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path: root/drivers/spi/spi-bcm2835aux.c
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Diffstat (limited to 'drivers/spi/spi-bcm2835aux.c')
-rw-r--r--drivers/spi/spi-bcm2835aux.c512
1 files changed, 512 insertions, 0 deletions
diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
new file mode 100644
index 000000000000..7de6f8472a81
--- /dev/null
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -0,0 +1,512 @@
+/*
+ * Driver for Broadcom BCM2835 auxiliary SPI Controllers
+ *
+ * the driver does not rely on the native chipselects at all
+ * but only uses the gpio type chipselects
+ *
+ * Based on: spi-bcm2835.c
+ *
+ * Copyright (C) 2015 Martin Sperl
+ *
+ * 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/clk.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/of_gpio.h>
+#include <linux/of_irq.h>
+#include <linux/regmap.h>
+#include <linux/spi/spi.h>
+#include <linux/spinlock.h>
+
+/*
+ * spi register defines
+ *
+ * note there is garbage in the "official" documentation,
+ * so some data is taken from the file:
+ * brcm_usrlib/dag/vmcsx/vcinclude/bcm2708_chip/aux_io.h
+ * inside of:
+ * http://www.broadcom.com/docs/support/videocore/Brcm_Android_ICS_Graphics_Stack.tar.gz
+ */
+
+/* SPI register offsets */
+#define BCM2835_AUX_SPI_CNTL0 0x00
+#define BCM2835_AUX_SPI_CNTL1 0x04
+#define BCM2835_AUX_SPI_STAT 0x08
+#define BCM2835_AUX_SPI_PEEK 0x0C
+#define BCM2835_AUX_SPI_IO 0x20
+#define BCM2835_AUX_SPI_TXHOLD 0x30
+
+/* Bitfields in CNTL0 */
+#define BCM2835_AUX_SPI_CNTL0_SPEED 0xFFF00000
+#define BCM2835_AUX_SPI_CNTL0_SPEED_MAX 0xFFF
+#define BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT 20
+#define BCM2835_AUX_SPI_CNTL0_CS 0x000E0000
+#define BCM2835_AUX_SPI_CNTL0_POSTINPUT 0x00010000
+#define BCM2835_AUX_SPI_CNTL0_VAR_CS 0x00008000
+#define BCM2835_AUX_SPI_CNTL0_VAR_WIDTH 0x00004000
+#define BCM2835_AUX_SPI_CNTL0_DOUTHOLD 0x00003000
+#define BCM2835_AUX_SPI_CNTL0_ENABLE 0x00000800
+#define BCM2835_AUX_SPI_CNTL0_CPHA_IN 0x00000400
+#define BCM2835_AUX_SPI_CNTL0_CLEARFIFO 0x00000200
+#define BCM2835_AUX_SPI_CNTL0_CPHA_OUT 0x00000100
+#define BCM2835_AUX_SPI_CNTL0_CPOL 0x00000080
+#define BCM2835_AUX_SPI_CNTL0_MSBF_OUT 0x00000040
+#define BCM2835_AUX_SPI_CNTL0_SHIFTLEN 0x0000003F
+
+/* Bitfields in CNTL1 */
+#define BCM2835_AUX_SPI_CNTL1_CSHIGH 0x00000700
+#define BCM2835_AUX_SPI_CNTL1_IDLE 0x00000080
+#define BCM2835_AUX_SPI_CNTL1_TXEMPTY 0x00000040
+#define BCM2835_AUX_SPI_CNTL1_MSBF_IN 0x00000002
+#define BCM2835_AUX_SPI_CNTL1_KEEP_IN 0x00000001
+
+/* Bitfields in STAT */
+#define BCM2835_AUX_SPI_STAT_TX_LVL 0xFF000000
+#define BCM2835_AUX_SPI_STAT_RX_LVL 0x00FF0000
+#define BCM2835_AUX_SPI_STAT_TX_FULL 0x00000400
+#define BCM2835_AUX_SPI_STAT_TX_EMPTY 0x00000200
+#define BCM2835_AUX_SPI_STAT_RX_FULL 0x00000100
+#define BCM2835_AUX_SPI_STAT_RX_EMPTY 0x00000080
+#define BCM2835_AUX_SPI_STAT_BUSY 0x00000040
+#define BCM2835_AUX_SPI_STAT_BITCOUNT 0x0000003F
+
+/* timeout values */
+#define BCM2835_AUX_SPI_POLLING_LIMIT_US 30
+#define BCM2835_AUX_SPI_POLLING_JIFFIES 2
+
+#define BCM2835_AUX_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \
+ | SPI_NO_CS)
+
+struct bcm2835aux_spi {
+ void __iomem *regs;
+ struct clk *clk;
+ int irq;
+ u32 cntl[2];
+ const u8 *tx_buf;
+ u8 *rx_buf;
+ int tx_len;
+ int rx_len;
+ int pending;
+};
+
+static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned reg)
+{
+ return readl(bs->regs + reg);
+}
+
+static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned reg,
+ u32 val)
+{
