diff options
Diffstat (limited to 'drivers/platform/chrome/cros_ec_spi.c')
| -rw-r--r-- | drivers/platform/chrome/cros_ec_spi.c | 743 |
1 files changed, 743 insertions, 0 deletions
diff --git a/drivers/platform/chrome/cros_ec_spi.c b/drivers/platform/chrome/cros_ec_spi.c new file mode 100644 index 000000000..2060d1483 --- /dev/null +++ b/drivers/platform/chrome/cros_ec_spi.c @@ -0,0 +1,743 @@ +/* + * ChromeOS EC multi-function device (SPI) + * + * Copyright (C) 2012 Google, Inc + * + * This software is licensed under the terms of the GNU General Public + * License version 2, as published by the Free Software Foundation, and + * may be copied, distributed, and modified under those terms. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <linux/delay.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/mfd/cros_ec.h> +#include <linux/mfd/cros_ec_commands.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/slab.h> +#include <linux/spi/spi.h> + + +/* The header byte, which follows the preamble */ +#define EC_MSG_HEADER 0xec + +/* + * Number of EC preamble bytes we read at a time. Since it takes + * about 400-500us for the EC to respond there is not a lot of + * point in tuning this. If the EC could respond faster then + * we could increase this so that might expect the preamble and + * message to occur in a single transaction. However, the maximum + * SPI transfer size is 256 bytes, so at 5MHz we need a response + * time of perhaps <320us (200 bytes / 1600 bits). + */ +#define EC_MSG_PREAMBLE_COUNT 32 + +/* + * Allow for a long time for the EC to respond. We support i2c + * tunneling and support fairly long messages for the tunnel (249 + * bytes long at the moment). If we're talking to a 100 kHz device + * on the other end and need to transfer ~256 bytes, then we need: + * 10 us/bit * ~10 bits/byte * ~256 bytes = ~25ms + * + * We'll wait 8 times that to handle clock stretching and other + * paranoia. Note that some battery gas gauge ICs claim to have a + * clock stretch of 144ms in rare situations. That's incentive for + * not directly passing i2c through, but it's too late for that for + * existing hardware. + * + * It's pretty unlikely that we'll really see a 249 byte tunnel in + * anything other than testing. If this was more common we might + * consider having slow commands like this require a GET_STATUS + * wait loop. The 'flash write' command would be another candidate + * for this, clocking in at 2-3ms. + */ +#define EC_MSG_DEADLINE_MS 200 + +/* + * Time between raising the SPI chip select (for the end of a + * transaction) and dropping it again (for the next transaction). + * If we go too fast, the EC will miss the transaction. We know that we + * need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be + * safe. + */ +#define EC_SPI_RECOVERY_TIME_NS (200 * 1000) + +/** + * struct cros_ec_spi - information about a SPI-connected EC + * + * @spi: SPI device we are connected to + * @last_transfer_ns: time that we last finished a transfer. + * @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that + * is sent when we want to turn on CS at the start of a transaction. + * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that + * is sent when we want to turn off CS at the end of a transaction. + */ +struct cros_ec_spi { + struct spi_device *spi; + s64 last_transfer_ns; + unsigned int start_of_msg_delay; + unsigned int end_of_msg_delay; +}; + +static void debug_packet(struct device *dev, const char *name, u8 *ptr, + int len) +{ +#ifdef DEBUG + int i; + + dev_dbg(dev, "%s: ", name); + for (i = 0; i < len; i++) + pr_cont(" %02x", ptr[i]); + + pr_cont("\n"); +#endif +} + +static int terminate_request(struct cros_ec_device *ec_dev) +{ + struct cros_ec_spi *ec_spi = ec_dev->priv; + struct spi_message msg; + struct spi_transfer trans; + int ret; + + /* + * Turn off CS, possibly adding a delay to ensure the rising edge + * doesn't come too soon after the