Add a driver for Greybus nodes attached over a plain serial port. The node is registered with the software SVC (gb-softsvc), which handles the SVC protocol on behalf of the AP, so no dedicated coprocessor running SVC firmware is needed.
Greybus messages are carried over HDLC framing on the wire. Each frame carries a one-byte address (0x01 for Greybus) and control byte, followed by the 16-bit CPort ID and the Greybus message itself.
Port parameters are taken from the firmware node: "baudrate" if present, otherwise 115200, with flow control and parity disabled.
Since gb-uart-node imports types from gb-softsvc, Rust to Rust calling setup from nova-core [0] is being used.
[0]: https://lore.kernel.org/all/20260622-nova-exports-v5-0-6191773fc977@nvidia.c...
Signed-off-by: Ayush Singh ayush@beagleboard.org --- MAINTAINERS | 6 ++ drivers/greybus/.gitignore | 1 + drivers/greybus/Kconfig | 15 +++ drivers/greybus/Makefile | 48 +++++++++ drivers/greybus/gb_uart_node.rs | 231 ++++++++++++++++++++++++++++++++++++++++ 5 files changed, 301 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS index 3ba56cdbf056..037a87b74800 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -11334,6 +11334,12 @@ L: greybus-dev@lists.linaro.org (moderated for non-subscribers) S: Maintained F: drivers/greybus/gb_softsvc.rs
+GREYBUS UART NODE DRIVERS +M: Ayush Singh ayush@beagleboard.com +L: greybus-dev@lists.linaro.org (moderated for non-subscribers) +S: Maintained +F: drivers/greybus/gb_uart_node.rs + GREYBUS SUBSYSTEM M: Johan Hovold johan@kernel.org M: Alex Elder elder@kernel.org diff --git a/drivers/greybus/.gitignore b/drivers/greybus/.gitignore new file mode 100644 index 000000000000..ff9c4a3539b4 --- /dev/null +++ b/drivers/greybus/.gitignore @@ -0,0 +1 @@ +exports_gb_softsvc_generated.h diff --git a/drivers/greybus/Kconfig b/drivers/greybus/Kconfig index 30bc491841e1..b6f687e6da1a 100644 --- a/drivers/greybus/Kconfig +++ b/drivers/greybus/Kconfig @@ -53,5 +53,20 @@ config GREYBUS_SOFTSVC To compile this code as a module, choose M here: the module will be called gb-softsvc.ko
+config GREYBUS_UART_NODE + tristate "Greybus UART node transport" + depends on RUST + depends on GREYBUS_SOFTSVC + depends on RUST_SERIAL_DEV_BUS_ABSTRACTIONS + select RUST_CRC_CCITT_ABSTRACTIONS + help + Select this option if you have a Greybus node connected over a + serial port. The node is registered with the software SVC, which + handles the SVC protocol on behalf of the AP, so no dedicated + coprocessor running SVC firmware is required. + + To compile this code as a module, choose M here: the module + will be called gb-uart-node.ko + endif # GREYBUS
diff --git a/drivers/greybus/Makefile b/drivers/greybus/Makefile index e6f594128802..81151963c01e 100644 --- a/drivers/greybus/Makefile +++ b/drivers/greybus/Makefile @@ -28,3 +28,51 @@ obj-$(CONFIG_GREYBUS_ES2) += gb-es2.o obj-$(CONFIG_GREYBUS_SOFTSVC) += gb-softsvc.o gb-softsvc-y += gb_softsvc.o gb_softsvc_exports.o
