/* * 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 #include #include #include #include #include #include #include /* 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 /* * We must get a response from the EC in 5ms. This is a very long * time, but the flash write command can take 2-3ms. The EC command * processing is currently not very fast (about 500us). We could * look at speeding this up and making the flash write command a * 'slow' command, requiring a GET_STATUS wait loop, like flash * erase. */ #define EC_MSG_DEADLINE_MS 5 /* * 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. It seems * that 50us is enough with the 16MHz STM32 EC. */ #define EC_SPI_RECOVERY_TIME_NS (50 * 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 */ struct cros_ec_spi { struct spi_device *spi; s64 last_transfer_ns; }; 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++) dev_cont(dev, " %02x", ptr[i]); #endif } /** * 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) { struct cros_ec_spi *ec_spi = ec_dev->priv; struct spi_transfer trans; struct spi_message msg; u8 *ptr, *end; int ret; unsigned long deadline; int todo; /* Receive data until we see the header byte */ deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS); do { memset(&trans, '\0', sizeof(trans)); trans.cs_change = 1; trans.rx_buf = ptr = ec_dev->din; trans.len = EC_MSG_PREAMBLE_COUNT; spi_message_init(&msg); spi_message_add_tail(&trans, &msg); ret = spi_sync(ec_spi->spi, &msg); if (ret < 0) { dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); return ret; } for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) { if (*ptr == EC_MSG_HEADER) { dev_dbg(ec_dev->dev, "msg found at %zd\n", ptr - ec_dev->din); break; } } if (time_after(jiffies, deadline)) { dev_warn(ec_dev->dev, "EC failed to respond in time\n"); return -ETIMEDOUT; } } while (ptr == end); /* * 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); memset(&trans, '\0', sizeof(trans)); trans.cs_change = 1; trans.rx_buf = ptr; trans.len = todo; spi_message_init(&msg); spi_message_add_tail(&trans, &msg); /* send command to EC and read answer */ BUG_ON((u8 *)trans.rx_buf - ec_dev->din + todo > ec_dev->din_size); ret = spi_sync(ec_spi->spi, &msg); if (ret < 0) { dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); 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_command_spi_xfer - Transfer a message over SPI and receive the reply * * @ec_dev: ChromeOS EC device * @ec_msg: Message to transfer */ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, struct cros_ec_msg *ec_msg) { struct cros_ec_spi *ec_spi = ec_dev->priv; struct spi_transfer trans; struct spi_message msg; int i, len; u8 *ptr; int sum; int ret = 0, final_ret; struct timespec ts; 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) { struct timespec ts; unsigned long delay; /* The delay completed so far */ ktime_get_ts(&ts); delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns; if (delay < EC_SPI_RECOVERY_TIME_NS) ndelay(delay); } /* 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.len = len; trans.cs_change = 1; spi_message_init(&msg); spi_message_add_tail(&trans, &msg); ret = spi_sync(ec_spi->spi, &msg); /* Get the response */ if (!ret) { ret = cros_ec_spi_receive_response(ec_dev, ec_msg->in_len + EC_MSG_TX_PROTO_BYTES); } else { dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); } /* turn off CS */ spi_message_init(&msg); final_ret = spi_sync(ec_spi->spi, &msg); ktime_get_ts(&ts); ec_spi->last_transfer_ns = timespec_to_ns(&ts); if (!ret) ret = final_ret; if (ret < 0) { dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); return ret; } /* check response error code */ ptr = ec_dev->din; if (ptr[0]) { dev_warn(ec_dev->dev, "command 0x%02x returned an error %d\n", ec_msg->cmd, ptr[0]); debug_packet(ec_dev->dev, "in_err", ptr, len); return -EINVAL; } len = ptr[1]; sum = ptr[0] + ptr[1]; if (len > ec_msg->in_len) { dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)", len, ec_msg->in_len); return -ENOSPC; } /* copy response packet payload and compute checksum */ for (i = 0; i < len; i++) { sum += ptr[i + 2]; if (ec_msg->in_len) ec_msg->in_buf[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]); return -EBADMSG; } return 0; } static int cros_ec_probe_spi(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; spi_set_drvdata(spi, ec_dev); ec_dev->name = "SPI"; ec_dev->dev = dev; ec_dev->priv = ec_spi; ec_dev->irq = spi->irq; ec_dev->command_xfer = cros_ec_command_spi_xfer; ec_dev->ec_name = ec_spi->spi->modalias; ec_dev->phys_name = dev_name(&ec_spi->spi->dev); ec_dev->parent = &ec_spi->spi->dev; ec_dev->din_size = EC_MSG_BYTES + EC_MSG_PREAMBLE_COUNT; ec_dev->dout_size = EC_MSG_BYTES; err = cros_ec_register(ec_dev); if (err) { dev_err(dev, "cannot register EC\n"); return err; } return 0; } static int cros_ec_remove_spi(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 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", .owner = THIS_MODULE, .pm = &cros_ec_spi_pm_ops, }, .probe = cros_ec_probe_spi, .remove = cros_ec_remove_spi, .id_table = cros_ec_spi_id, }; module_spi_driver(cros_ec_driver_spi); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)");