end of the data. + */ + spi_message_init(&msg); + memset(&trans, 0, sizeof(trans)); + trans.delay_usecs = ec_spi->end_of_msg_delay; + spi_message_add_tail(&trans, &msg); + + ret = spi_sync_locked(ec_spi->spi, &msg); + + /* Reset end-of-response timer */ + ec_spi->last_transfer_ns = ktime_get_ns(); + if (ret < 0) { + dev_err(ec_dev->dev, + "cs-deassert spi transfer failed: %d\n", + ret); + } + + return ret; +} + +/** + * receive_n_bytes - receive n bytes from the EC. + * + * Assumes buf is a pointer into the ec_dev->din buffer + */ +static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n) +{ + struct cros_ec_spi *ec_spi = ec_dev->priv; + struct spi_transfer trans; + struct spi_message msg; + int ret; + + BUG_ON(buf - ec_dev->din + n > ec_dev->din_size); + + memset(&trans, 0, sizeof(trans)); + trans.cs_change = 1; + trans.rx_buf = buf; + trans.len = n; + + spi_message_init(&msg); + spi_message_add_tail(&trans, &msg); + ret = spi_sync_locked(ec_spi->spi, &msg); + if (ret < 0) + dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); + + return ret; +} + +/** + * cros_ec_spi_receive_packet - Receive a packet from the EC. + * + * This function has two phases: reading the preamble bytes (since if we read + * data from the EC before it is ready to send, we just get preamble) and + * reading the actual message. + * + * The received data is placed into ec_dev->din. + * + * @ec_dev: ChromeOS EC device + * @need_len: Number of message bytes we need to read + */ +static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev, + int need_len) +{ + struct ec_host_response *response; + u8 *ptr, *end; + int ret; + unsigned long deadline; + int todo; + + BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT); + + /* Receive data until we see the header byte */ + deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS); + while (true) { + unsigned long start_jiffies = jiffies; + + ret = receive_n_bytes(ec_dev, + ec_dev->din, + EC_MSG_PREAMBLE_COUNT); + if (ret < 0) + return ret; + + ptr = ec_dev->din; + for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) { + if (*ptr == EC_SPI_FRAME_START) { + dev_dbg(ec_dev->dev, "msg found at %zd\n", + ptr - ec_dev->din); + break; + } + } + if (ptr != end) + break; + + /* + * Use the time at the start of the loop as a timeout. This + * gives us one last shot at getting the transfer and is useful + * in case we got context switched out for a while. + */ + if (time_after(start_jiffies, deadline)) { + dev_warn(ec_dev->dev, "EC failed to respond in time\n"); + return -ETIMEDOUT; + } + } + + /* + * ptr now points to the header byte. Copy any valid data to the + * start of our buffer + */ + todo = end - ++ptr; + BUG_ON(todo < 0 || todo > ec_dev->din_size); + todo = min(todo, need_len); + memmove(ec_dev->din, ptr, todo); + ptr = ec_dev->din + todo; + dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n", + need_len, todo); + need_len -= todo; + + /* If the entire response struct wasn't read, get the rest of it. */ + if (todo < sizeof(*response)) { + ret = receive_n_bytes(ec_dev, ptr, sizeof(*response) - todo); + if (ret < 0) + return -EBADMSG; + ptr += (sizeof(*response) - todo); + todo = sizeof(*response); + } + + response = (struct ec_host_response *)ec_dev->din; + + /* Abort if data_len is too large. */ + if (response->data_len > ec_dev->din_size) + return -EMSGSIZE; + + /* Receive data until we have it all */ + while (need_len > 0) { + /* + * We can't support transfers larger than the SPI FIFO size + * unless we have DMA. We don't have DMA on the ISP SPI ports + * for Exynos. We need a way of asking SPI driver for + * maximum-supported transfer size. + */ + todo = min(need_len, 256); + dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n", + todo, need_len, ptr - ec_dev->din); + + ret = receive_n_bytes(ec_dev, ptr, todo); + if (ret < 0) + return ret; + + ptr += todo; + need_len -= todo; + } + + dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din); + + return 