Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
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 <krzysztof.kozlowski@linaro.org>,
        "Guntupalli, Manikanta" <manikanta.guntupalli@amd.com>,
        Rob Herring <robh@kernel.org>
Cc:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "krzysztof.kozlowski+dt@linaro.org" 
        <krzysztof.kozlowski+dt@linaro.org>,
        "michal.simek@xilinx.com" <michal.simek@xilinx.com>,
        "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "jirislaby@kernel.org" <jirislaby@kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "git (AMD-Xilinx)" <git@amd.com>,
        "Pandey, Radhey Shyam" <radhey.shyam.pandey@amd.com>,
        "Datta, Shubhrajyoti" <shubhrajyoti.datta@amd.com>,
        "Goud, Srinivas" <srinivas.goud@amd.com>,
        "manion05gk@gmail.com" <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>
 <DM4PR12MB6109C2BCDFD616AE37E10B9A8C6F9@DM4PR12MB6109.namprd12.prod.outlook.com>
 <59b9214a-19e6-fd4e-6982-6e8c28c7e4a8@linaro.org>
From:   Michal Simek <michal.simek@amd.com>
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; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?bVlnTzdHTGtlNm1ETy93OWlVa3VHUitMV1gwWVlVc09OYkJJWE5nQXdHQ3dn?=
 =?utf-8?B?MHdZUmxmRTU5U093bC9ycFhYOTFBeU5UdlhPSFRIM1QyRy8rTTJ2dFN6eEVU?=
 =?utf-8?B?MzV5UnJTQjkzTjd2YXFzcnNFSWdVU0E3MDFJNUo4NW5SUmJBSGY2NldUcFNS?=
 =?utf-8?B?QW41azhQT3UxcjJDNmMwTFpIR3pBODNJZFNyd3EyajRwaXRBMEZSY1VnYjB5?=
 =?utf-8?B?bkwyQ2JabFpOS2tDMjd2aElhL2xuc2Uvbnlla21LanZNSGtseTBaSzBiV1Z5?=
 =?utf-8?B?ZEkyNUsxMVVhSlM2TitOQVhxYnRIS1laVkFsV2g5QWFPazlpZkJQSXh2aHhS?=
 =?utf-8?B?OUxBcmhDT3oraGZ3SmR2UVlPNXNqYjZmWEYxRDFLOURvTzRUbWhPcE03a3cy?=
 =?utf-8?B?RmlFd0swczFPcHpZSTRLNm41NWlxbWZUaG54ckswZFBCSnJEUENjL2l1QzZJ?=
 =?utf-8?B?WCt0a2FMaEplbXNSQUtMektMbzhoaTljU1RFMlJhTUJXR3F2YWcxbTBQNEZF?=
 =?utf-8?B?aUJBWmZCeTdtTGxxRVpPY2VscGF6Mnl1VmNHODlkQmNHSzRwQW5lbDVuUG5D?=
 =?utf-8?B?ODlyVllocXJhSUVaMCt0SG1KL216QjVGb1l0T1oyMVAvbVZMay92Rk1lb0hi?=
 =?utf-8?B?dlNLK3c4Mm1IZUIzNzFNUG1POGZQN2x2WTNoUzk5WnlHcHFPZzVQSFJMRVBo?=
 =?utf-8?B?L2FFOTdUUm9ZQUx1R09ocXEvYUR4RkxKb254SzRXK1E1M04rMkNnaUlhU2tq?=
 =?utf-8?B?elZVTUlZeEVZS0RyTUdDNmV2WXVxODFYQTNGcGN0c1djSWhwc1J5cW9oWFNj?=
 =?utf-8?B?WHlpMUFqd2YwZDluT0RETDdVazZMSEhhSmMxTFJoRFF6RGlpNmNtSGpiLzhG?=
 =?utf-8?B?U3M1VUxRNElPS0Exem5CVkRSNGRNUXg3SnhhMXdzQlNHY3JrdHBDNVE0dGNL?=
 =?utf-8?B?aEhqc21RUXBQaHFBbHdWYmovU0dxUXg5cVhNS1EyLzJrK0M0Y2hleGoyQWRo?=
 =?utf-8?B?LzkvdzhhdFdQZHVzeERWa2tSVmlvSDFZbCtod0M1VFhGV2VaNTlkOTQ0VDZJ?=
