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Thu, 26 Nov 2020 07:23:48 +0000 From: Damien Le Moal To: Sean Anderson , Serge Semin CC: Mark Brown , "linux-spi@vger.kernel.org" , Rob Herring , "devicetree@vger.kernel.org" Subject: Re: [PATCH 1/3] spi: dw: Add support for 32-bits max xfer size Thread-Topic: [PATCH 1/3] spi: dw: Add support for 32-bits max xfer size Thread-Index: AQHWvmvw8As+5km3TUebXVhjeYQ6BQ== Date: Thu, 26 Nov 2020 07:23:48 +0000 Message-ID: References: <20201119120253.390883-1-damien.lemoal@wdc.com> <20201119120253.390883-2-damien.lemoal@wdc.com> <20201125195221.3pnqipxej3ta7rlc@mobilestation> <82628758-d7a0-299c-51d1-4960dcea2809@gmail.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: gmail.com; dkim=none (message not signed) header.d=none;gmail.com; dmarc=none action=none header.from=wdc.com; x-originating-ip: [2400:2411:43c0:6000:7477:1782:371:aeb9] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: b00b3777-ce19-484b-21b3-08d891dc3778 x-ms-traffictypediagnostic: CH2PR04MB7077: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:10000; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: CH2PR04MB6522.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: b00b3777-ce19-484b-21b3-08d891dc3778 X-MS-Exchange-CrossTenant-originalarrivaltime: 26 Nov 2020 07:23:48.1352 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: L91vKxBdaAI0YqpBDrJnsLLuX6subF/UCkjrvLUcGoCcuQXy2BszeJM/YZJdjLk192CIMinWz8jubu+uRWIYqA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR04MB7077 Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org On 2020/11/26 13:55, Sean Anderson wrote:=0A= > On 11/25/20 2:52 PM, Serge Semin wrote:=0A= [...]=0A= >>> + if (!(dws->caps & DW_SPI_CAP_DWC_SSI)) {=0A= >>> + u32 cr0;=0A= >>> +=0A= >>> + /*=0A= >>> + * Detect APB SSI CTRLR0 size by looking at the data=0A= >>> + * frame size field.=0A= >>> + */=0A= >>=0A= >>> + dw_writel(dws, DW_SPI_CTRLR0, 0xffffffff);=0A= >>=0A= >> This isn't going to work because you need to disable the SSI controller= =0A= >> first. Then please revert the change or cleanup the register and disable= =0A= >> the controller back after finishing the detection.=0A= > =0A= > In U-Boot at least, ctrlr0 is written before every transfer, so there is= =0A= > no need to restore it afterward. Same for enr. I don't know whether this= =0A= > holds true for Linux.=0A= =0A= Same in Linux too. The base value for cr0 is prepared and saved in chip->cr= 0=0A= field when the controller is scanned/reset and that saved base value is use= d for=0A= updating cr0 on every transfer. Serge point here was to have the DFS32 dete= ction=0A= not result in the initial cr0 value changing, as some older versions of the= DW=0A= controller may react to it. The cr0 save/restore in the detection does not= =0A= matter for the K210 though. Since this is only done on scan/reset and not i= n the=0A= fast path, I think it is OK and definitely safer.=0A= =0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=