| b725dc45 | 03-Aug-2015 |
Simon Glass <sjg@chromium.org> |
i2c: Add a mux for GPIO-based I2C bus arbitration
While I2C supports multi-master buses this is difficult to get right.
The implementation on the master side in software is quite complex.
Clock-stre
i2c: Add a mux for GPIO-based I2C bus arbitration
While I2C supports multi-master buses this is difficult to get right.
The implementation on the master side in software is quite complex.
Clock-stretching and the arbitrary time that an I2C transaction can take
make it difficult to share the bus fairly in the face of high traffic.
When one or more masters can be reset independently part-way through a
transaction it is hard to know the state of the bus.
This driver provides a scheme based on two 'claim' GPIOs, one driven by the
AP (Application Processor, meaning the main CPU) and one driven by the EC
(Embedded Controller, a small CPU aimed at handling system tasks). With
these they can communicate and reliably share the bus. This scheme has
minimal overhead and involves very little code. It is used on snow to
permit the EC and the AP to share access to the main system PMIC and
battery. The scheme can survive reboots by either side without difficulty.
This scheme has been tested in the field with millions of devices.
Since U-Boot runs on the AP, the terminology used is 'our' claim GPIO,
meaning the AP's, and 'their' claim GPIO, meaning the EC's. This terminology
is used by the device tree bindings in Linux also.
Signed-off-by: Simon Glass <sjg@chromium.org>
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| 7bea5271 | 27-Jul-2015 |
Simon Glass <sjg@chromium.org> |
x86: Update README to explain booting Ubuntu on Minnowmax
The steps required to boot a Linux distribution from U-Boot on x86 are not
very complicated, but it is a good idea to have these written dow
x86: Update README to explain booting Ubuntu on Minnowmax
The steps required to boot a Linux distribution from U-Boot on x86 are not
very complicated, but it is a good idea to have these written down in an
accessible place.
Document how to examine the boot media from U-Boot, how to load a kernel,
load a ramdisk, set the kernel boot arguments and start the kernel. With
these instructions Ubuntu boots mostly normally on Minnowmax.
Note that the TSC timer does not operate correctly and gives warnings in
the boot log. I expect that ACPI support will solve this.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
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| 17da3c0c | 12-Jun-2015 |
Paul Kocialkowski <contact@paulk.fr> |
usb: Fastboot function config for better consistency with other functions
USB download gadget functions such as thor and dfu have a separate config option
for the USB gadget part of the code, indepe
usb: Fastboot function config for better consistency with other functions
USB download gadget functions such as thor and dfu have a separate config option
for the USB gadget part of the code, independent from the command part.
This switches the fastboot USB gadget to the same scheme, for better
consistency.
Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>
Test HW: Odroid_XU3 (Exynos5422), trats (Exynos4210)
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