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/* SPDX-License-Identifier: GPL-2.0-only */
#include <console/console.h>
#include <device/dram/rcd.h>
#include <endian.h>
#include <lib.h>
/**
* Registering Clock Driver (RCD) is responsible for driving address and control
* nets on RDIMM and LRDIMM applications. Its operation is configurable by a set
* of Register Control Words (RCWs). There are two ways of accessing RCWs:
* in-band on the memory channel as an MRS commands ("MR7") or through I2C.
*
* From JESD82-31: "For changes to the control word setting, (...) the
* controller needs to wait tMRD after _the last control word access_, before
* further access _to the DRAM_ can take place". MRS is passed to rank 0 of the
* DRAM, but MR7 is reserved so it is ignored by DRAM. tMRD (8nCK) applies here,
* unless longer delay is needed for RCWs which control the clock timing (see
* JESD82-31 for list of such). This makes sense from DRAMs point of view,
* however we are talking to the Registering Clock Driver (RCD), not DRAM. From
* parts marked in the sentence above one may assume that only one delay at the
* end is necessary and RCWs can be written back to back; however, in the same
* document in table 141 tMRD is defined as "Number of clock cycles between two
* control word accesses, MRS accesses, or any DRAM commands".
*
* I2C access to RCWs is required to support byte (8b), word (16b) and double
* word (32b) write size. Bigger blocks are not required. Reads must always be
* 32b, 32b-aligned blocks, even when reading just one RCW. RCD ignores the two
* lowest bits so unaligned accesses would return shifted values. RCWs are
* tightly packed in I2C space, so it is not possible to write just one 4b RCW
* without writing its neighbor. This is especially important for F0RC06,
* Command Space Control Word, as it is able to reset the state of RCD. For this
* reason, the mentioned register has NOP command (all 1's). JESD82-31 does not
* specify timeouts required for such multi-RCWs writes, or any other writes.
* These are not MRS accesses, so it would be strange to apply those timeouts.
* Perhaps only the registers that actually change the clock settings require
* time to stabilize. On the other hand, I2C is relatively slow, so it is
* possible that the write itself is long enough.
*
* RCD I2C address is 0xBx (or 0x58 + DIMM number, depending on convention), it
* is located on the same bus as SPD. It uses a bus command encoding, see
* section 3.3 in JESD82-31 for description of reading and writing register
* values.
*
* This file includes only functions for access through I2C - it is generic,
* while MRS commands are passed to memory controller registers in an
* implementation specific way.
*/
#define RCD_CMD_BEGIN 0x80
#define RCD_CMD_END 0x40
#define RCD_CMD_PEC 0x10
#define RCD_CMD_RD_DWORD 0x00
#define RCD_CMD_WR_BYTE 0x04
#define RCD_CMD_WR_WORD 0x08
#define RCD_CMD_WR_DWORD 0x0C
#define RCD_CMD_BUS_BYTE 0x00
#define RCD_CMD_BUS_BLOCK 0x02
/* Shorthand for block transfers */
#define RCD_CMD_BLOCK (RCD_CMD_BEGIN | RCD_CMD_END | RCD_CMD_BUS_BLOCK)
/* Excluding size of data */
#define RCD_CMD_BYTES 4
/* Use byte fields to get rid of endianness issues. */
struct rcd_i2c_cmd {
uint8_t cmd;
uint8_t bytes; /* From next byte up to PEC (excluding) */
uint8_t reserved;
uint8_t devfun;
uint8_t reg_h;
uint8_t reg_l;
union { /* Not used for reads, can use 1, 2 or 4 for writes */
