opentitanlib/otp/
lc_state.rs

1// Copyright lowRISC contributors (OpenTitan project).
2// Licensed under the Apache License, Version 2.0, see LICENSE for details.
3// SPDX-License-Identifier: Apache-2.0
4
5use anyhow::{Result, bail};
6use serde::Deserialize;
7use std::fs;
8use std::path::Path;
9
10/// SECDED matrix used for ECC in OTP.
11#[derive(Deserialize, Debug)]
12pub struct LcSecded {
13    /// The number of bits of data covered by ECC.
14    data_width: usize,
15    /// The number of ECC bits.
16    ecc_width: usize,
17    /// ECC matrix used for computing ECC bits.
18    ecc_matrix: Vec<Vec<u8>>,
19}
20
21/// The internal representation of lc_ctrl_state, used in OTP operations.
22#[derive(Deserialize, Debug)]
23pub struct LcState {
24    secded: LcSecded,
25}
26
27#[repr(u32)]
28#[derive(Copy, Clone)]
29pub enum LcStateVal {
30    Test = 0xb2865fbb,
31    Dev = 0x0b5a75e0,
32    Prod = 0x65f2520f,
33    ProdEnd = 0x91b9b68a,
34    Rma = 0xcf8cfaab,
35}
36
37impl LcSecded {
38    pub fn new(in_file: &Path) -> Result<LcSecded> {
39        let json_text = fs::read_to_string(in_file)?;
40        let res: LcState = deser_hjson::from_str(&json_text)?;
41        if res.secded.ecc_matrix.len() != res.secded.ecc_width {
42            bail!("Bad ecc matrix length {}", res.secded.ecc_matrix.len());
43        }
44        Ok(res.secded)
45    }
46
47    fn bit_index(data: &[u8], index: usize) -> bool {
48        let byte = index / 8;
49        let bit = index % 8;
50        data[byte] & (1 << bit) != 0
51    }
52
53    pub fn ecc_encode(&self, mut data: Vec<u8>) -> Result<Vec<u8>> {
54        if data.len() * 8 != self.data_width {
55            bail!("Bad data length for ecc {}", data.len() * 8);
56        }
57        let data_len = data.len();
58        data.resize(data_len + self.ecc_byte_len(), 0);
59        for (i, matrix) in self.ecc_matrix.iter().enumerate() {
60            let mut bit = false;
61            for j in matrix {
62                bit ^= Self::bit_index(&data, *j as usize);
63            }
64            if bit {
65                let byte = i / 8 + data_len;
66                let bit = i % 8;
67                data[byte] |= 1 << bit;
68            }
69        }
70
71        Ok(data)
72    }
73
74    pub fn ecc_byte_len(&self) -> usize {
75        if self.ecc_width == 0 {
76            0
77        } else {
78            (self.ecc_width - 1) / 8 + 1
79        }
80    }
81}
82
83#[cfg(test)]
84mod tests {
85    use super::*;
86    use crate::util::testdata;
87    use anyhow::Result;
88    use deser_hjson::from_str;
89    use std::fs::read_to_string;
90
91    #[test]
92    fn test_lc_state_deserialize() -> Result<()> {
93        let _: LcState = from_str(&read_to_string(testdata("otp/lc_ctrl_state.hjson"))?)?;
94        Ok(())
95    }
96
97    #[test]
98    fn test_ecc_encode() {
99        let secded = LcSecded {
100            data_width: 16,
101            ecc_width: 6,
102            ecc_matrix: vec![
103                vec![0, 1, 3, 4, 6, 8, 10, 11, 13, 15], // ECC bit 0
104                vec![0, 2, 3, 5, 6, 9, 10, 12, 13],     // ECC bit 1
105                vec![1, 2, 3, 7, 8, 9, 10, 14, 15],     // ECC bit 2
106                vec![4, 5, 6, 7, 8, 9, 10],             // ECC bit 3
107                vec![11, 12, 13, 14, 15],               // ECC bit 4
108                vec![
109                    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
110                ], // Parity bit
111            ],
112        };
113
114        let zero: Vec<u8> = vec![0, 0];
115        let a5a5: Vec<u8> = vec![0xa5, 0xa5];
116        let fcc5: Vec<u8> = vec![0xfc, 0xc5];
117        assert_eq!(vec![0u8, 0, 0], secded.ecc_encode(zero).unwrap());
118        assert_eq!(vec![0xa5u8, 0xa5, 0x27], secded.ecc_encode(a5a5).unwrap());
119        assert_eq!(vec![0x0fcu8, 0xc5, 0x06], secded.ecc_encode(fcc5).unwrap())
120    }
121}
opentitanlib/otp/lc_state.rs

opentitanlib/otp/
lc_state.rs
