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[ Upstream commit bc4722c3598d0e2c2dbf9609a3d3198993093e2b ] 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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.