Stefan, > I cannot answer whether the delay is needed for atomic transfer or not. > But I can give a bit of context for I2C atomic transfers in general. > > These where only introduced for a very narrow and special uses shutting > down the device/power with external PMICs in the kernel's shutdown > handlers. Well, I guess I'm abusing this code a bit. The problem is I use Sony IMX290 and IMX462 image sensors, and they have an apparently hard-coded timeout of about 2^18 their master clock cycles (= ca. 7 ms with my setup). After the timeout they simply disconnect from the I2C bus. Of course, this isn't mentioned in the docs. Unfortunately, "normal" I2C accesses take frequently more than those 7 ms (mostly due to scheduling when all CPU cores are in use). So I hacked the IMX I2C driver a bit and now all accesses to the sensor use the atomic paths and local_irq_save() (inside the driver only). > My understand is that an ordinary I2C device would just use normal (and > sleepable) I2C transfers while the device is in use. You are spot-on here :-) Now I use IMX 290 and 462. OTOH I wonder if such issues are limited to those sensors only. Thanks for your immediate response, -- Krzysztof "Chris" Hałasa Sieć Badawcza Łukasiewicz Przemysłowy Instytut Automatyki i Pomiarów PIAP Al. Jerozolimskie 202, 02-486 Warszawa