+obj-$(CONFIG_GREYBUS_UART_NODE) += gb-uart-node.o +gb-uart-node-y += gb_uart_node.o + +# Export Rust symbols from gb-softsvc only if gb-uart-node actually references them. +gb-softsvc-export-deps := $(if $(CONFIG_GREYBUS_UART_NODE),$(obj)/gb_uart_node.o) + +rust_needed_exports = \ + { $(if $(strip $(2)),$(NM) -u $(2);,) echo "__DEFINED_RUST_SYMBOLS__"; \ + $(NM) -p --defined-only $(1); } | \ + awk -v fmt='$(3)' ' \ + /^__DEFINED_RUST_SYMBOLS__$$/ { defs = 1; next } \ + !defs { if ($$NF ~ /^_R/) needed[$$NF] = 1; next } \ + defs && $$2 ~ /(T|R|D|B)/ && $$3 ~ /^_R/ && \ + $$3 !~ /_(init|cleanup)_module$$/ && \ + $$3 !~ /__(pfx|cfi|odr_asan)/ && \ + $$3 in needed { printf fmt, $$3 } \ + ' + +quiet_cmd_exports = EXPORTS $@ + cmd_exports = \ + $(call rust_needed_exports,$<,$(gb-softsvc-export-deps),EXPORT_SYMBOL_RUST_GPL(%s);\n) > $@ + +$(obj)/exports_gb_softsvc_generated.h: $(obj)/gb_softsvc.o $(gb-softsvc-export-deps) FORCE + $(call if_changed,exports) + +targets += exports_gb_softsvc_generated.h + +$(obj)/gb_softsvc_exports.o: $(obj)/exports_gb_softsvc_generated.h +CFLAGS_gb_softsvc_exports.o := -I $(objtree)/$(obj) + +ifdef CONFIG_MODVERSIONS +# The C export shim declares Rust symbols as `extern int`, so reuse its export +# list but generate symbol CRCs from the Rust object instead of the shim's DWARF. +$(obj)/gb_softsvc_exports.o: private cmd_gensymtypes_c = \ + $(call getexportsymbols,\1) | \ + $(objtree)/scripts/gendwarfksyms/gendwarfksyms \ + $(if $(KBUILD_GENDWARFKSYMS_STABLE), --stable) \ + $(if $(KBUILD_SYMTYPES), --symtypes $(@:.o=.symtypes),) \ + $(obj)/gb_softsvc.o +endif + +# Output nova-core's crate metadata for use by nova-drm at compile time. +RUSTFLAGS_gb_softsvc.o += \ + --emit=metadata=$(objtree)/$(obj)/libgb_softsvc.rmeta + +# Allow nova-drm to import nova-core's types. +$(obj)/gb_uart_node.o: $(obj)/gb_softsvc.o +RUSTFLAGS_gb_uart_node.o := -L $(objtree)/$(obj) --extern gb_softsvc diff --git a/drivers/greybus/gb_uart_node.rs b/drivers/greybus/gb_uart_node.rs new file mode 100644 index 000000000000..125812246758 --- /dev/null +++ b/drivers/greybus/gb_uart_node.rs @@ -0,0 +1,231 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Greybus UART Node driver + +use kernel::crc_ccitt::crc_ccitt; +use kernel::device::AsBusDevice; +use kernel::device::{Bound, Core}; +use kernel::error::code; +use kernel::sync::aref::ARef; +use kernel::sync::{Arc, SpinLock}; +use kernel::{new_spinlock, of, prelude::*, serdev}; + +use zerocopy::little_endian; +use zerocopy_derive::{FromBytes, Immutable, KnownLayout}; + +const HDLC_MAX_FRAME_LEN: usize = 256; + +const HDLC_FRAME: u8 = 0x7E; +const HDLC_ESC: u8 = 0x7D; +const HDLC_XOR: u8 = 0x20; +const HDLC_EXPECTED_CRC: u16 = 0xf0b8; + +const ADDRESS_GREYBUS: u8 = 0x01; + +#[repr(C, packed)] +#[derive(FromBytes, Immutable, KnownLayout)] +struct GreybusFrame { + cport: little_endian::U16, + msg: [u8], +} + +struct HdlcRx { + rx_buf: KVec<u8>, + rx_in_esc: bool, + sdev: ARefserdev::Device, + node: gb_softsvc::Module, +} + +impl HdlcRx { + fn new(sdev: ARefserdev::Device, node: gb_softsvc::Module) -> Result<Self> { + Ok(Self { + node, + sdev, + rx_buf: KVec::with_capacity(HDLC_MAX_FRAME_LEN, GFP_KERNEL)?, + rx_in_esc: false, + }) + } + + fn frame_finish(&self) -> Result<()> { + if self.rx_buf.len() < 4 { + return Err(code::EFAULT); + } + + let crc = crc_ccitt(0xffff, &self.rx_buf); + if crc != HDLC_EXPECTED_CRC { + dev_warn!(self.sdev.as_ref(), "CRC failed {}", crc); + return Ok(()); + } + + let addr = self.rx_buf[0]; + let _ctrl = self.rx_buf[1]; + let payload = &self.rx_buf[2..self.rx_buf.len() - size_of::<u8>()]; + + match addr { + ADDRESS_GREYBUS => { + let frame = GreybusFrame::ref_from_bytes(payload).map_err(|_| code::EINVAL)?; + self.node.submit_message(frame.cport.into(), &frame.msg) + } + _ => Err(code::EINVAL), + } + } + + fn rx(&mut self, data: &[u8]) -> usize { + for (count, i) in data.iter().enumerate() { + match *i { + HDLC_FRAME => { + if !self.rx_buf.is_empty() { + if let Err(e) = self.frame_finish() { + dev_warn!