From patchwork Thu Nov 18 14:03:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Naveen Naidu X-Patchwork-Id: 12627095 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABF39C433EF for ; Thu, 18 Nov 2021 14:05:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8CDE160EFD for ; Thu, 18 Nov 2021 14:05:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232213AbhKROIT (ORCPT ); Thu, 18 Nov 2021 09:08:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37772 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232229AbhKROIH (ORCPT ); Thu, 18 Nov 2021 09:08:07 -0500 Received: from mail-pg1-x531.google.com (mail-pg1-x531.google.com [IPv6:2607:f8b0:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B23C7C061200; Thu, 18 Nov 2021 06:05:07 -0800 (PST) Received: by mail-pg1-x531.google.com with SMTP id r5so5412285pgi.6; Thu, 18 Nov 2021 06:05:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=zxXrUZht15oO1Xjz6QWdqaAcujYVEC+9jBLeu7+7g0c=; b=HbXpWZrZFoaUh8ToyYcOr4IeJCt9Wtb/Ii4qTWagMTuHX7bBJ408OnaIHcxI6Aydah JcN5EhV7L+2xpGF7TR51D0VZb585s/LREfwS14xSPHw2V/jvXmopFLGnbqor/FNbm8DY Jf/IDZK+dS22PSV9/J4C5iuyEPNNVEkZVb8S+eueWHOek3vTdeiBGsN+6NhdGO4ZcoLF GJtCPA5N2xZQ165JR+wTN72S8dX21PRK+X6tlSksm0DWdb3ajFZkrNYdbqpc5kgjKvhT XPqraYIqNUphptmr1sD7LurQPDjPHlIaXrUBAvmJcZ30mG1iQFLMn54+fGN4mG8m5IkB Tj8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=zxXrUZht15oO1Xjz6QWdqaAcujYVEC+9jBLeu7+7g0c=; b=0lbyUm02hy9hOb8mR4Z7YZ+D/4siFPaF+h0KVSxnQ2ibbZZ+SQgj7F110agsmvwgIc oglBGkqyaa7ns83h6xiCQ4xdX8OokpfSBq/5oPGAq96ZhEFSG2FCqnwS/y1+Z4vSmf9C +4o8cNZ+21WxzBIrYTc7BBz87qayy/5OQ2+rJH0XPMNU3/+OL6wkgql7PLg2YsjgTBgN irea1WypTgEzdCsG49bnsmNz9068dBkEOzkt1jK7tqTKSCTJdBkVfR9+cHt6d7yrhkSc zX0GRGP+5PFF5uTcQ+pTgjpx+GNgaxCC3abPzpGfENsV6tm/CdcXphfysILNyvqAdp3C Layw== X-Gm-Message-State: AOAM531VM+HYOUyWUKP35b6onOJ1SEL10Vh/39fBuY2sbUUQpEzpHEwx 1Nl63GUf3z/dbskSOkX8+CI= X-Google-Smtp-Source: ABdhPJwOXyE6HEQbNhPVgekg9gPYV7L5WppEDsCgRjqxmDA8X9Db0i/xJwXn6bbQv5oaIkUB7CnPhw== X-Received: by 2002:a63:2c53:: with SMTP id s80mr11543263pgs.6.1637244307202; Thu, 18 Nov 2021 06:05:07 -0800 (PST) Received: from localhost.localdomain ([2406:7400:63:2c47:5ffe:fc34:61f0:f1ea]) by smtp.gmail.com with ESMTPSA id x14sm2822878pjl.27.2021.11.18.06.05.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Nov 2021 06:05:06 -0800 (PST) From: Naveen Naidu To: bhelgaas@google.com Cc: Naveen Naidu , linux-kernel-mentees@lists.linuxfoundation.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, Rob Herring Subject: [PATCH v4 04/25] PCI: Remove redundant error fabrication when device read fails Date: Thu, 18 Nov 2021 19:33:14 +0530 Message-Id: <1b2edb060cf19b45f70645b331e6c08c9ba798c0.1637243717.git.naveennaidu479@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org An MMIO read from a PCI device that doesn't exist or doesn't respond causes a PCI error. There's no real data to return to satisfy the CPU read, so most hardware fabricates ~0 data. The host controller drivers sets the error response values (~0) and returns an error when faulty hardware read occurs. But the error response value (~0) is already being set in PCI_OP_READ and PCI_USER_READ_CONFIG whenever a read by host controller driver fails. Thus, it's no longer necessary for the host controller drivers to fabricate any error response. This helps unify PCI error response checking and make error check consistent and easier to find. Reviewed-by: Rob Herring Signed-off-by: Naveen Naidu --- drivers/pci/access.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/pci/access.c b/drivers/pci/access.c index e1add90494ec..a92637627845 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -83,10 +83,8 @@ int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn, void __iomem *addr; addr = bus->ops->map_bus(bus, devfn, where); - if (!addr) { - *val = ~0; + if (!addr) return PCIBIOS_DEVICE_NOT_FOUND; - } if (size == 1) *val = readb(addr); @@ -125,10 +123,8 @@ int pci_generic_config_read32(struct pci_bus *bus, unsigned int devfn, void __iomem *addr; addr = bus->ops->map_bus(bus, devfn, where & ~0x3); - if (!addr) { - *val = ~0; + if (!addr) return PCIBIOS_DEVICE_NOT_FOUND; - } *val = readl(addr);