[ Upstream commit bc4722c359 ]
For sama7g5 and sama7d65 backup mode, we encountered a "ZQ calibrate error"
during recalibrating the impedance in BootStrap.
We found that the impedance value saved in at91_suspend_finish() before
the DDR entered self-refresh mode did not match the resistor values. The
ZDATA field in the DDR3PHY_ZQ0CR0 register uses a modified gray code to
select the different impedance setting.
But these gray code are incorrect, a workaournd from design team fixed the
bug in the calibration logic. The ZDATA contains four independent impedance
elements, but the algorithm combined the four elements into one. The elements
were fixed using properly shifted offsets.
Signed-off-by: Li Bin <bin.li@microchip.com>
[nicolas.ferre@microchip.com: fix indentation and combine 2 patches]
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Tested-by: Ryan Wanner <Ryan.Wanner@microchip.com>
Tested-by: Durai Manickam KR <durai.manickamkr@microchip.com>
Tested-by: Andrei Simion <andrei.simion@microchip.com>
Signed-off-by: Ryan Wanner <Ryan.Wanner@microchip.com>
Link: https://lore.kernel.org/r/28b33f9bcd0ca60ceba032969fe054d38f2b9577.1740671156.git.Ryan.Wanner@microchip.com
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Signed-off-by: Sasha Levin <sashal@kernel.org>
89800836bf