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Sam Edwards
92f095553a
[ Upstream commit37f3d61087] JEDEC standard JESD84-B51 defines the eMMC Data Strobe line, which is currently used only in HS400 mode, as a device->host clock signal that "is used only in read operation. The Data Strobe is always High-Z (not driven by the device and pulled down by RDS) or Driven Low in write operation, except during CRC status response." RDS is a pull-down resistor specified in the 10K-100K ohm range. Thus per the standard, the Data Strobe is always pulled to ground (by the eMMC and/or RDS) during write operations. Evidently, the eMMC host controller in the RK3588 considers an active voltage on the eMMC-DS line during a write to be an error. The default (i.e. hardware reset, and Rockchip BSP) behavior for the RK3588 is to activate the eMMC-DS pin's builtin pull-down. As a result, many RK3588 board designers do not bother adding a dedicated RDS resistor, instead relying on the RK3588's internal bias. The current devicetree, however, disables this bias (`pcfg_pull_none`), breaking HS400-mode writes for boards without a dedicated RDS, but with an eMMC chip that chooses to High-Z (instead of drive-low) the eMMC-DS line. (The Turing RK1 is one such board.) Fix this by changing the bias in the (common) emmc_data_strobe case to reflect the expected hardware/BSP behavior. This is unlikely to cause regressions elsewhere: the pull-down is only relevant for High-Z eMMCs, and if this is redundant with a (dedicated) RDS resistor, the effective result is only a lower resistance to ground -- where the range of tolerance is quite high. If it does, it's better fixed in the specific devicetrees. Fixes:d85f8a5c79("arm64: dts: rockchip: Add rk3588 pinctrl data") Signed-off-by: Sam Edwards <CFSworks@gmail.com> Link: https://lore.kernel.org/r/20231205202900.4617-2-CFSworks@gmail.com Signed-off-by: Heiko Stuebner <heiko@sntech.de> 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.