From 746b584762e45206279a5f6b3e4d475f8db245a0 Mon Sep 17 00:00:00 2001 From: Luben Tuikov Date: Wed, 27 Jan 2021 17:09:52 -0500 Subject: [PATCH] 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 Cc: Alexander Deucher Cc: Andrey Grodzovsky Cc: Lijo Lazar Cc: Stanley Yang Cc: Hawking Zhang Signed-off-by: Luben Tuikov Acked-by: Alexander Deucher Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c | 96 +++++++++++++++++++++--------- 1 file changed, 68 insertions(+), 28 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c index d02ea08..7fdb5bd 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c @@ -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; + + 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; - 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; } -- 2.7.4