From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Tue, 18 Mar 2025 12:26:28 +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 1tuV5Z-00119N-0W for lore@lore.pengutronix.de; Tue, 18 Mar 2025 12:26:28 +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 1tuV5X-0006N7-UG for lore@pengutronix.de; Tue, 18 Mar 2025 12:26:28 +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=+6i/pdrLMm1VmLqnXJ7PLtbgW0l/3WvMw0zGkrM9b+g=; b=e9u+GOqGCCUZ/hdPXqsDyfA3Vh o5vdAcboeyJFCihi2djuop+7N4QCXKFMB27QLb9h3RL1v6ivFVWOI9CkRJYq+i0yPSYiU226Yj8Yi TCTA2WX5nkiDIeUmXcK+TUfNEgF7E2LD0GU7S63WqzMUyQO1Os2PHVm6sHfFyr5mc3Ba+HLAp0/UJ iUKvvN/lD05oAbDq7X9M9il53VC3Amn0lANofTgoz+QomLfxVw5xfjv/bzjWP1a0n38WQeCBdKpRy XM9PVqq15wbLGEjXqrpRKSLsYJ6/HGJFFU9st/CPrToiaOiB5xQex6AVeYtIJKSvOJ001aHFUGIpw HdJ7ftQQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tuV57-00000005ikp-38IK; Tue, 18 Mar 2025 11:26:01 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tuV3l-00000005iYO-0K0U for barebox@lists.infradead.org; Tue, 18 Mar 2025 11:24:38 +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 1tuV3j-0005w7-RJ; Tue, 18 Mar 2025 12:24:35 +0100 Message-ID: Date: Tue, 18 Mar 2025 12:24:35 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Sascha Hauer Cc: barebox@lists.infradead.org References: <20250318082507.419785-1-a.fatoum@pengutronix.de> <20250318082507.419785-3-a.fatoum@pengutronix.de> From: Ahmad Fatoum Content-Language: en-US, de-DE, de-BE In-Reply-To: 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-20250318_042437_119775_06ADFE8D X-CRM114-Status: GOOD ( 31.87 ) 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=-5.4 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 3/4] amba: support masking data abort during identification 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) Hello Sascha, On 3/18/25 12:04, Sascha Hauer wrote: > On Tue, Mar 18, 2025 at 09:25:06AM +0100, Ahmad Fatoum wrote: >> Registration of an AMBA device requires reading its pid and cid >> registers after turning on the device. This is the first I/O done to the >> device and may end up crashing if the device tree doesn't describe >> the correct clock and power domains or if a previous boot stage >> should've enabled them, but didn't. >> >> This is not a likely issue, but when it happens it crashes the system >> annoyingly early during device tree populating. >> >> Add a symbol that masks the data abort exception around the >> identification code to turn the crash into an error message instead. > > Do we need to make this optional? I could imagine I find out about the > existence of this option only after having traced the issue down to the > exact lines of code in which case I won't need the option anymore. If it turns out to be needed for more platforms, we can consider making it visible by default, but currently I think its of rather limited use case. Another way would be disabling the node in the barebox DT, but I don't want to the Qemu virt DTs to diverge. Cheers, Ahmad > > Sascha > >> >> Signed-off-by: Ahmad Fatoum >> --- >> drivers/amba/Kconfig | 19 +++++++++++++++++++ >> drivers/amba/bus.c | 12 +++++++++++- >> 2 files changed, 30 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/amba/Kconfig b/drivers/amba/Kconfig >> index 444d4ce7435c..be5e053f4b84 100644 >> --- a/drivers/amba/Kconfig >> +++ b/drivers/amba/Kconfig >> @@ -1,3 +1,22 @@ >> # SPDX-License-Identifier: GPL-2.0-only >> config ARM_AMBA >> bool >> + >> +config ARM_AMBA_DABT_MASK >> + bool >> + prompt "Mask data abort while identifying AMBA devices" if COMPILE_TEST >> + depends on ARM_AMBA && ARCH_HAS_DATA_ABORT_MASK >> + help >> + Registration of an AMBA device requires reading its pid and cid >> + registers after turning on the device, which can involve enabling >> + clocks, deasserting resets and powering on power domains. >> + In some cases, these resources are not available to barebox running >> + in the normal world and thus need to be setup by a previous >> + stage bootloader running in the secure world. >> + If such setup doesn't happen, accessing devices may lead to >> + a data abort or complete system hang. >> + >> + As a workaround for the former case, this option can be enabled >> + to gracefully handle data aborts during readout of the PID/CID >> + registers. The proper solution is fixing your first stage >> + bootloader or allow barebox access to the missing resources. >> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c >> index 6463366fafc5..5ed8336e6124 100644 >> --- a/drivers/amba/bus.c >> +++ b/drivers/amba/bus.c >> @@ -10,6 +10,7 @@ >> #include >> #include >> #include >> +#include >> >> #define to_amba_driver(d) container_of(d, struct amba_driver, drv) >> >> @@ -132,6 +133,9 @@ int amba_device_add(struct amba_device *dev) >> if (ret == 0) { >> u32 pid, cid; >> >> + if (IS_ENABLED(CONFIG_ARM_AMBA_DABT_MASK)) >> + data_abort_mask(); >> + >> /* >> * Read pid and cid based on size of resource >> * they are located at end of region >> @@ -139,8 +143,14 @@ int amba_device_add(struct amba_device *dev) >> pid = amba_device_get_pid(tmp, size); >> cid = amba_device_get_cid(tmp, size); >> >> - if (cid == AMBA_CID) >> + if (IS_ENABLED(CONFIG_ARM_AMBA_DABT_MASK) && data_abort_unmask()) { >> + dev_err(amba_bustype.dev, >> + "data abort during MMIO read of PID/CID for %pOF\n", >> + dev->dev.of_node); >> + ret = -EFAULT; >> + } else if (cid == AMBA_CID) { >> dev->periphid = pid; >> + } >> >> if (!dev->periphid) >> ret = -ENODEV; >> -- >> 2.39.5 >> >> >> >