++++++++++++++ >> 2 files changed, 47 insertions(+) >> >> diff --git a/include/console.h b/include/console.h >> index 586b68f73301..b8c901801e9f 100644 >> --- a/include/console.h >> +++ b/include/console.h >> @@ -8,6 +8,7 @@ >> #define _CONSOLE_H_ >> >> #include >> +#include >> #include >> #include >> #include >> @@ -208,4 +209,29 @@ static inline void console_ctrlc_allow(void) { } >> static inline void console_ctrlc_forbid(void) { } >> #endif >> >> +/** >> + * clk_get_for_console - get clock, ignoring known unavailable clock controller >> + * @dev: device for clock "consumer" >> + * @id: clock consumer ID >> + * >> + * Return: a struct clk corresponding to the clock producer, a >> + * valid IS_ERR() condition containing errno or NULL if it could >> + * be determined that the clock producer will never be probed in >> + * absence of modules. The NULL return allows serial drivers to >> + * skip clock handling and rely on CONFIG_DEBUG_LL. >> + */ >> +static inline struct clk *clk_get_for_console(struct device *dev, const char *id) >> +{ >> + struct clk *clk; >> + >> + if (!IS_ENABLED(CONFIG_DEBUG_LL)) >> + return clk_get(dev, id); > > There are several SoCs out there where the UART is enabled by the ROM > already, on these we don't need to have CONFIG_DEBUG_LL enabled for a > working UART. Those SoCs can still implement CONFIG_DEBUG_LL and just skip the initialization step. > Maybe testing for the UART enable bit in probe() would be a better > indication that the UART is already in a working state? If clk turns out to be not enabled, system would hang on e.g. i.MX. This is a mere debugging measure for SoCs with complex clock controllers backed by firmware, so I think having to enable CONFIG_DEBUG_LL to use is acceptable. Cheers, Ahmad > > Sascha > >> + >> + clk = clk_get_if_available(dev, id); >> + if (clk == NULL) >> + dev_warn(dev, "couldn't get clock (ignoring)\n"); >> + >> + return clk; >> +} >> + >> #endif >> diff --git a/include/linux/clk.h b/include/linux/clk.h >> index 61b4ff3127cf..f505f18a75c0 100644 >> --- a/include/linux/clk.h >> +++ b/include/linux/clk.h >> @@ -14,6 +14,7 @@ >> #include >> #include >> #include >> +#include >> #include >> >> struct device; >> @@ -982,4 +983,24 @@ static inline struct clk *clk_get_enabled(struct device *dev, const char *id) >> return clk; >> } >> >> +/** >> + * clk_get_if_available - get clock, ignoring known unavailable clock controller >> + * @dev: device for clock "consumer" >> + * @id: clock consumer ID >> + * >> + * Return: a struct clk corresponding to the clock producer, a >> + * valid IS_ERR() condition containing errno or NULL if it could >> + * be determined that the clock producer will never be probed in >> + * absence of modules. >> + */ >> +static inline struct clk *clk_get_if_available(struct device *dev, const char *id) >> +{ >> + struct clk *clk = clk_get(dev, id); >> + >> + if (clk == ERR_PTR(-EPROBE_DEFER) && deep_probe_is_supported()) >> + return NULL; >> + >> + return clk; >> +} >> + >> #endif >> -- >> 2.39.2 >> >> >> > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |