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// SPDX-License-Identifier: GPL-2.0
//
// Register map access API - SPI AVMM support
//
// Copyright (C) 2018-2020 Intel Corporation. All rights reserved.
#include <linux/module.h>
#include <linux/regmap.h>
#include <linux/spi/spi.h>
#include <linux/swab.h>
/*
* This driver implements the regmap operations for a generic SPI
* master to access the registers of the spi slave chip which has an
* Avalone bus in it.
*
* The "SPI slave to Avalon Master Bridge" (spi-avmm) IP should be integrated
* in the spi slave chip. The IP acts as a bridge to convert encoded streams of
* bytes from the host to the internal register read/write on Avalon bus. In
* order to issue register access requests to the slave chip, the host should
* send formatted bytes that conform to the transfer protocol.
* The transfer protocol contains 3 layers: transaction layer, packet layer
* and physical layer.
*
* Reference Documents could be found at:
* https://www.intel.com/content/www/us/en/programmable/documentation/sfo1400787952932.html
*
* Chapter "SPI Slave/JTAG to Avalon Master Bridge Cores" is a general
* introduction to the protocol.
*
* Chapter "Avalon Packets to Transactions Converter Core" describes
* the transaction layer.
*
* Chapter "Avalon-ST Bytes to Packets and Packets to Bytes Converter Cores"
* describes the packet layer.
*
* Chapter "Avalon-ST Serial Peripheral Interface Core" describes the
* physical layer.
*
*
* When host issues a regmap read/write, the driver will transform the request
* to byte stream layer by layer. It formats the register addr, value and
* length to the transaction layer request, then converts the request to packet
* layer bytes stream and then to physical layer bytes stream. Finally the
* driver sends the formatted byte stream over SPI bus to the slave chip.
*
* The spi-avmm IP on the slave chip decodes the byte stream and initiates
* register read/write on its internal Avalon bus, and then encodes the
* response to byte stream and sends back to host.
*
* The driver receives the byte stream, reverses the 3 layers transformation,
* and finally gets the response value (read out data for register read,
* successful written size for register write).
*/
#define PKT_SOP 0x7a
#define PKT_EOP 0x7b
#define PKT_CHANNEL 0x7c
#define PKT_ESC 0x7d
#define PHY_IDLE 0x4a
#define PHY_ESC 0x4d
#define TRANS_CODE_WRITE 0x0
#define TRANS_CODE_SEQ_WRITE 0x4
#define TRANS_CODE_READ 0x10
#define TRANS_CODE_SEQ_READ 0x14
#define TRANS_CODE_NO_TRANS 0x7f
#define SPI_AVMM_XFER_TIMEOUT (msecs_to_jiffies(200))
/* slave's register addr is 32 bits */
#define SPI_AVMM_REG_SIZE 4UL
/* slave's register value is 32 bits */
#define SPI_AVMM_VAL_SIZE 4UL
/*
* max rx size could be larger. But considering the buffer consuming,
* it is proper that we limit 1KB xfer at max.
*/
#define MAX_READ_CNT 256UL
#define MAX_WRITE_CNT 1UL
struct trans_req_header {
u8 code;
u8 rsvd;
__be16 size;
__be32 addr;
} __packed;
struct trans_resp_header {
u8 r_code;
u8 rsvd;
__be16 size;
} __packed;
#define TRANS_REQ_HD_SIZE (sizeof(struct trans_req_header))
#define TRANS_RESP_HD_SIZE (sizeof(struct trans_resp_header))
/*
* In transaction layer,
* the write request format is: Transaction request header + data
* the read request format is: Transaction request header
* the write response format is: Transaction response header
* the read response format is: pure data, no Transaction response header
*/
#define TRANS_WR_TX_SIZE(n) (TRANS_REQ_HD_SIZE + SPI_AVMM_VAL_SIZE * (n))
#define TRANS_RD_TX_SIZE TRANS_REQ_HD_SIZE
#define TRANS_TX_MAX TRANS_WR_TX_SIZE(MAX_WRITE_CNT)
#define TRANS_RD_RX_SIZE(n) (SPI_AVMM_VAL_SIZE * (n))
#define TRANS_WR_RX_SIZE TRANS_RESP_HD_SIZE
#define TRANS_RX_MAX TRANS_RD_RX_SIZE(MAX_READ_CNT)
/* tx & rx share one transaction layer buffer */
#define TRANS_BUF_SIZE ((TRANS_TX_MAX > TRANS_RX_MAX) ? \
TRANS_TX_MAX : TRANS_RX_MAX)
/*
* In tx phase, the host prepares all the phy layer bytes of a request in the
* phy buffer and sends them in a batch.
*
* The packet layer and physical layer defines several special chars for
* various purpose, when a transaction layer byte hits one of these special
* chars, it should be escaped. The escape rule is, "Escape char first,
* following the byte XOR'ed with 0x20".
*
* This macro defines the max possible length of the phy data. In the worst
* case, all transaction layer bytes need to be escaped (so the data length
* doubles), plus 4 special chars (SOP, CHANNEL, CHANNEL_NUM, EOP). Finally
* we should make sure the length is aligned to SPI BPW.
*/
#define PHY_TX_MAX ALIGN(2 * TRANS_TX_MAX + 4, 4)
/*
* Unlike tx, phy rx is affected by possible PHY_IDLE bytes from slave, the max
* length of the rx bit stream is unpredictable. So the driver reads the words
* one by one, and parses each word immediately into transaction layer buffer.
* Only one word length of phy buffer is used for rx.
*/
#define PHY_BUF_SIZE PHY_TX_MAX
/**
* struct spi_avmm_bridge - SPI slave to AVMM bus master bridge
*
* @spi: spi slave associated with this bridge.
* @word_len: bytes of word for spi transfer.
* @trans_len: length of valid data in trans_buf.
* @phy_len: length of valid data in phy_buf.
* @trans_buf: the bridge buffer for transaction layer data.
* @phy_buf: the bridge buffer for physical layer data.
* @swap_words: the word swapping cb for phy data. NULL if not needed.
*
* As a device's registers are implemented on the AVMM bus address space, it
* requires the driver to issue formatted requests to spi slave to AVMM bus
* master bridge to perform register access.
*/
struct spi_avmm_bridge {
struct spi_device *spi;
unsigned char word_len;
unsigned int trans_len;
unsigned int phy_len;
/* bridge buffer used in translation between protocol layers */
char trans_buf[TRANS_BUF_SIZE];
char phy_buf[PHY_BUF_SIZE];
void (*swap_words)(void *buf, unsigned int len);
};
static void br_swap_words_32(void *buf, unsigned int len)
{
swab32_array(buf, len / 4);
}
/*
* Format transaction layer data in br->trans_buf according to the register
* access request, Store valid transaction layer data length in br->trans_len.
*/
static int br_trans_tx_prepare(struct spi_avmm_bridge *br, bool is_read, u32 reg,
u32 *wr_val, u32 count)
{
struct trans_req_header *header;
unsigned int trans_len;
u8 code;
__le32 *data;
int i;
if (is_read) {
if (count == 1)
code = TRANS_CODE_READ;
else
code = TRANS_CODE_SEQ_READ;
} else {
if (count == 1)
code = TRANS_CODE_WRITE;
else
code = TRANS_CODE_SEQ_WRITE;
}
header = (struct trans_req_header *)br->trans_buf;
header->code = code;
header->rsvd = 0;
header->size = cpu_to_be16((u16)count * SPI_AVMM_VAL_SIZE);
header->addr = cpu_to_be32(reg);
trans_len = TRANS_REQ_HD_SIZE;
if (!is_read) {
trans_len += SPI_AVMM_VAL_SIZE * count;
if (trans_len > sizeof(br->trans_buf))
return -ENOMEM;
data = (__le32 *)(br->trans_buf + TRANS_REQ_HD_SIZE);
for (i = 0; i < count; i++)
*data++ = cpu_to_le32(*wr_val++);
}
/* Store valid trans data length for next layer */
br->trans_len = trans_len;
return 0;
}
/*
* Convert transaction layer data (in br->trans_buf) to phy layer data, store
* them in br->phy_buf. Pad the phy_buf aligned with SPI's BPW. Store valid phy
* layer data length in br->phy_len.
*
* phy_buf len should be aligned with SPI's BPW. Spare bytes should be padded
* with PHY_IDLE, then the slave will just drop them.
*
* The driver will not simply pad 4a at the tail. The concern is that driver
* will not store MISO data during tx phase, if the driver pads 4a at the tail,
* it is possible that if the slave is fast enough to response at the padding
* time. As a result these rx bytes are lost. In the following case, 7a,7c,00
* will lost.
* MOSI ...|7a|7c|00|10| |00|00|04|02| |4b|7d|5a|7b| |40|4a|4a|4a| |XX|XX|...
* MISO ...|4a|4a|4a|4a| |4a|4a|4a|4a| |4a|4a|4a|4a| |4a|7a|7c|00| |78|56|...
