diff options
Diffstat (limited to 'drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c')
| -rw-r--r-- | drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c new file mode 100644 index 000000000000..4d9eb0137f8c --- /dev/null +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c @@ -0,0 +1,239 @@ +/* + * Copyright 2021 Advanced Micro Devices, Inc. + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR + * OTHER DEALINGS IN THE SOFTWARE. + * + */ + +#include "amdgpu_eeprom.h" +#include "amdgpu.h" + +/* AT24CM02 and M24M02-R have a 256-byte write page size. + */ +#define EEPROM_PAGE_BITS 8 +#define EEPROM_PAGE_SIZE (1U << EEPROM_PAGE_BITS) +#define EEPROM_PAGE_MASK (EEPROM_PAGE_SIZE - 1) + +#define EEPROM_OFFSET_SIZE 2 + +/* EEPROM memory addresses are 19-bits long, which can + * be partitioned into 3, 8, 8 bits, for a total of 19. + * The upper 3 bits are sent as part of the 7-bit + * "Device Type Identifier"--an I2C concept, which for EEPROM devices + * is hard-coded as 1010b, indicating that it is an EEPROM + * device--this is the wire format, followed by the upper + * 3 bits of the 19-bit address, followed by the direction, + * followed by two bytes holding the rest of the 16-bits of + * the EEPROM memory address. The format on the wire for EEPROM + * devices is: 1010XYZD, A15:A8, A7:A0, + * Where D is the direction and sequenced out by the hardware. + * Bits XYZ are memory address bits 18, 17 and 16. + * These bits are compared to how pins 1-3 of the part are connected, + * depending on the size of the part, more on that later. + * + * Note that of this wire format, a client is in control + * of, and needs to specify only XYZ, A15:A8, A7:0, bits, + * which is exactly the EEPROM memory address, or offset, + * in order to address up to 8 EEPROM devices on the I2C bus. + * + * For instance, a 2-Mbit I2C EEPROM part, addresses all its bytes, + * using an 18-bit address, bit 17 to 0 and thus would use all but one bit of + * the 19 bits previously mentioned. The designer would then not connect + * pins 1 and 2, and pin 3 usually named "A_2" or "E2", would be connected to + * either Vcc or GND. This would allow for up to two 2-Mbit parts on + * the same bus, where one would be addressable with bit 18 as 1, and + * the other with bit 18 of the address as 0. + * + * For a 2-Mbit part, bit 18 is usually known as the "Chip Enable" or + * "Hardware Address Bit". This bit is compared to the load on pin 3 + * of the device, described above, and if there is a match, then this + * device responds to the command. This way, you can connect two + * 2-Mbit EEPROM devices on the same bus, but see one contiguous + * memory from 0 to 7FFFFh, where address 0 to 3FFFF is in the device + * whose pin 3 is connected to GND, and address 40000 to 7FFFFh is in + * the 2nd device, whose pin 3 is connected to Vcc. + * + * This addressing you encode in the 32-bit "eeprom_addr" below, + * namely the 19-bits "XYZ,A15:A0", as a single 19-bit address. For + * instance, eeprom_addr = 0x6DA01, is 110_1101_1010_0000_0001, where + * XYZ=110b, and A15:A0=DA01h. The XYZ bits become part of the device + * address, and the rest of the address bits are sent as the memory + * address bytes. + * + * That is, for an I2C EEPROM driver everything is controlled by + * the "eeprom_addr". + * + * P.S. If you need to write, lock and read the Identification Page, + * (M24M02-DR device only, which we do not use), change the "7" to + * "0xF" in the macro below, and let the client set bit 20 to 1 in + * "eeprom_addr", and set A10 to 0 to write into it, and A10 and A1 to + * 1 to lock it permanently. + */ +#define MAKE_I2C_ADDR(_aa) ((0xA << 3) | (((_aa) >> 16) & 7)) + +static int __amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr, + u8 *eeprom_buf, u16 buf_size, bool read) +{ + u8 eeprom_offset_buf[EEPROM_OFFSET_SIZE]; + struct i2c_msg msgs[] = { + { + .flags = 0, + .len = EEPROM_OFFSET_SIZE, + .buf = eeprom_offset_buf, + }, + { + .flags = read ? I2C_M_RD : 0, + }, + }; + const u8 *p = eeprom_buf; + int r; + u16 len; + + for (r = 0; buf_size > 0; + buf_size -= len, eeprom_addr += len, eeprom_buf += len) { + /* Set the EEPROM address we want to write to/read from. + */ + msgs[0].addr = MAKE_I2C_ADDR(eeprom_addr); + msgs[1].addr = msgs[0].addr; + msgs[0].buf[0] = (eeprom_addr >> 8) & 0xff; + msgs[0].buf[1] = eeprom_addr & 0xff; + + if (!read) { + /* Write the maximum amount of data, without + * crossing the device's page boundary, as per + * its spec. Partial page writes are allowed, + * starting at any location within the page, + * so long as the page boundary isn't crossed + * over (actually the page pointer rolls + * over). + * + * As per the AT24CM02 EEPROM spec, after + * writing into a page, the I2C driver should + * terminate the transfer, i.e. in + * "i2c_transfer()" below, with a STOP + * condition, so that the self-timed write + * cycle begins. This is implied for the + * "i2c_transfer()" abstraction. + */ + len = min(EEPROM_PAGE_SIZE - (eeprom_addr & + EEPROM_PAGE_MASK), + (u32)buf_size); + } else { + /* Reading from the EEPROM has no limitation + * on the number of bytes read from the EEPROM + * device--they are simply sequenced out. + */ + len = buf_size; + } + msgs[1].len = len; + msgs[1].buf = eeprom_buf; + + /* This constitutes a START-STOP transaction. + */ + r = i2c_transfer(i2c_adap, msgs, ARRAY_SIZE(msgs)); + if (r != ARRAY_SIZE(msgs)) + break; + + if (!read) { + /* According to EEPROM specs the length of the + * self-writing cycle, tWR (tW), is 10 ms. + * + * TODO: Use polling on ACK, aka Acknowledge + * Polling, to minimize waiting for the + * internal write cycle to complete, as it is + * usually smaller than tWR (tW). + */ + msleep(10); + } + } + + return r < 0 ? r : eeprom_buf - p; +} + +/** + * amdgpu_eeprom_xfer -- Read/write from/to an I2C EEPROM device + * @i2c_adap: pointer to the I2C adapter to use + * @eeprom_addr: EEPROM address from which to read/write + * @eeprom_buf: pointer to data buffer to read into/write from + * @buf_size: the size of @eeprom_buf + * @read: True if reading from the EEPROM, false if writing + * + * Returns the number of bytes read/written; -errno on error. + */ +static int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr, + u8 *eeprom_buf, u16 buf_size, bool read) +{ + const struct i2c_adapter_quirks *quirks = i2c_adap->quirks; + u16 limit; + + if (!quirks) + limit = 0; + else if (read) + limit = quirks->max_read_len; + else + limit = quirks->max_write_len; + + if (limit == 0) { + return __amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, + eeprom_buf, buf_size, read); + } else if (limit <= EEPROM_OFFSET_SIZE) { + dev_err_ratelimited(&i2c_adap->dev, + "maddr:0x%04X size:0x%02X:quirk max_%s_len must be > %d", + eeprom_addr, buf_size, + read ? "read" : "write", EEPROM_OFFSET_SIZE); + return -EINVAL; + } else { + u16 ps; /* Partial size */ + int res = 0, r; + + /* The "limit" includes all data bytes sent/received, + * which would include the EEPROM_OFFSET_SIZE bytes. + * Account for them here. + */ + limit -= EEPROM_OFFSET_SIZE; + for ( ; buf_size > 0; + buf_size -= ps, eeprom_addr += ps, eeprom_buf += ps) { + ps = min(limit, buf_size); + + r = __amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, + eeprom_buf, ps, read); + if (r < 0) + return r; + res += r; + } + + return res; + } +} + +int amdgpu_eeprom_read(struct i2c_adapter *i2c_adap, + u32 eeprom_addr, u8 *eeprom_buf, + u16 bytes) +{ + return amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, eeprom_buf, bytes, + true); +} + +int amdgpu_eeprom_write(struct i2c_adapter *i2c_adap, + u32 eeprom_addr, u8 *eeprom_buf, + u16 bytes) +{ + return amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, eeprom_buf, bytes, + false); +} |