+ writel(val, bs->regs + reg);
+}
+
+static inline void bcm2835aux_rd_fifo(struct bcm2835aux_spi *bs)
+{
+ u32 data;
+ int count = min(bs->rx_len, 3);
+
+ data = bcm2835aux_rd(bs, BCM2835_AUX_SPI_IO);
+ if (bs->rx_buf) {
+ switch (count) {
+ case 4:
+ *bs->rx_buf++ = (data >> 24) & 0xff;
+ /* fallthrough */
+ case 3:
+ *bs->rx_buf++ = (data >> 16) & 0xff;
+ /* fallthrough */
+ case 2:
+ *bs->rx_buf++ = (data >> 8) & 0xff;
+ /* fallthrough */
+ case 1:
+ *bs->rx_buf++ = (data >> 0) & 0xff;
+ /* fallthrough - no default */
+ }
+ }
+ bs->rx_len -= count;
+ bs->pending -= count;
+}
+
+static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs)
+{
+ u32 data;
+ u8 byte;
+ int count;
+ int i;
+
+ /* gather up to 3 bytes to write to the FIFO */
+ count = min(bs->tx_len, 3);
+ data = 0;
+ for (i = 0; i < count; i++) {
+ byte = bs->tx_buf ? *bs->tx_buf++ : 0;
+ data |= byte << (8 * (2 - i));
+ }
+
+ /* and set the variable bit-length */
+ data |= (count * 8) << 24;
+
+ /* and decrement length */
+ bs->tx_len -= count;
+ bs->pending += count;
+
+ /* write to the correct TX-register */
+ if (bs->tx_len)
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_TXHOLD, data);
+ else
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_IO, data);
+}
+
+static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs)
+{
+ /* disable spi clearing fifo and interrupts */
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, 0);
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0,
+ BCM2835_AUX_SPI_CNTL0_CLEARFIFO);
+}
+
+static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id)
+{
+ struct spi_master *master = dev_id;
+ struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
+ irqreturn_t ret = IRQ_NONE;
+
+ /* check if we have data to read */
+ while (bs->rx_len &&
+ (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
+ BCM2835_AUX_SPI_STAT_RX_EMPTY))) {
+ bcm2835aux_rd_fifo(bs);
+ ret = IRQ_HANDLED;
+ }
+
+ /* check if we have data to write */
+ while (bs->tx_len &&
+ (bs->pending < 12) &&
+ (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
+ BCM2835_AUX_SPI_STAT_TX_FULL))) {
+ bcm2835aux_wr_fifo(bs);
+ ret = IRQ_HANDLED;
+ }
+
+ /* and check if we have reached "done" */
+ while (bs->rx_len &&
+ (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
+ BCM2835_AUX_SPI_STAT_BUSY))) {
+ bcm2835aux_rd_fifo(bs);
+ ret = IRQ_HANDLED;
+ }
+
+ /* and if rx_len is 0 then wake up completion and disable spi */
+ if (!bs->rx_len) {
+ bcm2835aux_spi_reset_hw(bs);
+ complete(&master->xfer_completion);
+ }
+
+ /* and return */
+ return ret;
+}
+
+static int __bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
+ struct spi_device *spi,
+ struct spi_transfer *tfr)
+{
+ struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
+
+ /* enable interrupts */
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] |
+ BCM2835_AUX_SPI_CNTL1_TXEMPTY |
+ BCM2835_AUX_SPI_CNTL1_IDLE);
+
+ /* and wait for finish... */
+ return 1;
+}
+
+static int bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
+ struct spi_device *spi,
+ struct spi_transfer *tfr)
+{
+ struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
+
+ /* fill in registers and fifos before enabling interrupts */
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
+
+ /* fill in tx fifo with data before enabling interrupts */
+ while ((bs->tx_len) &&
+ (bs->pending < 12) &&
+ (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
+ BCM2835_AUX_SPI_STAT_TX_FULL))) {
+ bcm2835aux_wr_fifo(bs);
+ }
+
+ /* now run the interrupt mode */
+ return __bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
+}
+
+static int bcm2835aux_spi_transfer_one_poll(struct spi_master *master,
+ struct spi_device *spi,
+ struct spi_transfer *tfr)
+{
+ struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
+ unsigned long timeout;
+ u32 stat;
+
+ /* configure spi */
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
+ bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
+
+ /* set the timeout */
+ timeout = jiffies + BCM2835_AUX_SPI_POLLING_JIFFIES;
+
+ /* loop until finished the transfer */
+ while (bs->rx_len) {
+ /* read status */
+ stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT);
+
+ /* fill in tx fifo with remaining data */
+ if ((bs->tx_len) && (!(stat & BCM2835_AUX_SPI_STAT_TX_FULL))) {
+ bcm2835aux_wr_fifo(bs);
+ continue;
+ }
+
+ /* read data from fifo for both cases */
+ if (!(stat & BCM2835_AUX_SPI_STAT_RX_EMPTY)) {
+ bcm2835aux_rd_fifo(bs);
+ continue;
+ }
+ if (!(stat & BCM2835_AUX_SPI_STAT_BUSY)) {
+ bcm2835aux_rd_fifo(bs);
+ continue;
+ }
+
+ /* there is still data pending to read check the timeout */
+ if (bs->rx_len && time_after(jiffies, timeout)) {
+ dev_dbg_ratelimited(&spi->dev,
+ "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
+ jiffies - timeout,
+ bs->tx_len, bs->rx_len);
+ /* forward to interrupt handler */
+ return __bcm2835aux_spi_transfer_one_irq(master,
+ spi, tfr);
+ }
+ }
+
+ /* Transfer complete - reset SPI HW */
+ bcm2835aux_spi_reset_hw(bs);
+
+ /* and return without waiting for completion */
+ return 0;
+}
+
+static int bcm2835aux_spi_transfer_one(struct spi_master *master,
+ struct spi_device *spi,
+ struct spi_transfer *tfr)
+{
+ struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
+ unsigned long spi_hz, clk_hz, speed;
+ unsigned long spi_used_hz;
+ unsigned long long xfer_time_us;
+
+ /* calculate the registers to handle
+ *
+ * note that we use the variable data mode, which
+ * is not optimal for longer transfers as we waste registers
+ * resulting (potentially) in more interrupts when transferring
+ * more than 12 bytes
+ */
+ bs->cntl[0] = BCM2835_AUX_SPI_CNTL0_ENABLE |
+ BCM2835_AUX_SPI_CNTL0_VAR_WIDTH |
+ BCM2835_AUX_SPI_CNTL0_MSBF_OUT;
+ bs->cntl[1] = BCM2835_AUX_SPI_CNTL1_MSBF_IN;
+
+ /* set clock */
+ spi_hz = tfr->speed_hz;
+ clk_hz = clk_get_rate(bs->clk);
+
+ if (spi_hz >= clk_hz / 2) {
+ speed = 0;
+ } else if (spi_hz) {
+ speed = DIV_ROUND_UP(clk_hz, 2 * spi_hz) - 1;
+ if (speed > BCM2835_AUX_SPI_CNTL0_SPEED_MAX)
+ speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
+ } else { /* the slowest we can go */
+ speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
+ }
+ bs->cntl[0] |= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT;
+
+ spi_used_hz = clk_hz / (2 * (speed + 1));
+
+ /* handle all the modes */
+ if (spi->mode & SPI_CPOL)
+ bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPOL;
+ if (spi->mode & SPI_CPHA)
+ bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPHA_OUT |
+ BCM2835_AUX_SPI_CNTL0_CPHA_IN;
+
+ /* set transmit buffers and length */
+ bs->tx_buf = tfr->tx_buf;
+ bs->rx_buf = tfr->rx_buf;
+ bs->tx_len = tfr->len;
+ bs->rx_len = tfr->len;
+ bs->pending = 0;
+
+ /* calculate the estimated time in us the transfer runs
+ * note that there are are 2 idle clocks after each
+ * chunk getting transferred - in our case the chunk size
+ * is 3 bytes, so we approximate this by 9 bits/byte
+ */
+ xfer_time_us = tfr->len * 9 * 1000000;
+ do_div(xfer_time_us, spi_used_hz);
+
+ /* run in polling mode for short transfers */
+ if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)
