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[94.175.9.129]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435b1f7c9cesm14772613f8f.41.2026.01.24.04.36.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 24 Jan 2026 04:36:42 -0800 (PST) Date: Sat, 24 Jan 2026 12:36:42 +0000 From: Stafford Horne To: Gary Lau Cc: linusw , linux-kernel , linux-openrisc , devicetree , robh , krzk+dt , conor+dt , geert+renesas , "krzysztof.kozlowski" , brgl , linux-gpio Subject: Re: [PATCH v6 1/6] dt-bindings: gpio-mmio: Correct opencores GPIO Message-ID: References: Precedence: bulk X-Mailing-List: linux-openrisc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Jan 23, 2026 at 10:18:04PM +0800, Gary Lau wrote: > Hi Stafford, > > I should clarify my setup: I'm using hardware address translation to make the > OpenCores 8-bit GPIO appear as 32-bit to the CPU. Specifically: > > 1. Address translation: The CPU's 32-bit addresses are right-shifted by 2 bits >    (adr_i[2] in Verilog), so each 32-bit CPU access maps to the correct 8-bit >    OpenCores register. > > 2. Data width adaptation: Only dat_i[7:0] and dat_o[7:0] are connected, so >    32-bit writes are truncated to 8-bit, and reads are zero-extended. > > This hardware wrapper makes brcm,bcm6345-gpio driver "work" with my OpenCores > GPIO, but it's really a hardware-level compatibility layer, not true software > compatibility. > > So you're absolutely right that the native opencores,gpio isn't compatible > with brcm,bcm6345-gpio. My setup works because of custom hardware translation, > not because the IP cores are compatible. Thanks Gary for testing. -Stafford