1 /* 2 * Copyright 2021 Advanced Micro Devices, Inc. 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining a 5 * copy of this software and associated documentation files (the "Software"), 6 * to deal in the Software without restriction, including without limitation 7 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 8 * and/or sell copies of the Software, and to permit persons to whom the 9 * Software is furnished to do so, subject to the following conditions: 10 * 11 * The above copyright notice and this permission notice shall be included in 12 * all copies or substantial portions of the Software. 13 * 14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 17 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR 18 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 19 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 20 * OTHER DEALINGS IN THE SOFTWARE. 21 * 22 */ 23 24 #include "amdgpu_eeprom.h" 25 #include "amdgpu.h" 26 27 /* AT24CM02 and M24M02-R have a 256-byte write page size. 28 */ 29 #define EEPROM_PAGE_BITS 8 30 #define EEPROM_PAGE_SIZE (1U << EEPROM_PAGE_BITS) 31 #define EEPROM_PAGE_MASK (EEPROM_PAGE_SIZE - 1) 32 33 #define EEPROM_OFFSET_SIZE 2 34 35 /* EEPROM memory addresses are 19-bits long, which can 36 * be partitioned into 3, 8, 8 bits, for a total of 19. 37 * The upper 3 bits are sent as part of the 7-bit 38 * "Device Type Identifier"--an I2C concept, which for EEPROM devices 39 * is hard-coded as 1010b, indicating that it is an EEPROM 40 * device--this is the wire format, followed by the upper 41 * 3 bits of the 19-bit address, followed by the direction, 42 * followed by two bytes holding the rest of the 16-bits of 43 * the EEPROM memory address. The format on the wire for EEPROM 44 * devices is: 1010XYZD, A15:A8, A7:A0, 45 * Where D is the direction and sequenced out by the hardware. 46 * Bits XYZ are memory address bits 18, 17 and 16. 47 * These bits are compared to how pins 1-3 of the part are connected, 48 * depending on the size of the part, more on that later. 49 * 50 * Note that of this wire format, a client is in control 51 * of, and needs to specify only XYZ, A15:A8, A7:0, bits, 52 * which is exactly the EEPROM memory address, or offset, 53 * in order to address up to 8 EEPROM devices on the I2C bus. 54 * 55 * For instance, a 2-Mbit I2C EEPROM part, addresses all its bytes, 56 * using an 18-bit address, bit 17 to 0 and thus would use all but one bit of 57 * the 19 bits previously mentioned. The designer would then not connect 58 * pins 1 and 2, and pin 3 usually named "A_2" or "E2", would be connected to 59 * either Vcc or GND. This would allow for up to two 2-Mbit parts on 60 * the same bus, where one would be addressable with bit 18 as 1, and 61 * the other with bit 18 of the address as 0. 62 * 63 * For a 2-Mbit part, bit 18 is usually known as the "Chip Enable" or 64 * "Hardware Address Bit". This bit is compared to the load on pin 3 65 * of the device, described above, and if there is a match, then this 66 * device responds to the command. This way, you can connect two 67 * 2-Mbit EEPROM devices on the same bus, but see one contiguous 68 * memory from 0 to 7FFFFh, where address 0 to 3FFFF is in the device 69 * whose pin 3 is connected to GND, and address 40000 to 7FFFFh is in 70 * the 2nd device, whose pin 3 is connected to Vcc. 71 * 72 * This addressing you encode in the 32-bit "eeprom_addr" below, 73 * namely the 19-bits "XYZ,A15:A0", as a single 19-bit address. For 74 * instance, eeprom_addr = 0x6DA01, is 110_1101_1010_0000_0001, where 75 * XYZ=110b, and A15:A0=DA01h. The XYZ bits become part of the device 76 * address, and the rest of the address bits are sent as the memory 77 * address bytes. 78 * 79 * That is, for an I2C EEPROM driver everything is controlled by 80 * the "eeprom_addr". 81 * 82 * P.S. If you need to write, lock and read the Identification Page, 83 * (M24M02-DR device only, which we do not use), change the "7" to 84 * "0xF" in the macro below, and let the client set bit 20 to 1 in 85 * "eeprom_addr", and set A10 to 0 to write into it, and A10 and A1 to 86 * 1 to lock it permanently. 