Hello,
This is the second version of driver. I added a mfd driver which by
default probes atmel_serial driver and if in dt is specified to probe
the spi driver, then the spi-at91-usart driver will be probed. The
compatible for atmel_serial is now the compatible for at91-usart mfd
driver and compatilbe for atmel_serial driver was changed in order to
keep the bindings for serial as they are.
Changes in v10:
-fixed kbuild test robot warning
Changes in v9:
- minor changes
- rebased on top of broonie/for-4.19
Changes in v8:
- fixed passing an empty mfd cell if "atmel,usart-mode" value is invalid
Changes in v7:
- synced up SPDIX license with module license
- numbering of usart modes starts from 0 insteand of 1
Changes in v6:
- removed unused compatible strings from serial and spi drivers
Changes in v5:
- fixed usage of stdout-path property with atmel_serial driver
Changes in v4:
- modified the spi driver to use cs gpio support form spi subsystem
- fixed dma transfers for serial driver
- squashed binding for spi and serial and moved them to mfd/atmel-usart.txt
Changes in v3:
- fixed spi slaves probing
Changes in v2:
- added at91-usart mfd driver
- modified spi-at91-usart driver to work as mfd driver child
- modified atmel_serial driver to work as mfd driver child
Changes in v1:
- added spi-at91-usart driver
Radu Pirea (6):
MAINTAINERS: add at91 usart mfd driver
dt-bindings: add binding for atmel-usart in SPI mode
mfd: at91-usart: added mfd driver for usart
MAINTAINERS: add at91 usart spi driver
spi: at91-usart: add driver for at91-usart as spi
tty/serial: atmel: change the driver to work under at91-usart mfd
.../bindings/{serial => mfd}/atmel-usart.txt | 25 +-
MAINTAINERS | 16 +
drivers/mfd/Kconfig | 9 +
drivers/mfd/Makefile | 1 +
drivers/mfd/at91-usart.c | 71 +++
drivers/spi/Kconfig | 9 +
drivers/spi/Makefile | 1 +
drivers/spi/spi-at91-usart.c | 432 ++++++++++++++++++
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/atmel_serial.c | 42 +-
include/dt-bindings/mfd/at91-usart.h | 17 +
11 files changed, 607 insertions(+), 17 deletions(-)
rename Documentation/devicetree/bindings/{serial => mfd}/atmel-usart.txt (76%)
create mode 100644 drivers/mfd/at91-usart.c
create mode 100644 drivers/spi/spi-at91-usart.c
create mode 100644 include/dt-bindings/mfd/at91-usart.h
--
2.18.0
This patch moves the bindings for serial from serial/atmel-usart.txt to
mfd/atmel-usart.txt and adds bindings for USART in SPI mode.
Signed-off-by: Radu Pirea <[email protected]>
Reviewed-by: Rob Herring <[email protected]>
---
.../bindings/{serial => mfd}/atmel-usart.txt | 25 +++++++++++++++++--
include/dt-bindings/mfd/at91-usart.h | 17 +++++++++++++
2 files changed, 40 insertions(+), 2 deletions(-)
rename Documentation/devicetree/bindings/{serial => mfd}/atmel-usart.txt (76%)
create mode 100644 include/dt-bindings/mfd/at91-usart.h
diff --git a/Documentation/devicetree/bindings/serial/atmel-usart.txt b/Documentation/devicetree/bindings/mfd/atmel-usart.txt
similarity index 76%
rename from Documentation/devicetree/bindings/serial/atmel-usart.txt
rename to Documentation/devicetree/bindings/mfd/atmel-usart.txt
index 7c0d6b2f53e4..0348fef0f497 100644
--- a/Documentation/devicetree/bindings/serial/atmel-usart.txt
+++ b/Documentation/devicetree/bindings/mfd/atmel-usart.txt
@@ -1,6 +1,6 @@
* Atmel Universal Synchronous Asynchronous Receiver/Transmitter (USART)
-Required properties:
+Required properties for USART:
- compatible: Should be "atmel,<chip>-usart" or "atmel,<chip>-dbgu"
The compatible <chip> indicated will be the first SoC to support an
additional mode or an USART new feature.
@@ -11,7 +11,13 @@ Required properties:
Required elements: "usart"
- clocks: phandles to input clocks.
-Optional properties:
+Required properties for USART in SPI mode:
+- #size-cells : Must be <0>
+- #address-cells : Must be <1>
+- cs-gpios: chipselects (internal cs not supported)
+- atmel,usart-mode : Must be <AT91_USART_MODE_SPI> (found in dt-bindings/mfd/at91-usart.h)
+
+Optional properties in serial mode:
- atmel,use-dma-rx: use of PDC or DMA for receiving data
- atmel,use-dma-tx: use of PDC or DMA for transmitting data
- {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD line respectively.
@@ -62,3 +68,18 @@ Example:
dma-names = "tx", "rx";
atmel,fifo-size = <32>;
};
+
+- SPI mode:
+ #include <dt-bindings/mfd/at91-usart.h>
+
+ spi0: spi@f001c000 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ compatible = "atmel,at91rm9200-usart", "atmel,at91sam9260-usart";
+ atmel,usart-mode = <AT91_USART_MODE_SPI>;
+ reg = <0xf001c000 0x100>;
+ interrupts = <12 IRQ_TYPE_LEVEL_HIGH>;
+ clocks = <&usart0_clk>;
+ clock-names = "usart";
+ cs-gpios = <&pioB 3 0>;
+ };
diff --git a/include/dt-bindings/mfd/at91-usart.h b/include/dt-bindings/mfd/at91-usart.h
new file mode 100644
index 000000000000..2de5bc312e1e
--- /dev/null
+++ b/include/dt-bindings/mfd/at91-usart.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * This header provides macros for AT91 USART DT bindings.
+ *
+ * Copyright (C) 2018 Microchip Technology
+ *
+ * Author: Radu Pirea <[email protected]>
+ *
+ */
+
+#ifndef __DT_BINDINGS_AT91_USART_H__
+#define __DT_BINDINGS_AT91_USART_H__
+
+#define AT91_USART_MODE_SERIAL 0
+#define AT91_USART_MODE_SPI 1
+
+#endif /* __DT_BINDINGS_AT91_USART_H__ */
--
2.18.0
This patch modifies the place where resources and device tree properties
are searched.
Signed-off-by: Radu Pirea <[email protected]>
Acked-by: Richard Genoud <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
---
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/atmel_serial.c | 42 ++++++++++++++++++++-----------
2 files changed, 28 insertions(+), 15 deletions(-)
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index df8bd0c7b97d..32886c304641 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -118,6 +118,7 @@ config SERIAL_ATMEL
depends on ARCH_AT91 || COMPILE_TEST
select SERIAL_CORE
select SERIAL_MCTRL_GPIO if GPIOLIB
+ select MFD_AT91_USART
help
This enables the driver for the on-chip UARTs of the Atmel
AT91 processors.
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 8e4428725848..267d4d1de3f8 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -193,8 +193,7 @@ static struct console atmel_console;
#if defined(CONFIG_OF)
static const struct of_device_id atmel_serial_dt_ids[] = {
- { .compatible = "atmel,at91rm9200-usart" },
- { .compatible = "atmel,at91sam9260-usart" },
+ { .compatible = "atmel,at91rm9200-usart-serial" },
{ /* sentinel */ }
};
#endif
@@ -915,6 +914,7 @@ static void atmel_tx_dma(struct uart_port *port)
static int atmel_prepare_tx_dma(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+ struct device *mfd_dev = port->dev->parent;
dma_cap_mask_t mask;
struct dma_slave_config config;
int ret, nent;
@@ -922,7 +922,7 @@ static int atmel_prepare_tx_dma(struct uart_port *port)
dma_cap_zero(mask);
dma_cap_set(DMA_SLAVE, mask);
- atmel_port->chan_tx = dma_request_slave_channel(port->dev, "tx");
+ atmel_port->chan_tx = dma_request_slave_channel(mfd_dev, "tx");
if (atmel_port->chan_tx == NULL)
goto chan_err;
dev_info(port->dev, "using %s for tx DMA transfers\n",
@@ -1093,6 +1093,7 @@ static void atmel_rx_from_dma(struct uart_port *port)
static int atmel_prepare_rx_dma(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+ struct device *mfd_dev = port->dev->parent;
struct dma_async_tx_descriptor *desc;
dma_cap_mask_t mask;
struct dma_slave_config config;
@@ -1104,7 +1105,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
dma_cap_zero(mask);
dma_cap_set(DMA_CYCLIC, mask);
- atmel_port->chan_rx = dma_request_slave_channel(port->dev, "rx");
+ atmel_port->chan_rx = dma_request_slave_channel(mfd_dev, "rx");
if (atmel_port->chan_rx == NULL)
goto chan_err;
dev_info(port->dev, "using %s for rx DMA transfers\n",
@@ -2222,8 +2223,8 @@ static const char *atmel_type(struct uart_port *port)
*/
static void atmel_release_port(struct uart_port *port)
{
- struct platform_device *pdev = to_platform_device(port->dev);
- int size = pdev->resource[0].end - pdev->resource[0].start + 1;
+ struct platform_device *mpdev = to_platform_device(port->dev->parent);
+ int size = resource_size(mpdev->resource);
release_mem_region(port->mapbase, size);
@@ -2238,8 +2239,8 @@ static void atmel_release_port(struct uart_port *port)
*/
static int atmel_request_port(struct uart_port *port)
{
- struct platform_device *pdev = to_platform_device(port->dev);
- int size = pdev->resource[0].end - pdev->resource[0].start + 1;
+ struct platform_device *mpdev = to_platform_device(port->dev->parent);
+ int size = resource_size(mpdev->resource);
if (!request_mem_region(port->mapbase, size, "atmel_serial"))
return -EBUSY;
@@ -2341,27 +2342,28 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port,
{
int ret;
struct uart_port *port = &atmel_port->uart;
+ struct platform_device *mpdev = to_platform_device(pdev->dev.parent);
atmel_init_property(atmel_port, pdev);
atmel_set_ops(port);
- uart_get_rs485_mode(&pdev->dev, &port->rs485);
+ uart_get_rs485_mode(&mpdev->dev, &port->rs485);
port->iotype = UPIO_MEM;
port->flags = UPF_BOOT_AUTOCONF | UPF_IOREMAP;
port->ops = &atmel_pops;
port->fifosize = 1;
port->dev = &pdev->dev;
- port->mapbase = pdev->resource[0].start;
- port->irq = pdev->resource[1].start;
+ port->mapbase = mpdev->resource[0].start;
+ port->irq = mpdev->resource[1].start;
port->rs485_config = atmel_config_rs485;
- port->membase = NULL;
+ port->membase = NULL;
memset(&atmel_port->rx_ring, 0, sizeof(atmel_port->rx_ring));
/* for console, the clock could already be configured */
if (!atmel_port->clk) {
- atmel_port->clk = clk_get(&pdev->dev, "usart");
+ atmel_port->clk = clk_get(&mpdev->dev, "usart");
if (IS_ERR(atmel_port->clk)) {
ret = PTR_ERR(atmel_port->clk);
atmel_port->clk = NULL;
@@ -2694,13 +2696,22 @@ static void atmel_serial_probe_fifos(struct atmel_uart_port *atmel_port,
static int atmel_serial_probe(struct platform_device *pdev)
{
struct atmel_uart_port *atmel_port;
- struct device_node *np = pdev->dev.of_node;
+ struct device_node *np = pdev->dev.parent->of_node;
void *data;
int ret = -ENODEV;
bool rs485_enabled;
BUILD_BUG_ON(ATMEL_SERIAL_RINGSIZE & (ATMEL_SERIAL_RINGSIZE - 1));
+ /*
+ * In device tree there is no node with "atmel,at91rm9200-usart-serial"
+ * as compatible string. This driver is probed by at91-usart mfd driver
+ * which is just a wrapper over the atmel_serial driver and
+ * spi-at91-usart driver. All attributes needed by this driver are
+ * found in of_node of parent.
+ */
+ pdev->dev.of_node = np;
+
ret = of_alias_get_id(np, "serial");
if (ret < 0)
/* port id not found in platform data nor device-tree aliases:
@@ -2836,6 +2847,7 @@ static int atmel_serial_remove(struct platform_device *pdev)
clk_put(atmel_port->clk);
atmel_port->clk = NULL;
+ pdev->dev.of_node = NULL;
return ret;
}
@@ -2846,7 +2858,7 @@ static struct platform_driver atmel_serial_driver = {
.suspend = atmel_serial_suspend,
.resume = atmel_serial_resume,
.driver = {
- .name = "atmel_usart",
+ .name = "atmel_usart_serial",
.of_match_table = of_match_ptr(atmel_serial_dt_ids),
},
};
--
2.18.0
This is the driver for at91-usart in spi mode. The USART IP can be configured
to work in many modes and one of them is SPI.
The driver was tested on sama5d3-xplained and sama5d4-xplained boards with
enc28j60 ethernet controller as slave.
Signed-off-by: Radu Pirea <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
---
drivers/spi/Kconfig | 9 +
drivers/spi/Makefile | 1 +
drivers/spi/spi-at91-usart.c | 432 +++++++++++++++++++++++++++++++++++
3 files changed, 442 insertions(+)
create mode 100644 drivers/spi/spi-at91-usart.c
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index ad5d68e1dab7..02bb35057ccd 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -83,6 +83,15 @@ config SPI_ATMEL
This selects a driver for the Atmel SPI Controller, present on
many AT91 ARM chips.
+config SPI_AT91_USART
+ tristate "Atmel USART Controller SPI driver"
+ depends on HAS_DMA
+ depends on (ARCH_AT91 || COMPILE_TEST)
+ select MFD_AT91_USART
+ help
+ This selects a driver for the AT91 USART Controller as SPI Master,
+ present on AT91 and SAMA5 SoC series.
+
config SPI_AU1550
tristate "Au1550/Au1200/Au1300 SPI Controller"
depends on MIPS_ALCHEMY
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index cb1f4378b87c..901ff606e6e5 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_SPI_LOOPBACK_TEST) += spi-loopback-test.o
obj-$(CONFIG_SPI_ALTERA) += spi-altera.o
obj-$(CONFIG_SPI_ARMADA_3700) += spi-armada-3700.o
obj-$(CONFIG_SPI_ATMEL) += spi-atmel.o
+obj-$(CONFIG_SPI_AT91_USART) += spi-at91-usart.o
obj-$(CONFIG_SPI_ATH79) += spi-ath79.o
obj-$(CONFIG_SPI_AU1550) += spi-au1550.o
obj-$(CONFIG_SPI_AXI_SPI_ENGINE) += spi-axi-spi-engine.o
diff --git a/drivers/spi/spi-at91-usart.c b/drivers/spi/spi-at91-usart.c
new file mode 100644
index 000000000000..5c6dd0d2c6a7
--- /dev/null
+++ b/drivers/spi/spi-at91-usart.c
@@ -0,0 +1,432 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for AT91 USART Controllers as SPI
+ *
+ * Copyright (C) 2018 Microchip Technology Inc.
