On 2/7/23 06:09, Sai Krishna Potthuri wrote:
Enable PHY and DQS required for Xilinx Versal Octal SPI to operate in DTR protocol. Add and update device_id field in spi_mem structure with flash id information. Xilinx Versal Octal SPI driver requires the device id information to perform the Rx tuning operation. Since there is no common Tuning Data Pattern defined across all vendors, controllers like Xilinx Versal Octal SPI which requires Rx tuning to find out the optimal sampling point for data lines, this device id information will be used as a golden data.
Using only 6 bytes as golden pattern seems fragile, but you are aware of that, as I see that you chose to read the ID 10 times to make the decision whether the tap is valid or not. Other option (which is not perfect) is to use SFDP data as golden pattern. If I remember correctly, JESD216 suggests to use the Read SFDP cmd at 50 MHz, so it won't help you much. In practice SPI NOR uses the Read SFDP command at the flash's maximum speed and we haven't seen problems. But better would be to use some flash OTP data maybe? I remember Pratyush has submitted a phy calibration series in the past, I haven't had the chance to read his proposal. Did you? How's your proposal different than his? Cheers, ta
The reason behind choosing this approach instead of reading the ID again in the controller driver is to make it generic solution. - Other controller drivers which want to use similar tuning process, they will make use of this ID instead of reading the ID again in the driver. - Also, we can avoid hardcoding the command information and initiating the transfer in the controller driver as this should happen from spi-nor. Sai Krishna Potthuri (3): spi: cadence-quadspi: Add support for PHY module and DQS mtd: spi-nor: Add and update device_id field in spi_mem structure spi: cadence-quadspi: Add Rx tuning support for Xilinx Versal OSPI drivers/mtd/spi-nor/core.c | 1 + drivers/spi/spi-cadence-quadspi.c | 226 +++++++++++++++++++++++++++++- include/linux/spi/spi-mem.h | 4 + 3 files changed, 230 insertions(+), 1 deletion(-)
