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(dynamic-2a01-0c23-c58e-b900-c905-524d-7524-40e1.c23.pool.telefonica.de. [2a01:c23:c58e:b900:c905:524d:7524:40e1]) by smtp.googlemail.com with ESMTPSA id hf15-20020a1709072c4f00b008f89953b761sm4466209ejc.3.2023.05.11.13.17.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 May 2023 13:17:22 -0700 (PDT) Message-ID: <7bb6e2c9-835c-c8d9-f8a5-baa3d3b03b12@gmail.com> Date: Thu, 11 May 2023 22:17:18 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Content-Language: en-US To: Lukas Wunner Cc: =?UTF-8?Q?Ilpo_J=c3=a4rvinen?= , linux-pci@vger.kernel.org, Bjorn Helgaas , Rob Herring , Lorenzo Pieralisi , Krzysztof Wilczy??ski , nic_swsd@realtek.com, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20230511131441.45704-1-ilpo.jarvinen@linux.intel.com> <20230511131441.45704-15-ilpo.jarvinen@linux.intel.com> <98b3b70a-86c0-78c0-b734-0764bb5a21fc@gmail.com> <20230511200244.GA31598@wunner.de> From: Heiner Kallweit Subject: Re: [PATCH 14/17] r8169: Use pcie_lnkctl_clear_and_set() for changing LNKCTL In-Reply-To: <20230511200244.GA31598@wunner.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 11.05.2023 22:02, Lukas Wunner wrote: > On Thu, May 11, 2023 at 09:49:52PM +0200, Heiner Kallweit wrote: >> On 11.05.2023 15:14, Ilpo Järvinen wrote: >>> Don't assume that only the driver would be accessing LNKCTL. ASPM >>> policy changes can trigger write to LNKCTL outside of driver's control. >>> >>> Use pcie_lnkctl_clear_and_set() which does proper locking to avoid >>> losing concurrent updates to the register value. >> >> Wouldn't it be more appropriate to add proper locking to the >> underlying pcie_capability_clear_and_set_word()? > > PCI config space accessors such as this one are also used in hot paths > (e.g. interrupt handlers). They should be kept lean (and lockless) I *think* in case the system uses threaded interrupts you may need locking also in interrupt handlers. > by default. We only need locking for specific PCIe Extended Capabilities > which are concurrently accessed by PCI core code and drivers. > > Thanks, > > Lukas