diff options
| author | William Wu <william.wu@rock-chips.com> | 2018-05-16 20:04:44 +0800 |
|---|---|---|
| committer | Tao Huang <huangtao@rock-chips.com> | 2018-05-17 09:59:13 +0800 |
| commit | f8fb8bcd21ec9d26cc5ead78adaf4056317100c7 (patch) | |
| tree | 63075eecf0b2fccd635c014f3c744665b5090e48 /Documentation/kernel-parameters.txt | |
| parent | 44b30beec8cd083369704c30d72178324653ea03 (diff) | |
BACKPORT: phy: rockchip-usb: add handler for usb-uart functionality
Most newer Rockchip SoCs provide the possibility to use a usb-phy
as passthrough for the debug uart (uart2), making it possible to
for example get console output without needing to open the device.
This patch adds an early_initcall to enable this functionality
conditionally via the commandline and also disables the corresponding
usb controller in the devicetree.
Currently only data for the rk3288 is provided, but at least the
rk3188 and arm64 rk3368 also provide this functionality and will be
enabled later.
On a spliced usb cable the signals are tx on white wire(D+) and
rx on green wire(D-).
The one caveat is that currently the reconfiguration of the phy
happens as early_initcall, as the code depends on the unflattened
devicetree being available. Everything is fine if only a regular
console is active as the console-replay will happen after the
reconfiguation. But with earlycon active output up to smp-init
currently will get lost.
The phy is an optional property for the connected dwc2 controller,
so we still provide the phy device but fail all phy-ops with -EBUSY
to make sure the dwc2 does not try to transmit anything on the
repurposed phy.
Change-Id: Ia9eed5b2b83d88fbeb7aabced689b21f4ea0ca69
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: William Wu <william.wu@rock-chips.com>
(cherry picked from commit 605df8af33a7b206611a7bda01384b2b46d80e17)
Diffstat (limited to 'Documentation/kernel-parameters.txt')
| -rw-r--r-- | Documentation/kernel-parameters.txt | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index a5958499e5c9..8693db1dc730 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3502,6 +3502,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. ro [KNL] Mount root device read-only on boot + rockchip.usb_uart + Enable the uart passthrough on the designated usb port + on Rockchip SoCs. When active, the signals of the + debug-uart get routed to the D+ and D- pins of the usb + port and the regular usb controller gets disabled. + rodata= [KNL] on Mark read-only kernel memory as read-only (default). off Leave read-only kernel memory writable for debugging. |