From 854149ee977a71003ed14bc934d7d46b465dcda6 Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jeremy@system76.com>
Date: Sun, 19 Jul 2020 10:24:15 -0600
Subject: [PATCH] Support for debugging to system76 EC

---
 Cargo.toml                            |  1 +
 src/arch/x86_64/debug.rs              | 13 ++++
 src/arch/x86_64/device/mod.rs         |  2 +
 src/arch/x86_64/device/system76_ec.rs | 91 +++++++++++++++++++++++++++
 src/arch/x86_64/start.rs              |  3 +
 5 files changed, 110 insertions(+)
 create mode 100644 src/arch/x86_64/device/system76_ec.rs

diff --git a/Cargo.toml b/Cargo.toml
index d38edb7..21bf399 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -42,4 +42,5 @@ multi_core = ["acpi"]
 pti = []
 qemu_debug = []
 serial_debug = []
+system76_ec_debug = []
 slab = ["slab_allocator"]
diff --git a/src/arch/x86_64/debug.rs b/src/arch/x86_64/debug.rs
index c2dd73a..70f79db 100644
--- a/src/arch/x86_64/debug.rs
+++ b/src/arch/x86_64/debug.rs
@@ -19,6 +19,8 @@ use super::graphical_debug::{DEBUG_DISPLAY, DebugDisplay};
 use super::device::serial::LPSS;
 #[cfg(feature = "serial_debug")]
 use super::device::serial::COM1;
+#[cfg(feature = "system76_ec_debug")]
+use super::device::system76_ec::{SYSTEM76_EC, System76Ec};
 
 #[cfg(feature = "qemu_debug")]
 pub static QEMU: Mutex<Pio<u8>> = Mutex::new(Pio::<u8>::new(0x402));
@@ -33,6 +35,8 @@ pub struct Writer<'a> {
     qemu: MutexGuard<'a, Pio<u8>>,
     #[cfg(feature = "serial_debug")]
     serial: MutexGuard<'a, SerialPort<Pio<u8>>>,
+    #[cfg(feature = "system76_ec_debug")]
+    system76_ec: MutexGuard<'a, Option<System76Ec>>,
 }
 
 impl<'a> Writer<'a> {
@@ -47,6 +51,8 @@ impl<'a> Writer<'a> {
             qemu: QEMU.lock(),
             #[cfg(feature = "serial_debug")]
             serial: COM1.lock(),
+            #[cfg(feature = "system76_ec_debug")]
+            system76_ec: SYSTEM76_EC.lock(),
         }
     }
 
@@ -82,6 +88,13 @@ impl<'a> Writer<'a> {
         {
             self.serial.write(buf);
         }
+
+        #[cfg(feature = "system76_ec_debug")]
+        {
+            if let Some(ref mut system76_ec) = *self.system76_ec {
+                system76_ec.print_slice(buf);
+            }
+        }
     }
 }
 
diff --git a/src/arch/x86_64/device/mod.rs b/src/arch/x86_64/device/mod.rs
index 9460f65..e5e8601 100644
--- a/src/arch/x86_64/device/mod.rs
+++ b/src/arch/x86_64/device/mod.rs
@@ -9,6 +9,8 @@ pub mod rtc;
 pub mod serial;
 #[cfg(feature = "acpi")]
 pub mod hpet;
+#[cfg(feature = "system76_ec_debug")]
+pub mod system76_ec;
 
 pub unsafe fn init(active_table: &mut ActivePageTable) {
     pic::init();
diff --git a/src/arch/x86_64/device/system76_ec.rs b/src/arch/x86_64/device/system76_ec.rs
new file mode 100644
index 0000000..49f3a29
--- /dev/null
+++ b/src/arch/x86_64/device/system76_ec.rs
@@ -0,0 +1,91 @@
+use spin::Mutex;
+use syscall::io::{Io, Pio};
+
+pub static SYSTEM76_EC: Mutex<Option<System76Ec>> = Mutex::new(None);
+
+pub fn init() {
+    *SYSTEM76_EC.lock() = System76Ec::new();
+}
+
+pub struct System76Ec {
+    base: u16,
+}
+
+impl System76Ec {
+    pub fn new() -> Option<Self> {
+        let mut system76_ec = Self {
+            base: 0x0E00,
+        };
+        if system76_ec.probe() {
+            Some(system76_ec)
+        } else {
+            None
+        }
+    }
+
+    #[inline(always)]
+    pub fn read(&mut self, addr: u8) -> u8 {
+        Pio::<u8>::new(self.base + addr as u16).read()
+    }
+
+    #[inline(always)]
+    pub fn write(&mut self, addr: u8, data: u8) {
+        Pio::<u8>::new(self.base + addr as u16).write(data)
+    }
+
+    pub fn probe(&mut self) -> bool {
+        // Send probe command
+        self.write(0, 1);
+
+        // Wait for response
+        let mut timeout = 1_000_000;
+        while timeout > 0 {
+            if self.read(0) == 0 {
+                break;
+            }
+            timeout -= 1;
+        }
+        if timeout == 0 {
+            return false;
+        }
+
+        // Return false on command error
+        if self.read(1) != 0 {
+            return false;
+        }
+
+        // Must receive 0x76, 0xEC as signature
+        self.read(2) == 0x76 && self.read(3) == 0xEC
+    }
+
+    pub fn flush(&mut self) {
+        // Send command
+        self.write(0, 4);
+
+        // TODO: timeout
+        while self.read(0) != 0 {}
+
+        // Clear length
+        self.write(3, 0);
+    }
+
+    pub fn print(&mut self, byte: u8) {
+        // Read length
+        let len = self.read(3);
+        // Write data at offset
+        self.write(len + 4, byte);
+        // Update length
+        self.write(3, len + 1);
+
+        // If we hit the end of the buffer, or were given a newline, flush
+        if byte == b'\n' || len >= 128 {
+            self.flush();
+        }
+    }
+
+    pub fn print_slice(&mut self, bytes: &[u8]) {
+        for &byte in bytes {
+            self.print(byte);
+        }
+    }
+}
diff --git a/src/arch/x86_64/start.rs b/src/arch/x86_64/start.rs
index 7cdec3d..5829943 100644
--- a/src/arch/x86_64/start.rs
+++ b/src/arch/x86_64/start.rs
@@ -141,6 +141,9 @@ pub unsafe extern fn kstart(args_ptr: *const KernelArgs) -> ! {
         #[cfg(feature="graphical_debug")]
         graphical_debug::init(&mut active_table);
 
+        #[cfg(feature = "system76_ec_debug")]
+        device::system76_ec::init();
+
         // Initialize devices
         device::init(&mut active_table);