da6c2addf6
To set the mux mode of a pin two bits must be set. Up to now this is
implemented using the following idiom:
writel(mask, reg + CLR);
writel(value, reg + SET);
. This however results in the mux mode being 0 between the two writes.
On my machine there is an IC's reset pin connected to LCD_D20. The
bootloader configures this pin as GPIO output-high (i.e. not holding the
IC in reset). When Linux reconfigures the pin to GPIO the short time
LCD_D20 is muxed as LCD_D20 instead of GPIO_1_20 is enough to confuse
the connected IC.
The same problem is present for the pin's drive strength setting which is
reset to low drive strength before using the right value.
So instead of relying on the hardware to modify the register setting
using two writes implement the bit toggling using read-modify-write.
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.