+ * Author: Radu Pirea <[email protected]>
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+
+#include <linux/spi/spi.h>
+
+#define US_CR 0x00
+#define US_MR 0x04
+#define US_IER 0x08
+#define US_IDR 0x0C
+#define US_CSR 0x14
+#define US_RHR 0x18
+#define US_THR 0x1C
+#define US_BRGR 0x20
+#define US_VERSION 0xFC
+
+#define US_CR_RSTRX BIT(2)
+#define US_CR_RSTTX BIT(3)
+#define US_CR_RXEN BIT(4)
+#define US_CR_RXDIS BIT(5)
+#define US_CR_TXEN BIT(6)
+#define US_CR_TXDIS BIT(7)
+
+#define US_MR_SPI_MASTER 0x0E
+#define US_MR_CHRL GENMASK(7, 6)
+#define US_MR_CPHA BIT(8)
+#define US_MR_CPOL BIT(16)
+#define US_MR_CLKO BIT(18)
+#define US_MR_WRDBT BIT(20)
+#define US_MR_LOOP BIT(15)
+
+#define US_IR_RXRDY BIT(0)
+#define US_IR_TXRDY BIT(1)
+#define US_IR_OVRE BIT(5)
+
+#define US_BRGR_SIZE BIT(16)
+
+#define US_MIN_CLK_DIV 0x06
+#define US_MAX_CLK_DIV BIT(16)
+
+#define US_RESET (US_CR_RSTRX | US_CR_RSTTX)
+#define US_DISABLE (US_CR_RXDIS | US_CR_TXDIS)
+#define US_ENABLE (US_CR_RXEN | US_CR_TXEN)
+#define US_OVRE_RXRDY_IRQS (US_IR_OVRE | US_IR_RXRDY)
+
+#define US_INIT \
+ (US_MR_SPI_MASTER | US_MR_CHRL | US_MR_CLKO | US_MR_WRDBT)
+
+/* Register access macros */
+#define at91_usart_spi_readl(port, reg) \
+ readl_relaxed((port)->regs + US_##reg)
+#define at91_usart_spi_writel(port, reg, value) \
+ writel_relaxed((value), (port)->regs + US_##reg)
+
+#define at91_usart_spi_readb(port, reg) \
+ readb_relaxed((port)->regs + US_##reg)
+#define at91_usart_spi_writeb(port, reg, value) \
+ writeb_relaxed((value), (port)->regs + US_##reg)
+
+struct at91_usart_spi {
+ struct spi_transfer *current_transfer;
+ void __iomem *regs;
+ struct device *dev;
+ struct clk *clk;
+
+ /*used in interrupt to protect data reading*/
+ spinlock_t lock;
+
+ int irq;
+ unsigned int current_tx_remaining_bytes;
+ unsigned int current_rx_remaining_bytes;
+
+ u32 spi_clk;
+ u32 status;
+
+ bool xfer_failed;
+};
+
+static inline u32 at91_usart_spi_tx_ready(struct at91_usart_spi *aus)
+{
+ return aus->status & US_IR_TXRDY;
+}
+
+static inline u32 at91_usart_spi_rx_ready(struct at91_usart_spi *aus)
+{
+ return aus->status & US_IR_RXRDY;
+}
+
+static inline u32 at91_usart_spi_check_overrun(struct at91_usart_spi *aus)
+{
+ return aus->status & US_IR_OVRE;
+}
+
+static inline u32 at91_usart_spi_read_status(struct at91_usart_spi *aus)
+{
+ aus->status = at91_usart_spi_readl(aus, CSR);
+ return aus->status;
+}
+
+static inline void at91_usart_spi_tx(struct at91_usart_spi *aus)
+{
+ unsigned int len = aus->current_transfer->len;
+ unsigned int remaining = aus->current_tx_remaining_bytes;
+ const u8 *tx_buf = aus->current_transfer->tx_buf;
+
+ if (!remaining)
+ return;
+
+ if (at91_usart_spi_tx_ready(aus)) {
+ at91_usart_spi_writeb(aus, THR, tx_buf[len - remaining]);
+ aus->current_tx_remaining_bytes--;
+ }
+}
+
+static inline void at91_usart_spi_rx(struct at91_usart_spi *aus)
+{
+ int len = aus->current_transfer->len;
