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Thu, 7 May 2020 18:13:57 +0000 From: "Daniel Walker (danielwa)" To: Pratyush Yadav CC: Tudor Ambarus , Vignesh Raghavendra , Richard Weinberger , "xe-linux-external(mailer list)" , "linux-kernel@vger.kernel.org" , "linux-mtd@lists.infradead.org" , "Miquel Raynal" Subject: Re: [RFC-PATCH] mtd: spi-nor: add conditional 4B opcodes Thread-Topic: [RFC-PATCH] mtd: spi-nor: add conditional 4B opcodes Thread-Index: AQHWJJtGYFQgheIq+0WUH0ne4iHf/w== Date: Thu, 7 May 2020 18:13:57 +0000 Message-ID: <20200507181356.GZ9016@zorba> References: <20200507162047.30788-1-danielwa@cisco.com> <20200507180346.gwni4hf6kb6gd2e5@yadavpratyush.com> In-Reply-To: <20200507180346.gwni4hf6kb6gd2e5@yadavpratyush.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-Auto-Response-Suppress: DR, OOF, AutoReply X-MS-TNEF-Correlator: user-agent: Mutt/1.9.4 (2018-02-28) authentication-results: yadavpratyush.com; dkim=none (message not signed) header.d=none;yadavpratyush.com; dmarc=none action=none header.from=cisco.com; 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x-ms-exchange-antispam-messagedata: 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 Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 0371217d-c7b8-4349-ccb6-08d7f2b26931 X-MS-Exchange-CrossTenant-originalarrivaltime: 07 May 2020 18:13:57.8027 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 5ae1af62-9505-4097-a69a-c1553ef7840e X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: mQTeL6dO+6LPABct66ZotViBJ+ncE+Vue2Y2A2hpLnld6gBI/US2zgVrXhauHGdxVxfrS5kPpSOfijPcpizLdA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR11MB2982 X-OriginatorOrg: cisco.com X-Outbound-SMTP-Client: 173.37.102.12, xch-rcd-002.cisco.com X-Outbound-Node: rcdn-core-3.cisco.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 07, 2020 at 11:33:46PM +0530, Pratyush Yadav wrote: > On 07/05/20 09:20AM, Daniel Walker wrote: > > Some chips have 4B opcodes, but there is no way to know if they have > > them. This device tree option allows platform owners to force enable 4b > > opcodes when they know their chips support it even when it can be > > automatically identified. >=20 > Do you mean that two chips might have the same ID but one of them can=20 > support 4B opcodes and the other can not? Is it possible to detect this=20 > in a fixup hook? I think it would be better to do something like this in= =20 > a fixup hook instead of via device tree. =20 Yes. The chip I added the option for is an example of this, it's n25q256a. = I'm not familiar with the fixup hook mechanism, but I would assume you need some way to tell between = the 4B opcode chips and the non-4B opcode chips. For n25q256a, we have not found a= way to do that. Daniel=