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Sun, 20 Sep 2026 05:35:56 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface MIME-Version: 1.0 X-ThreadId: AzgOxjlYMeWB Date: Sun, 20 Sep 2026 11:35:36 +0200 From: "Arnd Bergmann" To: "Qingfang Deng" Cc: Linux-Arch , "Catalin Marinas" , "Will Deacon" , "Mark Rutland" , "Anshuman Khandual" , "Vikram Sethi" , "Mike Rapoport" , "Shanker Donthineni" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Message-Id: <114d7d69-dd0a-499a-8cd5-732baa21c74c@app.fastmail.com> In-Reply-To: <3250a625-7900-40a9-8f3c-612d333122dc@app.fastmail.com> References: <20260920014357.7069-1-qingfang.deng@linux.dev> <20260920014357.7069-3-qingfang.deng@linux.dev> <5847c824-8d69-4d02-af2f-896bf47f0732@app.fastmail.com> <9895e60c-6a3c-40c8-b188-51891ee6b216@linux.dev> <3250a625-7900-40a9-8f3c-612d333122dc@app.fastmail.com> Subject: Re: [PATCH v2 3/3] arm64: use generic MMIO accessors Content-Type: text/plain Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260920_023603_898702_3090D493 X-CRM114-Status: GOOD ( 10.85 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sun, Sep 20, 2026, at 11:30, Arnd Bergmann wrote: > On Sun, Sep 20, 2026, at 11:24, Qingfang Deng wrote: >> >> Regarding unaligned accesses, the splitting can only happen when the >> address is known to be unaligned at compile-time. Do these accessors >> need to support unaligned MMIO? If so, I could add >> OPTIMIZER_HIDE_VAR(addr) to the generic accessors. > > I think all architectures that have had this problem just started > using the inline asm variant, and I'd probably try to encourage > that more. Also, I have only seen this problem in combination with driver bugs that define their MMIO registers as a __packed data structure instead of the usual 'void __iomem*' with constant offset or a normal structure without packing. Arnd