Re: [RFC PATCH 0/6] spi: Add OSPI PHY calibration support for spi-cadence-quadspi

[Pratyush Yadav <p.yadav@xxxxxx>]

On 12/03/21 11:20AM, Michael Walle wrote:
> Am 2021-03-12 11:10, schrieb Pratyush Yadav:
> > There is usually a delay from when the flash drives the data line (IOW,
> > puts a data bit on it) and when the signal reaches the controller. This
> > delay can vary by the flash, board, silicon characteristics,
> > temperature, etc.
> 
> Temperature might change over time, but the calibration is only done
> once. I don't know how much influence the temperature actually has, but
> our boards are usually operating from -40°C to +85°C. So there might be
> a possible temperature difference of 125K between actual calibration and
> when the flash is accessed.

The algorithm supports a temperature range of -45 C to +130 C. The 
temperature is checked at calibration time and adjustments are made to 
make sure the reads work over the entire temperature range [0].

[0] The current implementation does not have a way to query the 
temperature from the sensor (see cqspi_get_temp()), so it always assumes 
the temperature at calibration time is 45 C. But that can be added later 
once the temperature sensor driver is implemented.

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.