(self.sdev.as_ref(), "bad frame: {e:?}\n"); + } + } + + self.rx_buf.clear(); + self.rx_in_esc = false; + } + HDLC_ESC => self.rx_in_esc = true, + _ => { + let c = if self.rx_in_esc { *i ^ HDLC_XOR } else { *i }; + self.rx_in_esc = false; + + if self.rx_buf.push(c, GFP_KERNEL).is_err() { + return count; + } + } + } + } + + data.len() + } +} + +struct GbNode { + sdev: ARefserdev::Device, +} + +impl GbNode { + const fn new(sdev: ARefserdev::Device) -> Self { + Self { sdev } + } + + fn write_all(mut crc: u16, bound: &serdev::Device<Bound>, data: &[u8]) -> Result<u16> { + for i in data { + if *i == HDLC_ESC || *i == HDLC_FRAME { + let buf = &[HDLC_ESC, i ^ HDLC_XOR]; + bound.write_all(buf, 0)?; + crc = crc_ccitt(crc, buf); + } else { + bound.write_all(&[*i], 0)?; + crc = crc_ccitt(crc, &[*i]); + } + } + + Ok(crc) + } +} + +impl gb_softsvc::InterfaceOps for GbNode { + fn write(&self, data: &[u8], cport: u16) -> Result<()> { + // SAFETY: `GbNode` only exists while its serdev driver is bound, so the device is in the + // `Bound` state for the duration of this call. + let bound: &serdev::Device<Bound> = + unsafe { serdev::Device::from_device(self.sdev.as_ref().as_bound()) }; + + let mut crc = 0xffff; + + bound.write_all(&[HDLC_FRAME], 0)?; + + crc = Self::write_all(crc, bound, &[ADDRESS_GREYBUS, 0x03])?; + crc = Self::write_all(crc, bound, &cport.to_le_bytes())?; + crc = Self::write_all(crc, bound, data)?; + + crc ^= 0xffff; + Self::write_all(crc, bound, &crc.to_le_bytes())?; + + bound.write_all(&[HDLC_FRAME], 0)?; + + Ok(()) + } +} + +#[pin_data(PinnedDrop)] +struct GbUartNode { + sdev: ARefserdev::Device, + #[pin] + rx: SpinLock<HdlcRx>, +} + +impl GbUartNode { + fn init(sdev: &serdev::Device<Core<'_>>) -> Result<HdlcRx> { + if sdev + .set_baudrate( + sdev.as_ref() + .fwnode() + .and_then(|fwnode| fwnode.property_read(c"baudrate").optional()) + .unwrap_or(115200), + ) + .is_err() + { + return Err(EINVAL); + } + sdev.set_flow_control(false); + sdev.set_parity(serdev::Parity::None)?; + + let node = gb_softsvc::Module::new(&[Arc::new(GbNode::new(sdev.into()), GFP_KERNEL)?])?; + + HdlcRx::new(sdev.into(), node) + } +} + +kernel::of_device_table!( + OF_TABLE, + <GbUartNode as serdev::Driver>::IdInfo, + [(of::DeviceId::new(c"beagle,beagleconnect-freedom"), ())] +); + +#[vtable] +impl serdev::Driver for GbUartNode { + type IdInfo = (); + type Data<'bound> = Self; + const OF_ID_TABLE: Option<of::IdTableSelf::IdInfo> = Some(&OF_TABLE); + + fn probe<'bound>( + sdev: &'bound serdev::Device<Core<'_>>, + _info: Option<&'bound Self::IdInfo>, + ) -> impl PinInit<Self, Error> + 'bound { + dev_dbg!(sdev.as_ref(), "Probe gb_uart_node.\n"); + let rx = Self::init(sdev); + + try_pin_init!(Self { + sdev: sdev.into(), + rx <- new_spinlock!(rx?, "gb_uart_node::rx"), + }? Error) + } + + fn receive<'bound>( + _sdev: &'bound serdev::Device<Bound>, + this: Pin<&Self>, + data: &[u8], + ) -> usize { + let Some(mut guard) = this.rx.try_lock() else { + return 0; + }; + + guard.rx(data) + } +} + +#[pinned_drop] +impl PinnedDrop for GbUartNode { + fn drop(self: Pin<&mut Self>) { + dev_dbg!(self.sdev.as_ref(), "Remove gb_uart_node.\n"); + } +} + +kernel::module_serdev_device_driver! { + type: GbUartNode, + name: "gb_uart_node", + authors: ["Ayush Singh ayush@beagleboard.org"], + description: "Greybus node connected over UART", + license: "GPL v2", +}