*
* So the driver moves EOP and bytes after EOP to the end of the aligned size,
* then fill the hole with PHY_IDLE. As following:
* before pad ...|7a|7c|00|10| |00|00|04|02| |4b|7d|5a|7b| |40|
* after pad ...|7a|7c|00|10| |00|00|04|02| |4b|7d|5a|4a| |4a|4a|7b|40|
* Then if the slave will not get the entire packet before the tx phase is
* over, it can't responsed to anything either.
*/
static int br_pkt_phy_tx_prepare(struct spi_avmm_bridge *br)
{
char *tb, *tb_end, *pb, *pb_limit, *pb_eop = NULL;
unsigned int aligned_phy_len, move_size;
bool need_esc = false;
tb = br->trans_buf;
tb_end = tb + br->trans_len;
pb = br->phy_buf;
pb_limit = pb + ARRAY_SIZE(br->phy_buf);
*pb++ = PKT_SOP;
/*
* The driver doesn't support multiple channels so the channel number
* is always 0.
*/
*pb++ = PKT_CHANNEL;
*pb++ = 0x0;
for (; pb < pb_limit && tb < tb_end; pb++) {
if (need_esc) {
*pb = *tb++ ^ 0x20;
need_esc = false;
continue;
}
/* EOP should be inserted before the last valid char */
if (tb == tb_end - 1 && !pb_eop) {
*pb = PKT_EOP;
pb_eop = pb;
continue;
}
/*
* insert an ESCAPE char if the data value equals any special
* char.
*/
switch (*tb) {
case PKT_SOP:
case PKT_EOP:
case PKT_CHANNEL:
case PKT_ESC:
*pb = PKT_ESC;
need_esc = true;
break;
case PHY_IDLE:
case PHY_ESC:
*pb = PHY_ESC;
need_esc = true;
break;
default:
*pb = *tb++;
break;
}
}
/* The phy buffer is used out but transaction layer data remains */
if (tb < tb_end)
return -ENOMEM;
/* Store valid phy data length for spi transfer */
br->phy_len = pb - br->phy_buf;
if (br->word_len == 1)
return 0;
/* Do phy buf padding if word_len > 1 byte. */
aligned_phy_len = ALIGN(br->phy_len, br->word_len);
if (aligned_phy_len > sizeof(br->phy_buf))
return -ENOMEM;
if (aligned_phy_len == br->phy_len)
return 0;
/* move EOP and bytes after EOP to the end of aligned size */
move_size = pb - pb_eop;
memmove(&br->phy_buf[aligned_phy_len - move_size], pb_eop, move_size);
/* fill the hole with PHY_IDLEs */
memset(pb_eop, PHY_IDLE, aligned_phy_len - br->phy_len);
/* update the phy data length */
br->phy_len = aligned_phy_len;
return 0;
}
/*
* In tx phase, the slave only returns PHY_IDLE (0x4a). So the driver will
* ignore rx in tx phase.
*/
static int br_do_tx(struct spi_avmm_bridge *br)
{
/* reorder words for spi transfer */
if (br->swap_words)
br->swap_words(br->phy_buf, br->phy_len);
/* send all data in phy_buf */
return spi_write(br->spi, br->phy_buf, br->phy_len);
}
/*
* This function read the rx byte stream from SPI word by word and convert
* them to transaction layer data in br->trans_buf. It also stores the length
* of rx transaction layer data in br->trans_len
*
* The slave may send an unknown number of PHY_IDLEs in rx phase, so we cannot
* prepare a fixed length buffer to receive all of the rx data in a batch. We
* have to read word by word and convert them to transaction layer data at
* once.
*/
static int br_do_rx_and_pkt_phy_parse(struct spi_avmm_bridge *br)
{
bool eop_found = false, channel_found = false, esc_found = false;
bool valid_word = false, last_try = false;
struct device *dev = &br->spi->dev;
char *pb, *tb_limit, *tb = NULL;
unsigned long poll_timeout;
int ret, i;
tb_limit = br->trans_buf + ARRAY_SIZE(br->trans_buf);
pb = br->phy_buf;
poll_timeout = jiffies + SPI_AVMM_XFER_TIMEOUT;
while (tb < tb_limit) {
ret = spi_read(br->spi, pb, br->word_len);
if (ret)
return ret;
/* reorder the word back */
if (br->swap_words)
br->swap_words(pb, br->word_len);
valid_word = false;
for (i = 0; i < br->word_len; i++) {
/* drop everything before first SOP */
if (!tb && pb[i] != PKT_SOP)
continue;
/* drop PHY_IDLE */
if (pb[i] == PHY_IDLE)
continue;
valid_word = true;
/*
* We don't support multiple channels, so error out if
* a non-zero channel number is found.
*/
if (channel_found) {
if (pb[i] != 0) {
dev_err(dev, "%s channel num != 0\n",
__func__);
return -EFAULT;
}
channel_found = false;
continue;
}
switch (pb[i]) {
case PKT_SOP:
/*
* reset the parsing if a second SOP appears.
*/
tb = br->trans_buf;
eop_found = false;
channel_found = false;
esc_found = false;
break;
case PKT_EOP:
/*
* No special char is expected after ESC char.
* No special char (except ESC & PHY_IDLE) is
* expected after EOP char.
*
* The special chars are all dropped.
*/
if (esc_found || eop_found)
return -EFAULT;
eop_found = true;
break;
case PKT_CHANNEL:
if (esc_found || eop_found)
return -EFAULT;
channel_found = true;
break;
case PKT_ESC:
case PHY_ESC:
if (esc_found)
return -EFAULT;
esc_found = true;
break;
default:
/* Record the normal byte in trans_buf. */
if (esc_found) {
*tb++ = pb[i] ^ 0x20;
esc_found = false;
} else {
*tb++ = pb[i];
}
/*
* We get the last normal byte after EOP, it is
* time we finish. Normally the function should
* return here.
*/
if (eop_found) {
br->trans_len = tb - br->trans_buf;
return 0;
}
}
}
if (valid_word) {
/* update poll timeout when we get valid word */
poll_timeout = jiffies + SPI_AVMM_XFER_TIMEOUT;
last_try = false;
} else {
/*
* We timeout when rx keeps invalid for some time. But
* it is possible we are scheduled out for long time
* after a spi_read. So when we are scheduled in, a SW
* timeout happens. But actually HW may have worked fine and
* has been ready long time ago. So we need to do an extra
* read, if we get a valid word then we could continue rx,
* otherwise real a HW issue happens.
*/
if (last_try)
return -ETIMEDOUT;
if (time_after(jiffies, poll_timeout))
last_try = true;
}
}
/*
* We have used out all transfer layer buffer but cannot find the end
* of the byte stream.
*/
dev_err(dev, "%s transfer buffer is full but rx doesn't end\n",
__func__);
return -EFAULT;
}
/*
* For read transactions, the avmm bus will directly return register values
* without transaction response header.
*/
static int br_rd_trans_rx_parse(struct spi_avmm_bridge *br,
u32 *val, unsigned int expected_count)
{
unsigned int i, trans_len = br->trans_len;
__le32 *data;
if (expected_count * SPI_AVMM_VAL_SIZE != trans_len)
return -EFAULT;
data = (__le32 *)br->trans_buf;
for (i = 0; i < expected_count; i++)
*val++ = le32_to_cpu(*data++);
return 0;
}
/*
* For write transactions, the slave will return a transaction response
* header.
*/
static int br_wr_trans_rx_parse(struct spi_avmm_bridge *br,
unsigned int expected_count)
{
unsigned int trans_len = br->trans_len;
struct trans_resp_header *resp;
u8 code;
u16 val_len;
if (trans_len != TRANS_RESP_HD_SIZE)
return -EFAULT;
resp = (struct trans_resp_header *)br->trans_buf;
code = resp->r_code ^ 0x80;
val_len = be16_to_cpu(resp->size);
if (!val_len || val_len != expected_count * SPI_AVMM_VAL_SIZE)
return -EFAULT;
/* error out if the trans code doesn't align with the val size */
if ((val_len == SPI_AVMM_VAL_SIZE && code != TRANS_CODE_WRITE) ||
(val_len > SPI_AVMM_VAL_SIZE && code != TRANS_CODE_SEQ_WRITE))
return -EFAULT;
return 0;
}
static int do_reg_access(void *context, bool is_read, unsigned int reg,
unsigned int *value, unsigned int count)
{
struct spi_avmm_bridge *br = context;
int ret;
/* invalidate bridge buffers first */
br->trans_len = 0;
br->phy_len = 0;
ret = br_trans_tx_prepare(br, is_read, reg, value, count);
if (ret)
return ret;
ret = br_pkt_phy_tx_prepare(br);
if (ret)
return ret;
ret = br_do_tx(br);
if (ret)
return ret;
ret = br_do_rx_and_pkt_phy_parse(br);
if (ret)
return ret;
if (is_read)
return br_rd_trans_rx_parse(br, value, count);
else
return br_wr_trans_rx_parse(br, count);
}
static int regmap_spi_avmm_gather_write(void *context,
const void *reg_buf, size_t reg_len,
const void *val_buf, size_t val_len)
{
if (reg_len != SPI_AVMM_REG_SIZE)
return -EINVAL;
if (!IS_ALIGNED(val_len, SPI_AVMM_VAL_SIZE))
return -EINVAL;
return do_reg_access(context, false, *(u32 *)reg_buf, (u32 *)val_buf,
val_len / SPI_AVMM_VAL_SIZE);
}
static int regmap_spi_avmm_write(void *context, const void *data, size_t bytes)
{
if (bytes < SPI_AVMM_REG_SIZE + SPI_AVMM_VAL_SIZE)
return -EINVAL;
return regmap_spi_avmm_gather_write(context, data, SPI_AVMM_REG_SIZE,
data + SPI_AVMM_REG_SIZE,
bytes - SPI_AVMM_REG_SIZE);
}
static int regmap_spi_avmm_read(void *context,
const void *reg_buf, size_t reg_len,
void *val_buf, size_t val_len)
{
if (reg_len != SPI_AVMM_REG_SIZE)
return -EINVAL;
if (!IS_ALIGNED(val_len, SPI_AVMM_VAL_SIZE))
return -EINVAL;
return do_reg_access(context, true, *(u32 *)reg_buf, val_buf,
(val_len / SPI_AVMM_VAL_SIZE));
}
static struct spi_avmm_bridge *
spi_avmm_bridge_ctx_gen(struct spi_device *spi)
{
struct spi_avmm_bridge *br;
if (!spi)
return ERR_PTR(-ENODEV);
/* Only support BPW == 8 or 32 now. Try 32 BPW first. */
spi->mode = SPI_MODE_1;
spi->bits_per_word = 32;
if (spi_setup(spi)) {
spi->bits_per_word = 8;
if (spi_setup(spi))
return ERR_PTR(-EINVAL);
}
br = kzalloc(sizeof(*br), GFP_KERNEL);
if (!br)
return ERR_PTR(-ENOMEM);
br->spi = spi;
br->word_len = spi->bits_per_word / 8;
if (br->word_len == 4) {
/*
* The protocol requires little endian byte order but MSB
* first. So driver needs to swap the byte order word by word
* if word length > 1.
*/
br->swap_words = br_swap_words_32;
}
return br;
}
static void spi_avmm_bridge_ctx_free(void *context)
{
kfree(context);
}
static const struct regmap_bus regmap_spi_avmm_bus = {
.write = regmap_spi_avmm_write,
.gather_write = regmap_spi_avmm_gather_write,
.read = regmap_spi_avmm_read,
.reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
.val_format_endian_default = REGMAP_ENDIAN_NATIVE,
.max_raw_read = SPI_AVMM_VAL_SIZE * MAX_READ_CNT,
.max_raw_write = SPI_AVMM_VAL_SIZE * MAX_WRITE_CNT,
.free_context = spi_avmm_bridge_ctx_free,
};
struct regmap *__regmap_init_spi_avmm(struct spi_device *spi,
const struct regmap_config *config,
struct lock_class_key *lock_key,
const char *lock_name)
{
struct spi_avmm_bridge *bridge;
struct regmap *map;
bridge = spi_avmm_bridge_ctx_gen(spi);
if (IS_ERR(bridge))
return ERR_CAST(bridge);
map = __regmap_init(&spi->dev, &regmap_spi_avmm_bus,
bridge, config, lock_key, lock_name);
if (IS_ERR(map)) {
spi_avmm_bridge_ctx_free(bridge);
return ERR_CAST(map);
}
return map;
}
EXPORT_SYMBOL_GPL(__regmap_init_spi_avmm);
struct regmap *__devm_regmap_init_spi_avmm(struct spi_device *spi,
const struct regmap_config *config,
struct lock_class_key *lock_key,
const char *lock_name)
{
struct spi_avmm_bridge *bridge;
struct regmap *map;
bridge = spi_avmm_bridge_ctx_gen(spi);
if (IS_ERR(bridge))
return ERR_CAST(bridge);
map = __devm_regmap_init(&spi->dev, &regmap_spi_avmm_bus,
bridge, config, lock_key, lock_name);
if (IS_ERR(map)) {
spi_avmm_bridge_ctx_free(bridge);
return ERR_CAST(map);
}
return map;
}
EXPORT_SYMBOL_GPL(__devm_regmap_init_spi_avmm);
MODULE_LICENSE("GPL v2");