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Received: from BYAPR12MB4758.namprd12.prod.outlook.com (2603:10b6:a03:a5::28) by MW3PR12MB4570.namprd12.prod.outlook.com (2603:10b6:303:5f::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6340.31; Tue, 2 May 2023 10:57:40 +0000 Received: from BYAPR12MB4758.namprd12.prod.outlook.com ([fe80::20b9:d472:1981:cf94]) by BYAPR12MB4758.namprd12.prod.outlook.com ([fe80::20b9:d472:1981:cf94%4]) with mapi id 15.20.6340.031; Tue, 2 May 2023 10:57:40 +0000 Message-ID: <39d3e076-94ad-a349-5df6-b6e78714e407@amd.com> Date: Tue, 2 May 2023 12:57:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Content-Language: en-US To: Krzysztof Kozlowski , "Guntupalli, Manikanta" , Rob Herring Cc: "gregkh@linuxfoundation.org" , "krzysztof.kozlowski+dt@linaro.org" , "michal.simek@xilinx.com" , "linux-serial@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "jirislaby@kernel.org" , "linux-arm-kernel@lists.infradead.org" , "git (AMD-Xilinx)" , "Pandey, Radhey Shyam" , "Datta, Shubhrajyoti" , "Goud, Srinivas" , "manion05gk@gmail.com" References: <1682512187-8828-1-git-send-email-manikanta.guntupalli@amd.com> <1682512187-8828-2-git-send-email-manikanta.guntupalli@amd.com> <20230427164351.GA3146210-robh@kernel.org> <59b9214a-19e6-fd4e-6982-6e8c28c7e4a8@linaro.org> From: Michal Simek Subject: Re: [PATCH 1/2] dt-bindings: Add optional gpio property to uartps node to support rs485 In-Reply-To: <59b9214a-19e6-fd4e-6982-6e8c28c7e4a8@linaro.org> Content-Type: text/plain; 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krzysztof.kozlowski+dt@linaro.org; >>> michal.simek@xilinx.com; linux-serial@vger.kernel.org; >>> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; >>> jirislaby@kernel.org; linux-arm-kernel@lists.infradead.org; Simek, Michal >>> ; git (AMD-Xilinx) ; Pandey, >>> Radhey Shyam ; Datta, Shubhrajyoti >>> ; Goud, Srinivas ; >>> manion05gk@gmail.com >>> Subject: Re: [PATCH 1/2] dt-bindings: Add optional gpio property to uartps >>> node to support rs485 >>> >>> On Wed, Apr 26, 2023 at 05:59:46PM +0530, Manikanta Guntupalli wrote: >>>> Add optional gpio property to uartps node and add reference to rs485.yaml >>> >>> The diff tells me that already. Why? >> Please check Figure 11-3 (Page number 37) in the below mentioned data sheet, It shows PMOD (ISOW14x2) devices used in half duplex configuration. Driver outputs Y and Z are shorted to A and B respectively. This reduces overall cabling requirements. Also DE/RE are shorted to each other, and at a time, any node acts as either a driver or a receiver. >> Using above optional GPIO controlling driver or a receiver. This GPIO is optional because it is not required for uart console node. >> >> Here, >> DE - Driver enable. If pin is floating, driver is disabled (internal pull-down resistor) >> RE - Receiver enable. If pin is floating, receiver buffer is disabled (internal pull-up resistor) >> >> Datasheet: >> https://www.ti.com/lit/ds/symlink/isow1432.pdf?ts=1682607122706&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FISOW1432%252Fpart-details%252FISOW1432DFMR%253FkeyMatch%253DISOW1432DFMR%2526tisearch%253Dsearch-everything%2526usecase%253DOPN > > Your request for us to get into some datasheet somewhere, to get the > answer to the basic question, is not reasonable. Commit must justify its > existence, not some external source. Not really. Manual itself just shows picture of that connection if you are interested. On schematics it looks like that DE and /RE are just handle via one gpio. That's why you need 3 wires instead of 4. Definitely it should be described better. My concern was more about choosing proper name for this functionality. Thanks, Michal