+ int remaining = aus->current_rx_remaining_bytes;
+ u8 *rx_buf = aus->current_transfer->rx_buf;
+
+ if (!remaining)
+ return;
+
+ rx_buf[len - remaining] = at91_usart_spi_readb(aus, RHR);
+ aus->current_rx_remaining_bytes--;
+}
+
+static inline void
+at91_usart_spi_set_xfer_speed(struct at91_usart_spi *aus,
+ struct spi_transfer *xfer)
+{
+ at91_usart_spi_writel(aus, BRGR,
+ DIV_ROUND_UP(aus->spi_clk, xfer->speed_hz));
+}
+
+static irqreturn_t at91_usart_spi_interrupt(int irq, void *dev_id)
+{
+ struct spi_controller *controller = dev_id;
+ struct at91_usart_spi *aus = spi_master_get_devdata(controller);
+
+ spin_lock(&aus->lock);
+ at91_usart_spi_read_status(aus);
+
+ if (at91_usart_spi_check_overrun(aus)) {
+ aus->xfer_failed = true;
+ at91_usart_spi_writel(aus, IDR, US_IR_OVRE | US_IR_RXRDY);
+ spin_unlock(&aus->lock);
+ return IRQ_HANDLED;
+ }
+
+ if (at91_usart_spi_rx_ready(aus)) {
+ at91_usart_spi_rx(aus);
+ spin_unlock(&aus->lock);
+ return IRQ_HANDLED;
+ }
+
+ spin_unlock(&aus->lock);
+
+ return IRQ_NONE;
+}
+
+static int at91_usart_spi_setup(struct spi_device *spi)
+{
+ struct at91_usart_spi *aus = spi_master_get_devdata(spi->controller);
+ u32 *ausd = spi->controller_state;
+ unsigned int mr = at91_usart_spi_readl(aus, MR);
+ u8 bits = spi->bits_per_word;
+
+ if (bits != 8) {
+ dev_dbg(&spi->dev, "Only 8 bits per word are supported\n");
+ return -EINVAL;
+ }
+
+ if (spi->mode & SPI_CPOL)
+ mr |= US_MR_CPOL;
+ else
+ mr &= ~US_MR_CPOL;
+
+ if (spi->mode & SPI_CPHA)
+ mr |= US_MR_CPHA;
+ else
+ mr &= ~US_MR_CPHA;
+
+ if (spi->mode & SPI_LOOP)
+ mr |= US_MR_LOOP;
+ else
+ mr &= ~US_MR_LOOP;
+
+ if (!ausd) {
+ ausd = kzalloc(sizeof(*ausd), GFP_KERNEL);
+ if (!ausd)
+ return -ENOMEM;
+
+ spi->controller_state = ausd;
+ }
+
+ *ausd = mr;
+
+ dev_dbg(&spi->dev,
+ "setup: bpw %u mode 0x%x -> mr %d %08x\n",
+ bits, spi->mode, spi->chip_select, mr);
+
+ return 0;
+}
+
+int at91_usart_spi_transfer_one(struct spi_controller *ctlr,
+ struct spi_device *spi,
+ struct spi_transfer *xfer)
+{
+ struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
+
+ at91_usart_spi_set_xfer_speed(aus, xfer);
+ aus->xfer_failed = false;
+ aus->current_transfer = xfer;
+ aus->current_tx_remaining_bytes = xfer->len;
+ aus->current_rx_remaining_bytes = xfer->len;
+
+ while ((aus->current_tx_remaining_bytes ||
+ aus->current_rx_remaining_bytes) && !aus->xfer_failed) {
+ at91_usart_spi_read_status(aus);
+ at91_usart_spi_tx(aus);
+ cpu_relax();
+ }
+
+ if (aus->xfer_failed) {
+ dev_err(aus->dev, "Overrun!\n");
+ return -EIO;
+ }
+
+ return 0;
+}
+
+int at91_usart_spi_prepare_message(struct spi_controller *ctlr,
+ struct spi_message *message)
+{
+ struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
+ struct spi_device *spi = message->spi;
+ u32 *ausd = spi->controller_state;
+
+ at91_usart_spi_writel(aus, CR, US_ENABLE);
+ at91_usart_spi_writel(aus, IER, US_OVRE_RXRDY_IRQS);
