From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 2DABEC28D13 for ; Fri, 19 Aug 2022 22:44:02 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4M8cHh4Q0kz3dy2 for ; Sat, 20 Aug 2022 08:44:00 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=G9ItjeqE; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=infradead.org (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org; envelope-from=rdunlap@infradead.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=G9ItjeqE; dkim-atps=neutral Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4M8cH30Yd7z3bxt for ; Sat, 20 Aug 2022 08:43:26 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Sender:Reply-To:Content-ID:Content-Description; bh=goG5LB8namyKTJGHlQDVYOEn/LSWKITP9frCvQXf38Y=; b=G9ItjeqEmkfO7Sedn9n9RCO48B bBIiwJ1kx8hIXNKondte8LHOV/iDX6lfxwRmD24PyeNnDAdIh7VVUXwA0dECCDfxn6lpflz/wjC4o tJbCWaFX+jxoAP12qkpgpkHANjS9A5bnfaNnlxgz2SAiaFwAcGuIeSHvEtkDW7/Rl9bqemZP1KjA3 dvyImPZXGwyiB29OMWx+OctY+IdyMgk7HFSFyH5jC/jh6e245S9HGsQx+CB5pkk/AQ7+nprQ8yrs7 WODHyFNOPzZJ6TU39F+SUBaWGD3s/vnZLZ8EywFnqzfGb2BdZhBy3TVZUmwQq93LvhwFAyK1fG7ah KaHLSYqA==; Received: from [2601:1c0:6280:3f0::a6b3] by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1oPAhz-00D0H0-AT; Fri, 19 Aug 2022 22:43:19 +0000 Message-ID: Date: Fri, 19 Aug 2022 15:43:18 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] powerpc: Add support for early debugging via Serial 16550 console Content-Language: en-US To: =?UTF-8?Q?Pali_Roh=c3=a1r?= References: <20220819211254.22192-1-pali@kernel.org> <35c0ff6a-387d-3c01-66b3-f659cfe67c2a@infradead.org> <20220819223848.lvxakjjzfdjvyqgu@pali> From: Randy Dunlap In-Reply-To: <20220819223848.lvxakjjzfdjvyqgu@pali> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nick Child , linux-kernel@vger.kernel.org, Paul Mackerras , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 8/19/22 15:38, Pali Rohár wrote: > On Friday 19 August 2022 15:34:14 Randy Dunlap wrote: >> Hi-- >> >> On 8/19/22 14:12, Pali Rohár wrote: >>> Currently powerpc early debugging contains lot of platform specific >>> options, but does not support standard UART / serial 16550 console. >>> >>> Later legacy_serial.c code supports registering UART as early debug console >>> from device tree but it is not early during booting, but rather later after >>> machine description code finishes. >>> >>> So for real early debugging via UART is current code unsuitable. >>> >>> Add support for new early debugging option CONFIG_PPC_EARLY_DEBUG_16550 >>> which enable Serial 16550 console on address defined by new option >>> CONFIG_PPC_EARLY_DEBUG_16550_PHYSADDR and by stride by option >>> CONFIG_PPC_EARLY_DEBUG_16550_STRIDE. >>> >>> With this change it is possible to debug powerpc machine descriptor code. >>> For example this early debugging code can print on serial console also >>> "No suitable machine description found" error which is done before >>> legacy_serial.c code. >>> >>> Signed-off-by: Pali Rohár >>> --- >>> Tested on P2020 board. It allowed me do debug and implement this patch series: >>> https://lore.kernel.org/linuxppc-dev/20220819191557.28116-1-pali@kernel.org/ >>> --- >>> arch/powerpc/Kconfig.debug | 14 ++++++++++++++ >>> arch/powerpc/include/asm/udbg.h | 1 + >>> arch/powerpc/kernel/udbg.c | 2 ++ >>> arch/powerpc/kernel/udbg_16550.c | 33 ++++++++++++++++++++++++++++++++ >>> 4 files changed, 50 insertions(+) >>> >>> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug >>> index 9f363c143d86..a4e7d90a45d2 100644 >>> --- a/arch/powerpc/Kconfig.debug >>> +++ b/arch/powerpc/Kconfig.debug >>> @@ -276,6 +276,11 @@ config PPC_EARLY_DEBUG_OPAL_HVSI >>> Select this to enable early debugging for the PowerNV platform >>> using an "hvsi" console >>> >>> +config PPC_EARLY_DEBUG_16550 >>> + bool "Serial 16550" >>> + help >>> + Select this to enable early debugging via Serial 16550 console >>> + >>> config PPC_EARLY_DEBUG_MEMCONS >>> bool "In memory console" >>> help >>> @@ -355,6 +360,15 @@ config PPC_EARLY_DEBUG_CPM_ADDR >>> platform probing is done, all platforms selected must >>> share the same address. >>> >>> +config PPC_EARLY_DEBUG_16550_PHYSADDR >>> + hex "Early debug Serial 16550 physical address" >>> + depends on PPC_EARLY_DEBUG_16550 >> >> Is there any chance that you could provide a default value here >> so that 'make olddefconfig' does not end up like it does >> without having a default value? > > No. Because there is not any default value. Physical address of 16550 is > hardly HW dependent. Possibly also bootloader dependent (if it can remap > peripherals to different physical addresses). > > User _has to_ specify correct physical address if want to use early > debug 16550 console. OK, we'll see if it ever causes a real problem then... >> CONFIG_PPC_EARLY_DEBUG_16550=y >> # CONFIG_PPC_EARLY_DEBUG_MEMCONS is not set >> CONFIG_PPC_EARLY_DEBUG_16550_PHYSADDR= >> CONFIG_PPC_EARLY_DEBUG_16550_STRIDE=1 >> >> which then causes a kconfig prompt when starting >> the build... > > Cannot we set somehow that PPC_EARLY_DEBUG_16550 would be disabled by > default when upgrading defconfig? Don't know about that. Thanks. -- ~Randy