On Thu, Dec 10, 2020 at 06:06:59PM +0800, John Wang wrote: > On Thu, Dec 10, 2020 at 5:42 PM Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Thu, Dec 10, 2020 at 05:28:53PM +0800, John Wang wrote: > > > From: Oskar Senft <osk@xxxxxxxxxx> > > > > > > This driver adds sysfs files that allow the BMC userspace to configure > > > how UARTs and physical serial I/O ports are routed. > > > > > > Tested: Checked correct behavior (both read & write) on TYAN S7106 > > > board by manually changing routing settings and confirming that bits > > > flow as expected. Tested for UART1 and UART3 as this board doesn't have > > > the other UARTs wired up in a testable way. > > > > > > Signed-off-by: Oskar Senft <osk@xxxxxxxxxx> > > > Signed-off-by: Yong Li <yong.b.li@xxxxxxxxxxxxxxx> > > > Signed-off-by: Vernon Mauery <vernon.mauery@xxxxxxxxxxxxxxx> > > > Signed-off-by: John Wang <wangzhiqiang.bj@xxxxxxxxxxxxx> > > > --- > > > .../stable/sysfs-driver-aspeed-uart-routing | 14 + > > > .../misc-devices/aspeed-uart-routing.txt | 49 +++ > > > drivers/misc/Kconfig | 6 + > > > drivers/misc/Makefile | 1 + > > > drivers/misc/aspeed-uart-routing.c | 383 ++++++++++++++++++ > > > 5 files changed, 453 insertions(+) > > > create mode 100644 Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing > > > create mode 100644 Documentation/misc-devices/aspeed-uart-routing.txt > > > create mode 100644 drivers/misc/aspeed-uart-routing.c > > > > > > diff --git a/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing b/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing > > > new file mode 100644 > > > index 000000000000..5068737d9c12 > > > --- /dev/null > > > +++ b/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing > > > @@ -0,0 +1,14 @@ > > > +What: /sys/bus/platform/drivers/aspeed-uart-routing/*/io* > > > +Date: August 2018 > > > +Contact: Oskar Senft <osk@xxxxxxxxxx> > > > +Description: Configures the input source for the specific physical > > > + serial I/O port. > > > +Users: OpenBMC. Proposed changes should be mailed to > > > + openbmc@xxxxxxxxxxxxxxxx > > > + > > > +What: /sys/bus/platform/drivers/aspeed-uart-routing/*/uart* > > > +Date: August 2018 > > > +Contact: Oskar Senft <osk@xxxxxxxxxx> > > > +Description: Configures the input source for the specific UART. > > > +Users: OpenBMC. Proposed changes should be mailed to > > > + openbmc@xxxxxxxxxxxxxxxx > > > diff --git a/Documentation/misc-devices/aspeed-uart-routing.txt b/Documentation/misc-devices/aspeed-uart-routing.txt > > > new file mode 100644 > > > index 000000000000..cf1c2a466875 > > > --- /dev/null > > > +++ b/Documentation/misc-devices/aspeed-uart-routing.txt > > > @@ -0,0 +1,49 @@ > > > +Kernel driver aspeed-uart-routing > > > +================================= > > > + > > > +Supported chips: > > > +ASPEED AST2500/AST2600 > > > + > > > +Author: > > > +Google LLC > > > + > > > +Description > > > +----------- > > > + > > > +The Aspeed AST2500/AST2600 allows to dynamically route the inputs for the > > > +built-in UARTS and physical serial I/O ports. > > > + > > > +This allows, for example, to connect the output of UART to another UART. > > > +This can be used to enable host<->BMC communication via UARTs, e.g. to allow > > > +access to the host's serial console. > > > + > > > +This driver is for the BMC side. The sysfs files allow the BMC userspace > > > +which owns the system configuration policy, to configure how UARTs and > > > +physical serial I/O ports are routed. > > > + > > > +The driver provides the following files in sysfs: > > > +uart1 Configure the input signal to UART1. > > > +uart2 Configure the input signal to UART2. > > > +uart3 Configure the input signal to UART3. > > > +uart4 Configure the input signal to UART4. > > > +uart5 Configure the input signal to UART5. > > > +io1 Configure the input signal to physical serial port 1. > > > +io2 Configure the input signal to physical serial port 2. > > > +io3 Configure the input signal to physical serial port 3. > > > +io4 Configure the input signal to physical serial port 4. > > > +io5 Configure the input signal to physical serial port 5. > > > + > > > +When read, each file shows the list of available options with the currently > > > +selected option marked by square brackets "[]". The list of available options > > > +depends on the selected file. > > > + > > > +Example: > > > +$ cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1 > > > +[io1] io2 io3 io4 uart2 uart3 uart4 io6 > > > + > > > +In this case, UART1 gets its input signal from IO1 (physical serial port 1). > > > + > > > +$ echo -n "uart3" \ > > > + >/sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1 > > > +$ cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1 > > > +io1 io2 io3 io4 uart2 [uart3] uart4 io6 > > > > Are you sure there are no other ways to configure this type of thing, > > than to a driver-specific sysfs file? > > I think this is good. but what's your suggestion? I do not know, but isn't this normally handled in a dts file? Why must it be done "on the fly" like this? > If I use a driver-specific sysfs and modify the code based on the > comments, is this a good direction to go? That's what you are trying to do here, and is why I am objecting to it :) thanks, greg k-h
