On 2017-10-18 04:38, Guenter Roeck wrote: > On 10/17/2017 03:16 PM, Rob Herring wrote: >> On Fri, Oct 13, 2017 at 01:35:27PM -0700, Guenter Roeck wrote: >>> On Fri, Oct 13, 2017 at 04:26:57PM +0200, Peter Rosin wrote: >>>> On 2017-10-13 15:50, Guenter Roeck wrote: >>>>> On 10/13/2017 02:27 AM, Peter Rosin wrote: >>>>>> With a nxp,se97 chip on an atmel sama5d31 board, the I2C adapter driver >>>>>> is not always capable of avoiding the 25-35 ms timeout as specified by >>>>>> the SMBUS protocol. This may cause silent corruption of the last bit of >>>>>> any transfer, e.g. a one is read instead of a zero if the sensor chip >>>>>> times out. This also affects the eeprom half of the nxp-se97 chip, where >>>>>> this silent corruption was originally noticed. Other I2C adapters probably >>>>>> suffer similar issues, e.g. bit-banging comes to mind as risky... >>>>>> >>>>>> The SMBUS register in the nxp chip is not a standard Jedec register, but >>>>>> it is not special to the nxp chips either, at least the atmel chips >>>>>> have the same mechanism. Therefore, do not special case this on the >>>>>> manufacturer, it is opt-in via the device property anyway. >>>>>> >>>>>> Signed-off-by: Peter Rosin <peda@xxxxxxxxxx> >>>>>> --- >>>>>> Documentation/devicetree/bindings/hwmon/jc42.txt | 4 ++++ >>>>>> drivers/hwmon/jc42.c | 20 ++++++++++++++++++++ >>>>>> 2 files changed, 24 insertions(+) >>>>>> >>>>>> diff --git a/Documentation/devicetree/bindings/hwmon/jc42.txt b/Documentation/devicetree/bindings/hwmon/jc42.txt >>>>>> index 07a250498fbb..f569db58f64a 100644 >>>>>> --- a/Documentation/devicetree/bindings/hwmon/jc42.txt >>>>>> +++ b/Documentation/devicetree/bindings/hwmon/jc42.txt >>>>>> @@ -34,6 +34,10 @@ Required properties: >>>>>> >>>>>> - reg: I2C address >>>>>> >>>>>> +Optional properties: >>>>>> +- smbus-timeout-disable: When set, the smbus timeout function will be disabled. >>>>>> + This is not supported on all chips. >> >> Is this only for jc24 devices or could be any smbus device? >> > > SMBus timeout is a standard SMBus functionality, so I would say any. It is by > default enabled on an SMBus device (actually it is not just enabled, it is > mandatory). The ability to disable it comes handy if a SMBus chip is connected > to an I2C controller which does not (or not necessarily) follow SMBus rules. > > I had seen that problem myself with MAX6697, and STTS751 (and its driver) also > supports it. So, is the approach with an optional smbus-timeout-disable property documented in .../bindings/hwmon/jc42.txt good-to-go or should it be documented in some common SMBus client-device file? I don't fine any such beast, so I'm unsure how to proceed in that case. Cheers, Peter -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
