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Tue, 4 Mar 2025 03:24:56 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-fpga@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Tue, 04 Mar 2025 09:24:35 +0100 From: "Arnd Bergmann" To: "Richard Cochran" , "Andy Shevchenko" Cc: "Arnd Bergmann" , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , "Andrew Lunn" , "David S . Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Tianfei Zhang" , "Jonathan Lemon" , "Vadim Fedorenko" , "Greg Kroah-Hartman" , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , "Calvin Owens" , "Philipp Stanner" , Netdev , linux-kernel@vger.kernel.org, linux-fpga@vger.kernel.org Message-Id: <7fd3c712-4c31-435c-80c1-1e042c9b5999@app.fastmail.com> In-Reply-To: References: <20250227141749.3767032-1-arnd@kernel.org> Subject: Re: [PATCH] RFC: ptp: add comment about register access race Content-Type: text/plain Content-Transfer-Encoding: 7bit On Tue, Mar 4, 2025, at 05:09, Richard Cochran wrote: > On Mon, Mar 03, 2025 at 09:50:01AM +0200, Andy Shevchenko wrote: >> Perhaps it's still good to have a comment, but rephrase it that the code is >> questionable depending on the HW behaviour that needs to be checked. > > IIRC both ixp4xx and the PCH are the same design and latch high reg on > read of low. Ok, if that's a common thing, let's assume that the drivers are all correct for the respective hardware and discard my patch. With the patch I have queued up in the asm-generic tree, the behavior changes so ioread64_lo_hi() no longer gets turned into a single 64-bit access, and that is then more likely to be correct for both 32-bit and 64-bit architectures in case the device doesn't actually implement 64-bit transactions but does correctly latch the contents. Arnd