 =?utf-8?B?Z09Sbllhc0RhUmRUUTA1Z1FMZjJEZ1hyaEEzRmxITXdvTyt4ZXlHeHJRelZE?=
 =?utf-8?B?aVdDV0ZBTmtPT2pBNFRxL09GSVBNOFNRck1kbnJTeUhrQytiSE5NVlJCeWNJ?=
 =?utf-8?B?ampYR1lqZFh0TXJzQytZM1UwZzFkNlhESEZhVzBnQ2gvU1BnS1l5VGdpd0JP?=
 =?utf-8?B?elRnOCt6Y3NERi9xYVh5RVNJYkl6ODZDek5GM3MwRkJreWFXY1FWMEZpNXgx?=
 =?utf-8?B?R1RCN0hlNmtDMEY0eEQ5bUt4UkIxVDhqYS83eDFkYXNLV242SUFOU0dTeko4?=
 =?utf-8?B?TjlPWWxqcWZzeVpxL0VuczJsQy96d2VQaE8wbUpCbjBvdUpnVmw1WFIxNEs3?=
 =?utf-8?B?WFc4K0JWLzlVSUU0MHd1WjdrU1BLbkw1VmRqV01PTEpOTDk4V3B4aEZjYXdj?=
 =?utf-8?B?MzFjd2lFNjR0cHd0QXRXVW1kVVZWd3lZa05nTDFXTzR3Y1NneG4vZjNabWVI?=
 =?utf-8?B?eDZ4cy8wTkJSdEFXNGhwb05VNkxEQUJWbFZQU3cydVYrOUdXU2JkdUZxS25w?=
 =?utf-8?B?ZElNdkh0akJmYUEzek45TnE1UGV3Yk9ieWNqOFUwZHpmU3N3MVFGOHpibkFt?=
 =?utf-8?B?Qkw4bis4MHFDbVo3ZTdYUU1SQ0ZHekx0ZmR1aDk0WEJlVkc3ZlN0QW1oWlRU?=
 =?utf-8?B?Rld1WFQxb3ZrN2dGYlFPLzF4NDEvUWZhWEZtY3FJYUliNEdEa0lTTnFPbURj?=
 =?utf-8?B?ZExpdmQyNDQ1UmNtdmNVZFp2ZGdCbURIaHZWcnNrR29vNWRNb2wzT2t1dUo5?=
 =?utf-8?B?bmV2enVFR0tZd24zSnYzbGRiaFZ6NFFoSHdHYUludXlsK1puaGMrZkI3Yjkz?=
 =?utf-8?B?U0RqUUM2ZWcvQThISkhNOEpHUEZBMXpyczZNdFBtbXJYN3VrdUhUUEFXSmNK?=
 =?utf-8?B?QXAvSGNKYVl3czJSUmJUSHU0QWQ3WmNGUmZkcnBhUlJkNGcxdVpDbGRneTg5?=
 =?utf-8?B?WGcvQ3lRb2I1cDl0TkpMN2dFVDRxaXdydFI1SmdNVGdiQXgvUWw3UENRZ3RO?=
 =?utf-8?Q?7c0hgPPtwwjDEWvacVZCkG1R3?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 2e88966d-0013-4538-63cd-08db4afc0b99
X-MS-Exchange-CrossTenant-AuthSource: BYAPR12MB4758.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 May 2023 10:57:39.2507
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: FosNAA6Fc2xck4isxjU3Xy8pr9KYf0Xsgv/t/iztY4dgqhoFwoo9Bq/Mh23bMRb6
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW3PR12MB4570
X-Spam-Status: No, score=-2.5 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,NICE_REPLY_A,
        RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE,
        T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On 5/2/23 12:19, Krzysztof Kozlowski wrote:
> On 02/05/2023 12:14, Guntupalli, Manikanta wrote:
>> Hi Rob Herring,
>>
>>> -----Original Message-----
>>> From: Rob Herring <robh@kernel.org>
>>> Sent: Thursday, April 27, 2023 10:14 PM
>>> To: Guntupalli, Manikanta <manikanta.guntupalli@amd.com>
>>> 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; Simek, Michal
>>> <michal.simek@amd.com>; git (AMD-Xilinx) <git@amd.com>; Pandey,
>>> Radhey Shyam <radhey.shyam.pandey@amd.com>; Datta, Shubhrajyoti
>>> <shubhrajyoti.datta@amd.com>; Goud, Srinivas <srinivas.goud@amd.com>;
>>> 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