v4.19.13 snapshot.
diff --git a/drivers/spi/spi-lp8841-rtc.c b/drivers/spi/spi-lp8841-rtc.c
new file mode 100644
index 0000000..faa577d
--- /dev/null
+++ b/drivers/spi/spi-lp8841-rtc.c
@@ -0,0 +1,256 @@
+/*
+ * SPI master driver for ICP DAS LP-8841 RTC
+ *
+ * Copyright (C) 2016 Sergei Ianovich
+ *
+ * based on
+ *
+ * Dallas DS1302 RTC Support
+ * Copyright (C) 2002 David McCullough
+ * Copyright (C) 2003 - 2007 Paul Mundt
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+
+#define DRIVER_NAME "spi_lp8841_rtc"
+
+#define SPI_LP8841_RTC_CE 0x01
+#define SPI_LP8841_RTC_CLK 0x02
+#define SPI_LP8841_RTC_nWE 0x04
+#define SPI_LP8841_RTC_MOSI 0x08
+#define SPI_LP8841_RTC_MISO 0x01
+
+/*
+ * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI
+ * GPIO driver, this SPI driver can be replaced by a simple GPIO driver
+ * providing 3 GPIO pins.
+ */
+
+struct spi_lp8841_rtc {
+ void *iomem;
+ unsigned long state;
+};
+
+static inline void
+setsck(struct spi_lp8841_rtc *data, int is_on)
+{
+ if (is_on)
+ data->state |= SPI_LP8841_RTC_CLK;
+ else
+ data->state &= ~SPI_LP8841_RTC_CLK;
+ writeb(data->state, data->iomem);
+}
+
+static inline void
+setmosi(struct spi_lp8841_rtc *data, int is_on)
+{
+ if (is_on)
+ data->state |= SPI_LP8841_RTC_MOSI;
+ else
+ data->state &= ~SPI_LP8841_RTC_MOSI;
+ writeb(data->state, data->iomem);
+}
+
+static inline int
+getmiso(struct spi_lp8841_rtc *data)
+{
+ return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;
+}
+
+static inline u32
+bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data,
+ unsigned usecs, unsigned cpol, unsigned flags,
+ u32 word, u8 bits)
+{
+ /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */
+
+ u32 shift = 32 - bits;
+ /* clock starts at inactive polarity */
+ for (; likely(bits); bits--) {
+
+ /* setup LSB (to slave) on leading edge */
+ if ((flags & SPI_MASTER_NO_TX) == 0)
+ setmosi(data, (word & 1));
+
+ usleep_range(usecs, usecs + 1); /* T(setup) */
+
+ /* sample LSB (from slave) on trailing edge */
+ word >>= 1;
+ if ((flags & SPI_MASTER_NO_RX) == 0)
+ word |= (getmiso(data) << 31);
+
+ setsck(data, !cpol);
+ usleep_range(usecs, usecs + 1);
+
+ setsck(data, cpol);
+ }
+
+ word >>= shift;
+ return word;
+}
+
+static int
+spi_lp8841_rtc_transfer_one(struct spi_master *master,
+ struct spi_device *spi,
+ struct spi_transfer *t)
+{
+ struct spi_lp8841_rtc *data = spi_master_get_devdata(master);
+ unsigned count = t->len;
+ const u8 *tx = t->tx_buf;
+ u8 *rx = t->rx_buf;
+ u8 word = 0;
+ int ret = 0;
+
+ if (tx) {
+ data->state &= ~SPI_LP8841_RTC_nWE;
+ writeb(data->state, data->iomem);
+ while (likely(count > 0)) {
+ word = *tx++;
+ bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+ SPI_MASTER_NO_RX, word, 8);
+ count--;
+ }
+ } else if (rx) {
+ data->state |= SPI_LP8841_RTC_nWE;
+ writeb(data->state, data->iomem);
+ while (likely(count > 0)) {
+ word = bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+ SPI_MASTER_NO_TX, word, 8);
+ *rx++ = word;
+ count--;
+ }
+ } else {
+ ret = -EINVAL;
+ }
+
+ spi_finalize_current_transfer(master);
+
+ return ret;
+}
+
+static void
+spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable)
+{
+ struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master);
+
+ data->state = 0;
+ writeb(data->state, data->iomem);
+ if (enable) {
+ usleep_range(4, 5);
+ data->state |= SPI_LP8841_RTC_CE;
+ writeb(data->state, data->iomem);
+ usleep_range(4, 5);
+ }
+}
+
+static int
+spi_lp8841_rtc_setup(struct spi_device *spi)
+{
+ if ((spi->mode & SPI_CS_HIGH) == 0) {
+ dev_err(&spi->dev, "unsupported active low chip select\n");
+ return -EINVAL;
+ }
+
+ if ((spi->mode & SPI_LSB_FIRST) == 0) {
+ dev_err(&spi->dev, "unsupported MSB first mode\n");
+ return -EINVAL;
+ }
+
+ if ((spi->mode & SPI_3WIRE) == 0) {
+ dev_err(&spi->dev, "unsupported wiring. 3 wires required\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id spi_lp8841_rtc_dt_ids[] = {
+ { .compatible = "icpdas,lp8841-spi-rtc" },
+ { }
+};
+
+MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids);
+#endif
+
+static int
+spi_lp8841_rtc_probe(struct platform_device *pdev)
+{
+ int ret;
+ struct spi_master *master;
+ struct spi_lp8841_rtc *data;
+ void *iomem;
+
+ master = spi_alloc_master(&pdev->dev, sizeof(*data));
+ if (!master)
+ return -ENOMEM;
+ platform_set_drvdata(pdev, master);
+
+ master->flags = SPI_MASTER_HALF_DUPLEX;
+ master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST;
+
+ master->bus_num = pdev->id;
+ master->num_chipselect = 1;
+ master->setup = spi_lp8841_rtc_setup;
+ master->set_cs = spi_lp8841_rtc_set_cs;
+ master->transfer_one = spi_lp8841_rtc_transfer_one;
+ master->bits_per_word_mask = SPI_BPW_MASK(8);
+#ifdef CONFIG_OF
+ master->dev.of_node = pdev->dev.of_node;
+#endif
+
+ data = spi_master_get_devdata(master);
+
+ iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ data->iomem = devm_ioremap_resource(&pdev->dev, iomem);
+ ret = PTR_ERR_OR_ZERO(data->iomem);
+ if (ret) {
+ dev_err(&pdev->dev, "failed to get IO address\n");
+ goto err_put_master;
+ }
+
+ /* register with the SPI framework */
+ ret = devm_spi_register_master(&pdev->dev, master);
+ if (ret) {
+ dev_err(&pdev->dev, "cannot register spi master\n");
+ goto err_put_master;
+ }
+
+ return ret;
+
+
+err_put_master:
+ spi_master_put(master);
+
+ return ret;
+}
+
+MODULE_ALIAS("platform:" DRIVER_NAME);
+
+static struct platform_driver spi_lp8841_rtc_driver = {
+ .driver = {
+ .name = DRIVER_NAME,
+ .of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids),
+ },
+ .probe = spi_lp8841_rtc_probe,
+};
+module_platform_driver(spi_lp8841_rtc_driver);
+
+MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC");
+MODULE_AUTHOR("Sergei Ianovich");
+MODULE_LICENSE("GPL");