+ return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
+
+ /* run in interrupt mode for all others */
+ return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
+}
+
+static void bcm2835aux_spi_handle_err(struct spi_master *master,
+ struct spi_message *msg)
+{
+ struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
+
+ bcm2835aux_spi_reset_hw(bs);
+}
+
+static int bcm2835aux_spi_probe(struct platform_device *pdev)
+{
+ struct spi_master *master;
+ struct bcm2835aux_spi *bs;
+ struct resource *res;
+ unsigned long clk_hz;
+ int err;
+
+ master = spi_alloc_master(&pdev->dev, sizeof(*bs));
+ if (!master) {
+ dev_err(&pdev->dev, "spi_alloc_master() failed\n");
+ return -ENOMEM;
+ }
+
+ platform_set_drvdata(pdev, master);
+ master->mode_bits = BCM2835_AUX_SPI_MODE_BITS;
+ master->bits_per_word_mask = SPI_BPW_MASK(8);
+ master->num_chipselect = -1;
+ master->transfer_one = bcm2835aux_spi_transfer_one;
+ master->handle_err = bcm2835aux_spi_handle_err;
+ master->dev.of_node = pdev->dev.of_node;
+
+ bs = spi_master_get_devdata(master);
+
+ /* the main area */
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ bs->regs = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(bs->regs)) {
+ err = PTR_ERR(bs->regs);
+ goto out_master_put;
+ }
+
+ bs->clk = devm_clk_get(&pdev->dev, NULL);
+ if ((!bs->clk) || (IS_ERR(bs->clk))) {
+ err = PTR_ERR(bs->clk);
+ dev_err(&pdev->dev, "could not get clk: %d\n", err);
+ goto out_master_put;
+ }
+
+ bs->irq = platform_get_irq(pdev, 0);
+ if (bs->irq <= 0) {
+ dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
+ err = bs->irq ? bs->irq : -ENODEV;
+ goto out_master_put;
+ }
+
+ /* this also enables the HW block */
+ err = clk_prepare_enable(bs->clk);
+ if (err) {
+ dev_err(&pdev->dev, "could not prepare clock: %d\n", err);
+ goto out_master_put;
+ }
+
+ /* just checking if the clock returns a sane value */
+ clk_hz = clk_get_rate(bs->clk);
+ if (!clk_hz) {
+ dev_err(&pdev->dev, "clock returns 0 Hz\n");
+ err = -ENODEV;
+ goto out_clk_disable;
+ }
+
+ /* reset SPI-HW block */
+ bcm2835aux_spi_reset_hw(bs);
+
+ err = devm_request_irq(&pdev->dev, bs->irq,
+ bcm2835aux_spi_interrupt,
+ IRQF_SHARED,
+ dev_name(&pdev->dev), master);
+ if (err) {
+ dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
+ goto out_clk_disable;
+ }
+
+ err = devm_spi_register_master(&pdev->dev, master);
+ if (err) {
+ dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
+ goto out_clk_disable;
+ }
+
+ return 0;
+
+out_clk_disable:
+ clk_disable_unprepare(bs->clk);
+out_master_put:
+ spi_master_put(master);
+ return err;
+}
+
+static int bcm2835aux_spi_remove(struct platform_device *pdev)
+{
+ struct spi_master *master = platform_get_drvdata(pdev);
+ struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
+
+ bcm2835aux_spi_reset_hw(bs);
+
+ /* disable the HW block by releasing the clock */
+ clk_disable_unprepare(bs->clk);
+
+ return 0;
+}
+
+static const struct of_device_id bcm2835aux_spi_match[] = {
+ { .compatible = "brcm,bcm2835-aux-spi", },
+ {}
+};
+MODULE_DEVICE_TABLE(of, bcm2835aux_spi_match);
+
+static struct platform_driver bcm2835aux_spi_driver = {
+ .driver = {
+ .name = "spi-bcm2835aux",
+ .of_match_table = bcm2835aux_spi_match,
+ },
+ .probe = bcm2835aux_spi_probe,
+ .remove = bcm2835aux_spi_remove,
+};
+module_platform_driver(bcm2835aux_spi_driver);
+
+MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835 aux");
+MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
+MODULE_LICENSE("GPL v2");
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-03 09:18:33 +0000