+ at91_usart_spi_writel(aus, MR, *ausd);
+
+ return 0;
+}
+
+int at91_usart_spi_unprepare_message(struct spi_controller *ctlr,
+ struct spi_message *message)
+{
+ struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
+
+ at91_usart_spi_writel(aus, CR, US_RESET | US_DISABLE);
+ at91_usart_spi_writel(aus, IDR, US_OVRE_RXRDY_IRQS);
+
+ return 0;
+}
+
+static void at91_usart_spi_cleanup(struct spi_device *spi)
+{
+ struct at91_usart_spi_device *ausd = spi->controller_state;
+
+ spi->controller_state = NULL;
+ kfree(ausd);
+}
+
+static void at91_usart_spi_init(struct at91_usart_spi *aus)
+{
+ at91_usart_spi_writel(aus, MR, US_INIT);
+ at91_usart_spi_writel(aus, CR, US_RESET | US_DISABLE);
+}
+
+static int at91_usart_gpio_setup(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.parent->of_node;
+ int i;
+ int ret;
+ int nb;
+
+ if (!np)
+ return -EINVAL;
+
+ nb = of_gpio_named_count(np, "cs-gpios");
+ for (i = 0; i < nb; i++) {
+ int cs_gpio = of_get_named_gpio(np, "cs-gpios", i);
+
+ if (cs_gpio < 0)
+ return cs_gpio;
+
+ if (gpio_is_valid(cs_gpio)) {
+ ret = devm_gpio_request_one(&pdev->dev, cs_gpio,
+ GPIOF_DIR_OUT,
+ dev_name(&pdev->dev));
+ if (ret)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static int at91_usart_spi_probe(struct platform_device *pdev)
+{
+ struct resource *regs;
+ struct spi_controller *controller;
+ struct at91_usart_spi *aus;
+ struct clk *clk;
+ int irq;
+ int ret;
+
+ regs = platform_get_resource(to_platform_device(pdev->dev.parent),
+ IORESOURCE_MEM, 0);
+ if (!regs)
+ return -EINVAL;
+
+ irq = platform_get_irq(to_platform_device(pdev->dev.parent), 0);
+ if (irq < 0)
+ return irq;
+
+ clk = devm_clk_get(pdev->dev.parent, "usart");
+ if (IS_ERR(clk))
+ return PTR_ERR(clk);
+
+ ret = -ENOMEM;
+ controller = spi_alloc_master(&pdev->dev, sizeof(*aus));
+ if (!controller)
+ goto at91_usart_spi_probe_fail;
+
+ ret = at91_usart_gpio_setup(pdev);
+ if (ret)
+ goto at91_usart_spi_probe_fail;
+
+ controller->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP | SPI_CS_HIGH;
+ controller->dev.of_node = pdev->dev.parent->of_node;
+ controller->bits_per_word_mask = SPI_BPW_MASK(8);
+ controller->setup = at91_usart_spi_setup;
+ controller->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
+ controller->transfer_one = at91_usart_spi_transfer_one;
+ controller->prepare_message = at91_usart_spi_prepare_message;
+ controller->unprepare_message = at91_usart_spi_unprepare_message;
+ controller->cleanup = at91_usart_spi_cleanup;
+ controller->max_speed_hz = DIV_ROUND_UP(clk_get_rate(clk),
+ US_MIN_CLK_DIV);
+ controller->min_speed_hz = DIV_ROUND_UP(clk_get_rate(clk),
+ US_MAX_CLK_DIV);
+ platform_set_drvdata(pdev, controller);
+
+ aus = spi_master_get_devdata(controller);
+
+ aus->dev = &pdev->dev;
+ aus->regs = devm_ioremap_resource(&pdev->dev, regs);
+ if (IS_ERR(aus->regs)) {
+ ret = PTR_ERR(aus->regs);
+ goto at91_usart_spi_probe_fail;