uint8_t bdata;
uint32_t ddata;
};
/* Optional PEC */
} __packed;
#define RCD_STS_SUCCESS 0x01
#define RCD_STS_INTERNAL_TARGET_ABORT 0x10
/* Always 4 bytes data + status (for block commands) */
#define RCD_RSP_BYTES 5
struct rcd_i2c_rsp {
uint8_t bytes; /* From next byte up to PEC (excluding) */
uint8_t status;
union {
uint8_t bdata;
uint32_t ddata;
};
/* Optional PEC */
} __packed;
/* Reads a register storing its value in the host's byte order. Returns non-zero on success. */
static int rcd_readd(unsigned int bus, uint8_t slave, uint8_t reg, uint32_t *data)
{
struct i2c_msg seg[2];
struct rcd_i2c_cmd cmd = {
.cmd = RCD_CMD_BLOCK | RCD_CMD_RD_DWORD,
.bytes = RCD_CMD_BYTES,
.reg_l = reg
};
struct rcd_i2c_rsp rsp = { 0xaa, 0x55 };
seg[0].flags = 0;
seg[0].slave = slave;
seg[0].buf = (uint8_t *)&cmd;
seg[0].len = cmd.bytes + 2; /* + .cmd and .bytes fields */
i2c_transfer(bus, seg, 1);
seg[0].len = 1; /* Send just the command again */
seg[1].flags = I2C_M_RD;
seg[1].slave = slave;
seg[1].buf = (uint8_t *)&rsp;
seg[1].len = RCD_RSP_BYTES + 1; /* + .bytes field */
i2c_transfer(bus, seg, ARRAY_SIZE(seg));
/* Data is sent MSB to LSB, i.e. higher registers to lower. */
*data = be32toh(rsp.ddata);
return rsp.status == RCD_STS_SUCCESS;
}
static int rcd_writed(unsigned int bus, uint8_t slave, uint8_t reg, uint32_t data)
{
struct i2c_msg seg;
struct rcd_i2c_cmd cmd = {
.cmd = RCD_CMD_BLOCK | RCD_CMD_WR_DWORD,
.bytes = RCD_CMD_BYTES + sizeof(data),
.reg_l = reg,
/* Data is sent MSB to LSB, i.e. higher registers to lower. */
.ddata = htobe32(data)
};
seg.flags = 0;
seg.slave = slave;
seg.buf = (uint8_t *)&cmd;
seg.len = cmd.bytes + 2; /* + .cmd and .bytes fields */
return i2c_transfer(bus, &seg, 1);
}
static int rcd_writeb(unsigned int bus, uint8_t slave, uint8_t reg, uint8_t data)
{
struct i2c_msg seg;
struct rcd_i2c_cmd cmd = {
.cmd = RCD_CMD_BLOCK | RCD_CMD_WR_BYTE,
.bytes = RCD_CMD_BYTES + sizeof(data),
.reg_l = reg,
.bdata = data
};
seg.flags = 0;
seg.slave = slave;
seg.buf = (uint8_t *)&cmd;
seg.len = cmd.bytes + 2; /* + .cmd and .bytes fields */
return i2c_transfer(bus, &seg, 1);
}
int rcd_write_reg(unsigned int bus, uint8_t slave, enum rcw_idx reg,
uint8_t data)
{
if (reg < F0RC00_01 || reg > F0RCFx) {
printk(BIOS_ERR, "Trying to write to illegal RCW %#2.2x\n",
reg);
return 0;
}
return rcd_writeb(bus, slave, reg, data);
}
int rcd_write_32b(unsigned int bus, uint8_t slave, enum rcw_idx reg,
uint32_t data)
{
if (reg < F0RC00_01 || reg > F0RCFx) {
printk(BIOS_ERR, "Trying to write to illegal RCW %#2.2x\n",
reg);
return 0;
}
if (reg & 3) {
/*
* RCD would silently mask out the lowest bits, assume that this
* is not what caller wanted.
*/
printk(BIOS_ERR, "Unaligned RCW %#2.2x, aborting\n", reg);
return 0;
}
return rcd_writed(bus, slave, reg, data);
}
void dump_rcd(unsigned int bus, u8 addr)
{
/* Can only read in 32b chunks */
uint8_t buf[RCW_ALL_ALIGNED];
int i;
for (i = 0; i < RCW_ALL_ALIGNED; i += sizeof(uint32_t)) {
uint32_t data;
if (!rcd_readd(bus, addr, i, &data)) {
printk(BIOS_ERR, "Failed to read RCD (%d-%02x) at offset %#2.2x\n",
bus, addr, i);
return;
}
/* We want to dump memory the way it's stored, so make sure it's in LE. */
*(uint32_t *)&buf[i] = htole32(data);
}
printk(BIOS_DEBUG, "RCD dump for I2C address %#2.2x:\n", addr);
hexdump(buf, sizeof(buf));
}
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