rust: Add i2c module

Just enough to support NS2009 for now.

rust/Cargo.toml

@@ -6,5 +6,5 @@ members = [
 
 [patch.crates-io]
 riscv-rt = { git = "https://github.com/rust-embedded/riscv-rt.git", rev = "ecc1344ffc9af1c88b3dd76b83ad56284672f888"}
-k210-pac = { git = "https://github.com/riscv-rust/k210-pac.git", rev =  "c24d654f5ad39eecf9758b852d0f54a88cefad3f"}
+k210-pac = { git = "https://github.com/riscv-rust/k210-pac.git", rev =  "18f8bdca27d3befa0a92cea2a784f3f5bfc80ae7"}
 k210-hal = { git = "https://github.com/riscv-rust/k210-hal.git", rev = "725418b922d9bb6d8593ba4087b5d90f49e1b8e7" }

rust/k210-shared/src/soc.rs

@@ -1,6 +1,7 @@
 pub mod fpioa;
 pub mod gpio;
 pub mod gpiohs;
+pub mod i2c;
 pub mod sleep;
 pub mod spi;
 pub mod sysctl;

rust/k210-shared/src/soc/i2c.rs

@@ -0,0 +1,90 @@
+use core::convert::TryInto;
+use core::result::Result;
+use k210_hal::pac;
+
+use crate::soc::sysctl;
+
+// TODO parametrize type, other I2C than I2C0
+fn clk_init()
+{
+    sysctl::clock_enable(sysctl::clock::I2C0);
+    sysctl::clock_set_threshold(sysctl::threshold::I2C0, 3);
+}
+
+pub fn init(slave_address: u16, address_width: u32, i2c_clk: u32)
+{
+    assert!(address_width == 7 || address_width == 10);
+
+    clk_init();
+
+    let v_i2c_freq = sysctl::clock_get_freq(sysctl::clock::I2C0);
+    let v_period_clk_cnt = v_i2c_freq / i2c_clk / 2;
+    let v_period_clk_cnt: u16 = v_period_clk_cnt.try_into().unwrap();
+    let v_period_clk_cnt = if v_period_clk_cnt == 0 { 1 } else { v_period_clk_cnt };
+
+    unsafe {
+        let ptr = pac::I2C0::ptr();
+        (*ptr).enable.write(|w| w.bits(0));
+        (*ptr).con.write(|w| w.master_mode().bit(true)
+                             .slave_disable().bit(true)
+                             .restart_en().bit(true)
+                             .addr_slave_width().bit(address_width == 10) // TODO variant
+                             .speed().bits(1)); // TODO variant
+        (*ptr).ss_scl_hcnt.write(|w| w.count().bits(v_period_clk_cnt));
+        (*ptr).ss_scl_lcnt.write(|w| w.count().bits(v_period_clk_cnt));
+        (*ptr).tar.write(|w| w.address().bits(slave_address));
+        (*ptr).intr_mask.write(|w| w.bits(0));
+        (*ptr).dma_cr.write(|w| w.bits(0x3));
+        (*ptr).dma_rdlr.write(|w| w.bits(0));
+        (*ptr).dma_tdlr.write(|w| w.bits(4));
+        (*ptr).enable.write(|w| w.enable().bit(true));
+    }
+}
+
+pub fn recv_data(send_buf: &[u8], receive_buf: &mut [u8]) -> Result<(), ()>
+{
+    unsafe {
+        let ptr = pac::I2C0::ptr();
+        let mut txi = 0;
+        let mut tx_left = send_buf.len();
+        while tx_left != 0 {
+            let fifo_len = 8 - ((*ptr).txflr.read().bits() as usize);
+            let fifo_len = if tx_left < fifo_len { tx_left } else { fifo_len };
+            for _ in 0..fifo_len {
+                (*ptr).data_cmd.write(|w| w.data().bits(send_buf[txi]));
+                txi += 1;
+            }
+            if (*ptr).tx_abrt_source.read().bits() != 0 {
+                return Err(());
+            }
+            tx_left -= fifo_len;
+        }
+
+        let mut cmd_count = receive_buf.len();
+        let mut rx_left = receive_buf.len();
+        let mut rxi = 0;
+        while cmd_count != 0 || rx_left != 0 {
+            /* XXX this is a kind of strange construction, sanity check */
+            let fifo_len = (*ptr).rxflr.read().bits() as usize;
+            let fifo_len = if rx_left < fifo_len { rx_left } else { fifo_len };
+            for _ in 0..fifo_len {
+                receive_buf[rxi] = (*ptr).data_cmd.read().data().bits();
+                rxi += 1;
+            }
+            rx_left -= fifo_len;
+
+            /* send 0x100 for every byte that we want to receive */
+            let fifo_len = 8 - (*ptr).txflr.read().bits() as usize;
+            let fifo_len = if cmd_count < fifo_len { cmd_count } else { fifo_len };
+            for _ in 0..fifo_len {
+                (*ptr).data_cmd.write(|w| w.cmd().bit(true));
+            }
+            if (*ptr).tx_abrt_source.read().bits() != 0 {
+                return Err(());
+            }
+            cmd_count -= fifo_len;
+        }
+    }
+    Ok(())
+}
+