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/*
* 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 has 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
/**
* amdgpu_eeprom_xfer -- Read/write from/to an I2C EEPROM device
* @i2c_adap: pointer to the I2C adapter to use
* @slave_addr: I2C address of the slave device
* @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.
*/
int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap,
u16 slave_addr, u16 eeprom_addr,
u8 *eeprom_buf, u16 buf_size, bool read)
{
u8 eeprom_offset_buf[EEPROM_OFFSET_SIZE];
struct i2c_msg msgs[] = {
{
.addr = slave_addr,
.flags = 0,
.len = EEPROM_OFFSET_SIZE,
.buf = eeprom_offset_buf,
},
{
.addr = slave_addr,
.flags = read ? I2C_M_RD : 0,
},
};
const u8 *p = eeprom_buf;
int r;
u16 len;
r = 0;
for (len = 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].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 MUST
* 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;
r = i2c_transfer(i2c_adap, msgs, ARRAY_SIZE(msgs));
if (r < ARRAY_SIZE(msgs))
break;
if (!read) {
/* According to the AT24CM02 EEPROM spec the
* length of the self-writing cycle, tWR, is
* 10 ms.
*
* TODO Improve to wait for first ACK for slave address after
* internal write cycle done.
*/
msleep(10);
}
}
return r < 0 ? r : eeprom_buf - p;
}
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