Commit 746b5847 authored by Luben Tuikov's avatar Luben Tuikov Committed by Alex Deucher
Browse files

drm/amdgpu: Fixes to the AMDGPU EEPROM driver 



* 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: default avatarLuben Tuikov <luben.tuikov@amd.com>
Acked-by: default avatarAlexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent daaa75fd

drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c

+68 −28
Original line number Diff line number Diff line
@@ -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;

}