87 */ 88 #define MAKE_I2C_ADDR(_aa) ((0xA << 3) | (((_aa) >> 16) & 7)) 89 90 static int __amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr, 91 u8 *eeprom_buf, u16 buf_size, bool read) 92 { 93 u8 eeprom_offset_buf[EEPROM_OFFSET_SIZE]; 94 struct i2c_msg msgs[] = { 95 { 96 .flags = 0, 97 .len = EEPROM_OFFSET_SIZE, 98 .buf = eeprom_offset_buf, 99 }, 100 { 101 .flags = read ? I2C_M_RD : 0, 102 }, 103 }; 104 const u8 *p = eeprom_buf; 105 int r; 106 u16 len; 107 108 for (r = 0; buf_size > 0; 109 buf_size -= len, eeprom_addr += len, eeprom_buf += len) { 110 /* Set the EEPROM address we want to write to/read from. 111 */ 112 msgs[0].addr = MAKE_I2C_ADDR(eeprom_addr); 113 msgs[1].addr = msgs[0].addr; 114 msgs[0].buf[0] = (eeprom_addr >> 8) & 0xff; 115 msgs[0].buf[1] = eeprom_addr & 0xff; 116 117 if (!read) { 118 /* Write the maximum amount of data, without 119 * crossing the device's page boundary, as per 120 * its spec. Partial page writes are allowed, 121 * starting at any location within the page, 122 * so long as the page boundary isn't crossed 123 * over (actually the page pointer rolls 124 * over). 125 * 126 * As per the AT24CM02 EEPROM spec, after 127 * writing into a page, the I2C driver should 128 * terminate the transfer, i.e. in 129 * "i2c_transfer()" below, with a STOP 130 * condition, so that the self-timed write 131 * cycle begins. This is implied for the 132 * "i2c_transfer()" abstraction. 133 */ 134 len = min(EEPROM_PAGE_SIZE - (eeprom_addr & 135 EEPROM_PAGE_MASK), 136 (u32)buf_size); 137 } else { 138 /* Reading from the EEPROM has no limitation 139 * on the number of bytes read from the EEPROM 140 * device--they are simply sequenced out. 141 */ 142 len = buf_size; 143 } 144 msgs[1].len = len; 145 msgs[1].buf = eeprom_buf; 146 147 /* This constitutes a START-STOP transaction. 148 */ 149 r = i2c_transfer(i2c_adap, msgs, ARRAY_SIZE(msgs)); 150 if (r != ARRAY_SIZE(msgs)) 151 break; 152 153 if (!read) { 154 /* According to EEPROM specs the length of the 155 * self-writing cycle, tWR (tW), is 10 ms. 156 * 157 * TODO: Use polling on ACK, aka Acknowledge 158 * Polling, to minimize waiting for the 159 * internal write cycle to complete, as it is 160 * usually smaller than tWR (tW). 161 */ 162 msleep(10); 163 } 164 } 165 166 return r < 0 ? r : eeprom_buf - p; 167 } 168 169 /** 170 * amdgpu_eeprom_xfer -- Read/write from/to an I2C EEPROM device 171 * @i2c_adap: pointer to the I2C adapter to use 172 * @eeprom_addr: EEPROM address from which to read/write 173 * @eeprom_buf: pointer to data buffer to read into/write from 174 * @buf_size: the size of @eeprom_buf 175 * @read: True if reading from the EEPROM, false if writing 176 * 177 * Returns the number of bytes read/written; -errno on error. 178 */ 179 static int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr, 180 u8 *eeprom_buf, u16 buf_size, bool read) 181 { 182 const struct i2c_adapter_quirks *quirks = i2c_adap->quirks; 183 u16 limit; 184 185 if (!quirks) 186 limit = 0; 187 else if (read) 188 limit = quirks->max_read_len; 189 else 190 limit = quirks->max_write_len; 191 192 if (limit == 0) { 193 return __amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, 194 eeprom_buf, buf_size, read); 195 } else if (limit <= EEPROM_OFFSET_SIZE) { 196 dev_err_ratelimited(&i2c_adap->dev, 197 "maddr:0x%04X size:0x%02X:quirk max_%s_len must be > %d", 198 eeprom_addr, buf_size, 199 read ? "read" : "write", EEPROM_OFFSET_SIZE); 200 return -EINVAL; 201 } else { 202 u16 ps; /* Partial size */ 203 int res = 0, r; 204 205 /* The "limit" includes all data bytes sent/received, 206 * which would include the EEPROM_OFFSET_SIZE bytes. 207 * Account for them here. 208 */ 209 limit -= EEPROM_OFFSET_SIZE; 210 for ( ; buf_size > 0; 211 buf_size -= ps, eeprom_addr += ps, eeprom_buf += ps) { 212 ps = min(limit, buf_size); 213 214 r = __amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, 215 eeprom_buf, ps, read); 216 if (r < 0) 217 return r; 218 res += r; 219 } 220 221 return res; 222 } 223 } 224 225 int amdgpu_eeprom_read(struct i2c_adapter *i2c_adap, 226 u32 eeprom_addr, u8 *eeprom_buf, 227 u16 bytes) 228 { 229 return amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, eeprom_buf, bytes, 230 true); 231 } 232 233 int amdgpu_eeprom_write(struct i2c_adapter *i2c_adap, 234 u32 eeprom_addr, u8 *eeprom_buf, 235 u16 bytes) 236 { 237 return amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, eeprom_buf, bytes, 238 false); 239 } 240