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Mon, 24 May 2021 02:53:36 +0000 Received: from PH0PR11MB5191.namprd11.prod.outlook.com ([fe80::ac4d:5dd3:c365:cd49]) by PH0PR11MB5191.namprd11.prod.outlook.com ([fe80::ac4d:5dd3:c365:cd49%9]) with mapi id 15.20.4150.027; Mon, 24 May 2021 02:53:36 +0000 From: "Li, Meng" To: =?iso-8859-1?Q?Uwe_Kleine-K=F6nig?= CC: "lars@metafoo.de" , "Michael.Hennerich@analog.com" , "jic23@kernel.org" , "pmeerw@pmeerw.net" , "linux-kernel@vger.kernel.org" , "linux-iio@vger.kernel.org" Subject: RE: [PATCH] driver: adc: ltc2497: return directly after reading the adc conversion value Thread-Topic: [PATCH] driver: adc: ltc2497: return directly after reading the adc conversion value Thread-Index: AQHXRutZA2KT9UoVoUu9pd++4IrNe6rqkr4AgAdvZIA= Date: Mon, 24 May 2021 02:53:36 +0000 Message-ID: References: <20210512045725.23390-1-Meng.Li@windriver.com> <20210519092104.pntanimcjg6s6fca@pengutronix.de> In-Reply-To: <20210519092104.pntanimcjg6s6fca@pengutronix.de> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: pengutronix.de; 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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: windriver.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: PH0PR11MB5191.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: aa937384-2de8-47f5-33d0-08d91e5f204b X-MS-Exchange-CrossTenant-originalarrivaltime: 24 May 2021 02:53:36.1126 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ddb2873-a1ad-4a18-ae4e-4644631433be X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: RbaU10q7UxWxlzJ6pTYOWI3dFo0VgOC6R+3iHQtn125dWQLkbVu0aGzR5c1n9cYtxFa86Vps8/kL4xaXzRmIBw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR11MB5077 X-Proofpoint-GUID: N_arIoVxqCY9TmjnUb2At67bpLT12sw3 X-Proofpoint-ORIG-GUID: N_arIoVxqCY9TmjnUb2At67bpLT12sw3 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-05-24_02:2021-05-20,2021-05-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 impostorscore=0 suspectscore=0 adultscore=0 phishscore=0 clxscore=1015 mlxlogscore=999 bulkscore=0 spamscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105240019 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Uwe Kleine-K=F6nig > Sent: Wednesday, May 19, 2021 5:21 PM > To: Li, Meng > Cc: lars@metafoo.de; Michael.Hennerich@analog.com; jic23@kernel.org; > pmeerw@pmeerw.net; linux-kernel@vger.kernel.org; linux- > iio@vger.kernel.org > Subject: Re: [PATCH] driver: adc: ltc2497: return directly after reading = the adc > conversion value >=20 > On Wed, May 12, 2021 at 12:57:25PM +0800, Meng.Li@windriver.com wrote: > > From: Meng Li > > > > When read adc conversion value with below command: > > cat /sys/.../iio:device0/in_voltage0-voltage1_raw > > There is an error reported as below: > > ltc2497 0-0014: i2c transfer failed: -EREMOTEIO This i2c transfer > > issue is introduced by commit 69548b7c2c4f ("iio: > > adc: ltc2497: split protocol independent part in a separate module"). > > When extract the common code into ltc2497-core.c, it change the code > > logic of function ltc2497core_read(). With wrong reading sequence, the > > action of enable adc channel is sent to chip again during adc channel > > is in conversion status. In this way, there is no ack from chip, and > > then cause i2c transfer failed. > > In order to keep the code logic is the same with original ideal, it is > > need to return direct after reading the adc conversion value. > > > > Fixes: 69548b7c2c4f ("iio: adc: ltc2497: split protocol independent > > part in a separate module ") > > Cc: stable@vger.kernel.org > > Signed-off-by: Meng Li > > --- > > drivers/iio/adc/ltc2497.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c > > index 1adddf5a88a9..fd5a66860a47 100644 > > --- a/drivers/iio/adc/ltc2497.c > > +++ b/drivers/iio/adc/ltc2497.c > > @@ -41,6 +41,8 @@ static int ltc2497_result_and_measure(struct > ltc2497core_driverdata *ddata, > > } > > > > *val =3D (be32_to_cpu(st->buf) >> 14) - (1 << 17); > > + > > + return ret; >=20 > This looks wrong for me. The idea of the function > ltc2497_result_and_measure is that it reads the result and starts a new > measurement. I guess the problem is that ltc2497_result_and_measure is > called to early, not that it does too much. >=20 > But note I don't have such a system handy to actually debug this any more= . >=20 Hi Uwe, Thanks for your comments. I would like to verify your ideal if you can offer your patch or tell me wh= ere to change code. Thanks, Limeng > Best regards > Uwe >=20 > -- > Pengutronix e.K. | Uwe Kleine-K=F6nig = | > Industrial Linux Solutions | https://www.pengutronix.de/ = |