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746b584762
* When reading from the EEPROM device, there is no device limitation on the number of bytes read--they're simply sequenced out. Thus, read the whole data requested in one go. * When writing to the EEPROM device, there is a 256-byte page limit to write to before having to generate a STOP on the bus, as well as the address written to mustn't cross over the page boundary (it actually rolls over). Maximize the data written to per bus acquisition. * Return the number of bytes read/written, or -errno. * Add kernel doc. Cc: Jean Delvare <jdelvare@suse.de> Cc: Alexander Deucher <Alexander.Deucher@amd.com> Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com> Cc: Lijo Lazar <Lijo.Lazar@amd.com> Cc: Stanley Yang <Stanley.Yang@amd.com> Cc: Hawking Zhang <Hawking.Zhang@amd.com> Signed-off-by: Luben Tuikov <luben.tuikov@amd.com> Acked-by: Alexander Deucher <Alexander.Deucher@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
122 lines
3.8 KiB
C
122 lines
3.8 KiB
C
/*
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* Copyright 2021 Advanced Micro Devices, Inc.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*
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*/
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#include "amdgpu_eeprom.h"
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#include "amdgpu.h"
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/* AT24CM02 has a 256-byte write page size.
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*/
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#define EEPROM_PAGE_BITS 8
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#define EEPROM_PAGE_SIZE (1U << EEPROM_PAGE_BITS)
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#define EEPROM_PAGE_MASK (EEPROM_PAGE_SIZE - 1)
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#define EEPROM_OFFSET_SIZE 2
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/**
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* amdgpu_eeprom_xfer -- Read/write from/to an I2C EEPROM device
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* @i2c_adap: pointer to the I2C adapter to use
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* @slave_addr: I2C address of the slave device
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* @eeprom_addr: EEPROM address from which to read/write
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* @eeprom_buf: pointer to data buffer to read into/write from
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* @buf_size: the size of @eeprom_buf
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* @read: True if reading from the EEPROM, false if writing
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*
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* Returns the number of bytes read/written; -errno on error.
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*/
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int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap,
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u16 slave_addr, u16 eeprom_addr,
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u8 *eeprom_buf, u16 buf_size, bool read)
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{
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u8 eeprom_offset_buf[EEPROM_OFFSET_SIZE];
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struct i2c_msg msgs[] = {
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{
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.addr = slave_addr,
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.flags = 0,
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.len = EEPROM_OFFSET_SIZE,
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.buf = eeprom_offset_buf,
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},
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{
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.addr = slave_addr,
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.flags = read ? I2C_M_RD : 0,
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},
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};
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const u8 *p = eeprom_buf;
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int r;
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u16 len;
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r = 0;
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for (len = 0; buf_size > 0;
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buf_size -= len, eeprom_addr += len, eeprom_buf += len) {
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/* Set the EEPROM address we want to write to/read from.
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*/
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msgs[0].buf[0] = (eeprom_addr >> 8) & 0xff;
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msgs[0].buf[1] = eeprom_addr & 0xff;
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if (!read) {
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/* Write the maximum amount of data, without
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* crossing the device's page boundary, as per
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* its spec. Partial page writes are allowed,
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* starting at any location within the page,
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* so long as the page boundary isn't crossed
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* over (actually the page pointer rolls
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* over).
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*
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* As per the AT24CM02 EEPROM spec, after
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* writing into a page, the I2C driver MUST
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* terminate the transfer, i.e. in
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* "i2c_transfer()" below, with a STOP
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* condition, so that the self-timed write
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* cycle begins. This is implied for the
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* "i2c_transfer()" abstraction.
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*/
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len = min(EEPROM_PAGE_SIZE - (eeprom_addr &
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EEPROM_PAGE_MASK),
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(u32)buf_size);
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} else {
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/* Reading from the EEPROM has no limitation
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* on the number of bytes read from the EEPROM
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* device--they are simply sequenced out.
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*/
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len = buf_size;
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}
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msgs[1].len = len;
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msgs[1].buf = eeprom_buf;
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r = i2c_transfer(i2c_adap, msgs, ARRAY_SIZE(msgs));
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if (r < ARRAY_SIZE(msgs))
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break;
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if (!read) {
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/* According to the AT24CM02 EEPROM spec the
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* length of the self-writing cycle, tWR, is
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* 10 ms.
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*
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* TODO Improve to wait for first ACK for slave address after
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* internal write cycle done.
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*/
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msleep(10);
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}
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}
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return r < 0 ? r : eeprom_buf - p;
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}
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