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drm/amdgpu: Fixes to the AMDGPU EEPROM driver

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* 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>
This commit is contained in:
Luben Tuikov 2021-01-27 17:09:52 -05:00 committed by Alex Deucher
parent daaa75fd98
commit 746b584762
1 changed files with 68 additions and 28 deletions
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96
drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c
View File

@ -24,59 +24,99 @@
#include "amdgpu_eeprom.h"
#include "amdgpu.h"
#define EEPROM_OFFSET_LENGTH 2
/* 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 bytes, bool read)
u8 *eeprom_buf, u16 buf_size, bool read)
{
u8 eeprom_offset_buf[2];
u16 bytes_transferred;
u8 eeprom_offset_buf[EEPROM_OFFSET_SIZE];
struct i2c_msg msgs[] = {
{
.addr = slave_addr,
.flags = 0,
.len = EEPROM_OFFSET_LENGTH,
.len = EEPROM_OFFSET_SIZE,
.buf = eeprom_offset_buf,
},
{
.addr = slave_addr,
.flags = read ? I2C_M_RD : 0,
.len = bytes,
.buf = eeprom_buf,
},
};
const u8 *p = eeprom_buf;
int r;
u16 len;
msgs[0].buf[0] = ((eeprom_addr >> 8) & 0xff);
msgs[0].buf[1] = (eeprom_addr & 0xff);
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;
while (msgs[1].len) {
r = i2c_transfer(i2c_adap, msgs, ARRAY_SIZE(msgs));
if (r <= 0)
return r;
if (r < ARRAY_SIZE(msgs))
break;
/* Only for write data */
if (!msgs[1].flags)
/*
* According to EEPROM spec there is a MAX of 10 ms required for
* EEPROM to flush internal RX buffer after STOP was issued at the
* end of write transaction. During this time the EEPROM will not be
* responsive to any more commands - so wait a bit more.
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);
bytes_transferred = r - EEPROM_OFFSET_LENGTH;
eeprom_addr += bytes_transferred;
msgs[0].buf[0] = ((eeprom_addr >> 8) & 0xff);
msgs[0].buf[1] = (eeprom_addr & 0xff);
msgs[1].buf += bytes_transferred;
msgs[1].len -= bytes_transferred;
}
}
return 0;
return r < 0 ? r : eeprom_buf - p;
}