/* * 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 4 times that to handle clock stretching and other * paranoia. * * 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 100 /* * 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, or 0 if there * if no record * @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; int ret = 0, final_ret; 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 */ if (ec_spi->last_transfer_ns) { unsigned long delay; /* The delay completed so far */ 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++) { switch (rx_buf[i]) { case EC_SPI_PAST_END: case EC_SPI_RX_BAD_DATA: case EC_SPI_NOT_READY: ret = -EAGAIN; ec_msg->result = EC_RES_IN_PROGRESS; default: break; } if (ret) break; } if (!ret) ret = cros_ec_spi_receive_packet(ec_dev, ec_msg->insize + sizeof(*response)); } else { 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; int sum; int ret = 0, final_ret; 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 */ if (ec_spi->last_transfer_ns) { unsigned long delay; /* The delay completed so far */ 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++) { switch (rx_buf[i]) { case EC_SPI_PAST_END: case EC_SPI_RX_BAD_DATA: case EC_SPI_NOT_READY: ret = -EAGAIN; ec_msg->result = EC_RES_IN_PROGRESS; default: break; } if (ret) break; } if (!ret) ret = cros_ec_spi_receive_response(ec_dev, ec_msg->insize + EC_MSG_TX_PROTO_BYTES); } else { 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); 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)");