0; +} + +/** + * cros_ec_spi_receive_response - Receive a response from the EC. + * + * This function has two phases: reading the preamble bytes (since if we read + * data from the EC before it is ready to send, we just get preamble) and + * reading the actual message. + * + * The received data is placed into ec_dev->din. + * + * @ec_dev: ChromeOS EC device + * @need_len: Number of message bytes we need to read + */ +static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev, + int need_len) +{ + u8 *ptr, *end; + int ret; + unsigned long deadline; + int todo; + + BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT); + + /* Receive data until we see the header byte */ + deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS); + while (true) { + unsigned long start_jiffies = jiffies; + + ret = receive_n_bytes(ec_dev, + ec_dev->din, + EC_MSG_PREAMBLE_COUNT); + if (ret < 0) + return ret; + + ptr = ec_dev->din; + for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) { + if (*ptr == EC_SPI_FRAME_START) { + dev_dbg(ec_dev->dev, "msg found at %zd\n", + ptr - ec_dev->din); + break; + } + } + if (ptr != end) + break; + + /* + * Use the time at the start of the loop as a timeout. This + * gives us one last shot at getting the transfer and is useful + * in case we got context switched out for a while. + */ + if (time_after(start_jiffies, deadline)) { + dev_warn(ec_dev->dev, "EC failed to respond in time\n"); + return -ETIMEDOUT; + } + } + + /* + * ptr now points to the header byte. Copy any valid data to the + * start of our buffer + */ + todo = end - ++ptr; + BUG_ON(todo < 0 || todo > ec_dev->din_size); + todo = min(todo, need_len); + memmove(ec_dev->din, ptr, todo); + ptr = ec_dev->din + todo; + dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n", + need_len, todo); + need_len -= todo; + + /* Receive data until we have it all */ + while (need_len > 0) { + /* + * We can't support transfers larger than the SPI FIFO size + * unless we have DMA. We don't have DMA on the ISP SPI ports + * for Exynos. We need a way of asking SPI driver for + * maximum-supported transfer size. + */ + todo = min(need_len, 256); + dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n", + todo, need_len, ptr - ec_dev->din); + + ret = receive_n_bytes(ec_dev, ptr, todo); + if (ret < 0) + return ret; + + debug_packet(ec_dev->dev, "interim", ptr, todo); + ptr += todo; + need_len -= todo; + } + + dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din); + + return 0; +} + +/** + * cros_ec_pkt_xfer_spi - Transfer a packet over SPI and receive the reply + * + * @ec_dev: ChromeOS EC device + * @ec_msg: Message to transfer + */ +static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev, + struct cros_ec_command *ec_msg) +{ + struct ec_host_response *response; + struct cros_ec_spi *ec_spi = ec_dev->priv; + struct spi_transfer trans, trans_delay; + struct spi_message msg; + int i, len; + u8 *ptr; + u8 *rx_buf; + u8 sum; + u8 rx_byte; + int ret = 0, final_ret; + unsigned long delay; + + len = cros_ec_prepare_tx(ec_dev, ec_msg); + dev_dbg(ec_dev->dev, "prepared, len=%d\n", len); + + /* If it's too soon to do another transaction, wait */ + delay = ktime_get_ns() - ec_spi->last_transfer_ns; + if (delay < EC_SPI_RECOVERY_TIME_NS) + ndelay(EC_SPI_RECOVERY_TIME_NS - delay); + + rx_buf = kzalloc(len, GFP_KERNEL); + if (!rx_buf) + return -ENOMEM; + + spi_bus_lock(ec_spi->spi->master); + + /* + * Leave a gap between CS assertion and clocking of data to allow the + * EC time to wakeup. + */ + spi_message_init(&msg); + if (ec_spi->start_of_msg_delay) { + memset(&trans_delay, 0, sizeof(trans_delay)); + trans_delay.delay_usecs = ec_spi->start_of_msg_delay; + spi_message_add_tail(&trans_delay, &msg); + } + + /* Transmit phase - send our message */ + memset(&trans, 0, sizeof(trans)); + trans.tx_buf = ec_dev->dout; + trans.rx_buf = rx_buf; + trans.len = len; + trans.cs_change = 1; + spi_message_add_tail(&trans, &msg); + ret = spi_sync_locked(ec_spi->spi, &msg); + + /* Get the response */ + if (!ret) { + /* Verify that EC can process command */ + for (i = 0; i < len; i++) { + rx_byte = rx_buf[i]; + /* + * Seeing the PAST_END, RX_BAD_DATA, or NOT_READY + * markers are all signs that the EC didn't fully + * receive our command. e.g., if the EC is flashing + * itself, it can't respond to any commands and instead + * clocks out EC_SPI_PAST_END from its SPI hardware + * buffer. Similar occurrences can happen if the AP is + * too slow to clock out data after asserting CS -- the + * EC will abort and fill its buffer with + * EC_SPI_RX_BAD_DATA. + * + * In all cases, these errors should be safe to retry. + * Report -EAGAIN and let the caller decide what to do + * about that. + */ + if (rx_byte == EC_SPI_PAST_END || + rx_byte == EC_SPI_RX_BAD_DATA || + rx_byte == EC_SPI_NOT_READY) { + ret = -EAGAIN; + break; + } + } + } + + if (!ret) + ret = cros_ec_spi_receive_packet(ec_dev, + ec_msg->insize + sizeof(*response)); + else if (ret != -EAGAIN) + dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); + + final_ret = terminate_request(ec_dev); + + spi_bus_unlock(ec_spi->spi->master); + + if (!ret) + ret = final_ret; + if (ret < 0) + goto exit; + + ptr = ec_dev->din; + + /* check response error code */ + response = (struct ec_host_response *)ptr; + ec_msg->result = response->result; + + ret = cros_ec_check_result(ec_dev, ec_msg); + if (ret) + goto exit; + + len = response->data_len; + sum = 0; + if (len > ec_msg->insize) { + dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)", + len, ec_msg->insize); + ret = -EMSGSIZE; + goto exit; + } + + for (i = 0; i < sizeof(*response); i++) + sum += ptr[i]; + + /* copy response packet payload and compute checksum */ + memcpy(ec_msg->data, ptr + sizeof(*response), len); + for (i = 0; i < len; i++) + sum += ec_msg->data[i]; + + if (sum) { + dev_err(ec_dev->dev, + "bad packet checksum, calculated %x\n", + sum); + ret = -EBADMSG; + goto exit; + } + + ret = len; +exit: + kfree(rx_buf); + if (ec_msg->command == EC_CMD_REBOOT_EC) + msleep(EC_REBOOT_DELAY_MS); + + return ret; +} + +/** + * cros_ec_cmd_xfer_spi - Transfer a message over SPI and receive the reply + * + * @ec_dev: ChromeOS EC device + * @ec_msg: Message to transfer + */ +static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev, + struct cros_ec_command *ec_msg) +{ + struct cros_ec_spi *ec_spi = ec_dev->priv; + struct spi_transfer trans; + struct spi_message msg; + int i, len; + u8 *ptr; + u8 *rx_buf; + u8 rx_byte; + int sum; + int ret = 0, final_ret; + unsigned long delay; + + len = cros_ec_prepare_tx(ec_dev, ec_msg); + dev_dbg(ec_dev->dev, "prepared, len=%d\n", len); + + /* If it's too soon to do another transaction, wait */ + delay = ktime_get_ns() - ec_spi->last_transfer_ns; + if (delay < EC_SPI_RECOVERY_TIME_NS) + ndelay(EC_SPI_RECOVERY_TIME_NS - delay); + + rx_buf = kzalloc(len, GFP_KERNEL); + if (!rx_buf) + return -ENOMEM; + + spi_bus_lock(ec_spi->spi->master); + + /* Transmit phase - send our message */ + debug_packet(ec_dev->dev, "out", ec_dev->dout, len); + memset(&trans, 0, sizeof(trans)); + trans.tx_buf = ec_dev->dout; + trans.rx_buf = rx_buf; + trans.len = len; + trans.cs_change = 1; + spi_message_init(&msg); + spi_message_add_tail(&trans, &msg); + ret = spi_sync_locked(ec_spi->spi, &msg); + + /* Get the response */ + if (!ret) { + /* Verify that EC can process command */ + for (i = 0; i < len; i++) { + rx_byte = rx_buf[i]; + /* See comments in cros_ec_pkt_xfer_spi() */ + if (rx_byte == EC_SPI_PAST_END || + rx_byte == EC_SPI_RX_BAD_DATA || + rx_byte == EC_SPI_NOT_READY) { + ret = -EAGAIN; + break; + } + } + } + + if (!ret) + ret = cros_ec_spi_receive_response(ec_dev, + ec_msg->insize + EC_MSG_TX_PROTO_BYTES); + else if (ret != -EAGAIN) + dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); + + final_ret = terminate_request(ec_dev); + + spi_bus_unlock(ec_spi->spi->master); + + if (!ret) + ret = final_ret; + if (ret < 0) + goto exit; + + ptr = ec_dev->din; + + /* check response error code */ + ec_msg->result = ptr[0]; + ret = cros_ec_check_result(ec_dev, ec_msg); + if (ret) + goto exit; + + len = ptr[1]; + sum = ptr[0] + ptr[1]; + if (len > ec_msg->insize) { + dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)", + len, ec_msg->insize); + ret = -ENOSPC; + goto exit; + } + + /* copy response packet payload and compute checksum */ + for (i = 0; i < len; i++) { + sum += ptr[i + 2]; + if (ec_msg->insize) + ec_msg->data[i] = ptr[i + 2]; + } + sum &= 0xff; + + debug_packet(ec_dev->dev, "in", ptr, len + 3); + + if (sum != ptr[len + 2]) { + dev_err(ec_dev->dev, + "bad packet checksum, expected %02x, got %02x\n", + sum, ptr[len + 2]); + ret = -EBADMSG; + goto exit; + } + + ret = len; +exit: + kfree(rx_buf); + if (ec_msg->command == EC_CMD_REBOOT_EC) + msleep(EC_REBOOT_DELAY_MS); + + return ret; +} + +static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev) +{ + struct device_node *np = dev->of_node; + u32 val; + int ret; + + ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val); + if (!ret) + ec_spi->start_of_msg_delay = val; + + ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val); + if (!ret) + ec_spi->end_of_msg_delay = val; +} + +static int cros_ec_spi_probe(struct spi_device *spi) +{ + struct device *dev = &spi->dev; + struct cros_ec_device *ec_dev; + struct cros_ec_spi *ec_spi; + int err; + + spi->bits_per_word = 8; + spi->mode = SPI_MODE_0; + err = spi_setup(spi); + if (err < 0) + return err; + + ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL); + if (ec_spi == NULL) + return -ENOMEM; + ec_spi->spi = spi; + ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL); + if (!ec_dev) + return -ENOMEM; + + /* Check for any DT properties */ + cros_ec_spi_dt_probe(ec_spi, dev); + + spi_set_drvdata(spi, ec_dev); + ec_dev->dev = dev; + ec_dev->priv = ec_spi; + ec_dev->irq = spi->irq; + ec_dev->cmd_xfer = cros_ec_cmd_xfer_spi; + ec_dev->pkt_xfer = cros_ec_pkt_xfer_spi; + ec_dev->phys_name = dev_name(&ec_spi->spi->dev); + ec_dev->din_size = EC_MSG_PREAMBLE_COUNT + + sizeof(struct ec_host_response) + + sizeof(struct ec_response_get_protocol_info); + ec_dev->dout_size = sizeof(struct ec_host_request); + + ec_spi->last_transfer_ns = ktime_get_ns(); + + err = cros_ec_register(ec_dev); + if (err) { + dev_err(dev, "cannot register EC\n"); + return err; + } + + device_init_wakeup(&spi->dev, true); + + return 0; +} + +static int cros_ec_spi_remove(struct spi_device *spi) +{ + struct cros_ec_device *ec_dev; + + ec_dev = spi_get_drvdata(spi); + cros_ec_remove(ec_dev); + + return 0; +} + +#ifdef CONFIG_PM_SLEEP +static int cros_ec_spi_suspend(struct device *dev) +{ + struct cros_ec_device *ec_dev = dev_get_drvdata(dev); + + return cros_ec_suspend(ec_dev); +} + +static int cros_ec_spi_resume(struct device *dev) +{ + struct cros_ec_device *ec_dev = dev_get_drvdata(dev); + + return cros_ec_resume(ec_dev); +} +#endif + +static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend, + cros_ec_spi_resume); + +static const struct of_device_id cros_ec_spi_of_match[] = { + { .compatible = "google,cros-ec-spi", }, + { /* sentinel */ }, +}; +MODULE_DEVICE_TABLE(of, cros_ec_spi_of_match); + +static const struct spi_device_id cros_ec_spi_id[] = { + { "cros-ec-spi", 0 }, + { } +}; +MODULE_DEVICE_TABLE(spi, cros_ec_spi_id); + +static struct spi_driver cros_ec_driver_spi = { + .driver = { + .name = "cros-ec-spi", + .of_match_table = of_match_ptr(cros_ec_spi_of_match), + .pm = &cros_ec_spi_pm_ops, + }, + .probe = cros_ec_spi_probe, + .remove = cros_ec_spi_remove, + .id_table = cros_ec_spi_id, +}; + +module_spi_driver(cros_ec_driver_spi); + +MODULE_LICENSE("GPL v2"); +MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)"); 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