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Tue, 9 Feb 2021 13:18:21 +0000 From: Adam Thomson To: Mark Jonas , Support Opensource , Lee Jones CC: "linux-kernel@vger.kernel.org" , "linux-i2c@vger.kernel.org" , Adam Thomson , Steve Twiss , "marek.vasut@gmail.com" , "tingquan.ruan@cn.bosch.com" , "hubert.streidl@de.bosch.com" , Wolfram Sang Subject: RE: [PATCH v4] mfd: da9063: Support SMBus and I2C mode Thread-Topic: [PATCH v4] mfd: da9063: Support SMBus and I2C mode Thread-Index: AQHW/i8Ewc5FHProsE227gGqlaHq06pPzvYw Date: Tue, 9 Feb 2021 13:18:21 +0000 Message-ID: References: <20210208152758.13093-1-mark.jonas@de.bosch.com> In-Reply-To: <20210208152758.13093-1-mark.jonas@de.bosch.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: de.bosch.com; dkim=none (message not signed) header.d=none;de.bosch.com; dmarc=none action=none header.from=diasemi.com; x-ms-exchange-messagesentrepresentingtype: 1 x-originating-ip: [147.161.166.124] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 8cd281a1-1203-4b45-7421-08d8ccfd2c97 x-ms-traffictypediagnostic: PAXPR10MB4670: x-ms-exchange-sharedmailbox-routingagent-processed: True x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8882; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: diasemi.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: PR3PR10MB4142.EURPRD10.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-Network-Message-Id: 8cd281a1-1203-4b45-7421-08d8ccfd2c97 X-MS-Exchange-CrossTenant-originalarrivaltime: 09 Feb 2021 13:18:21.9073 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 511e3c0e-ee96-486e-a2ec-e272ffa37b7c X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Q2A/6ruvqj4S7vormmjLhX0TLQ+JxeVloCy1FlCeJnDzvUuIZ5jBq18J2bu0ng9PFQH4/7tIahI3eCE9gtL8LHF0uWSA8Rwu/82ayapGiZ4= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PAXPR10MB4670 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08 February 2021 15:28, Mark Jonas wrote: > From: Hubert Streidl >=20 > By default the PMIC DA9063 2-wire interface is SMBus compliant. This > means the PMIC will automatically reset the interface when the clock > signal ceases for more than the SMBus timeout of 35 ms. >=20 > If the I2C driver / device is not capable of creating atomic I2C > transactions, a context change can cause a ceasing of the clock signal. > This can happen if for example a real-time thread is scheduled. Then > the DA9063 in SMBus mode will reset the 2-wire interface. Subsequently > a write message could end up in the wrong register. This could cause > unpredictable system behavior. >=20 > The DA9063 PMIC also supports an I2C compliant mode for the 2-wire > interface. This mode does not reset the interface when the clock > signal ceases. Thus the problem depicted above does not occur. >=20 > This patch tests for the bus functionality "I2C_FUNC_I2C". It can > reasonably be assumed that the bus cannot obey SMBus timings if > this functionality is set. SMBus commands most probably are emulated > in this case which is prone to the latency issue described above. >=20 > This patch enables the I2C bus mode if I2C_FUNC_I2C is set or > otherwise enables the SMBus mode for a native SMBus controller > which doesn't have I2C_FUNC_I2C set. >=20 > Signed-off-by: Hubert Streidl > Signed-off-by: Mark Jonas Thanks for your efforts. Looks sensible to me, so: Reviewed-by: Adam Thomson