+ }
+
+ aus->irq = irq;
+ aus->clk = clk;
+
+ ret = devm_request_irq(&pdev->dev, irq, at91_usart_spi_interrupt, 0,
+ dev_name(&pdev->dev), controller);
+ if (ret)
+ goto at91_usart_spi_probe_fail;
+
+ ret = clk_prepare_enable(clk);
+ if (ret)
+ goto at91_usart_spi_probe_fail;
+
+ aus->spi_clk = clk_get_rate(clk);
+ at91_usart_spi_init(aus);
+
+ spin_lock_init(&aus->lock);
+ ret = devm_spi_register_master(&pdev->dev, controller);
+ if (ret)
+ goto at91_usart_fail_register_master;
+
+ dev_info(&pdev->dev,
+ "AT91 USART SPI Controller version 0x%x at %pa (irq %d)\n",
+ at91_usart_spi_readl(aus, VERSION),
+ ®s->start, irq);
+
+ return 0;
+
+at91_usart_fail_register_master:
+ clk_disable_unprepare(clk);
+at91_usart_spi_probe_fail:
+ spi_master_put(controller);
+ return ret;
+}
+
+static int at91_usart_spi_remove(struct platform_device *pdev)
+{
+ struct spi_controller *ctlr = platform_get_drvdata(pdev);
+ struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
+
+ clk_disable_unprepare(aus->clk);
+
+ return 0;
+}
+
+static const struct of_device_id at91_usart_spi_dt_ids[] = {
+ { .compatible = "microchip,at91sam9g45-usart-spi"},
+ { /* sentinel */}
+};
+
+MODULE_DEVICE_TABLE(of, at91_usart_spi_dt_ids);
+
+static struct platform_driver at91_usart_spi_driver = {
+ .driver = {
+ .name = "at91_usart_spi",
+ },
+ .probe = at91_usart_spi_probe,
+ .remove = at91_usart_spi_remove,
+};
+
+module_platform_driver(at91_usart_spi_driver);
+
+MODULE_DESCRIPTION("Microchip AT91 USART SPI Controller driver");
+MODULE_AUTHOR("Radu Pirea <[email protected]>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:at91_usart_spi");
--
2.18.0
Added entry for at91 usart mfd driver.
Signed-off-by: Radu Pirea <[email protected]>
---
MAINTAINERS | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 7ac6e6af5292..f849cc4acbf6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9362,6 +9362,13 @@ F: drivers/mfd/at91-usart.c
F: include/dt-bindings/mfd/at91-usart.h
F: Documentation/devicetree/bindings/mfd/atmel-usart.txt
+MICROCHIP AT91 USART SPI DRIVER
+M: Radu Pirea <[email protected]>
+L: [email protected]
+S: Supported
+F: drivers/spi/spi-at91-usart.c
+F: Documentation/devicetree/bindings/mfd/atmel-usart.txt
+
MICROCHIP KSZ SERIES ETHERNET SWITCH DRIVER
M: Woojung Huh <[email protected]>
M: Microchip Linux Driver Support <[email protected]>
--
2.18.0
This mfd driver is just a wrapper over atmel_serial driver and
spi-at91-usart driver. Selection of one of the drivers is based on a
property from device tree. If the property is not specified, the default
driver is atmel_serial.
Signed-off-by: Radu Pirea <[email protected]>
Acked-by: Rob Herring <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Acked-for-MFD-by: Lee Jones <[email protected]>
---
drivers/mfd/Kconfig | 9 +++++
drivers/mfd/Makefile | 1 +
drivers/mfd/at91-usart.c | 71 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 81 insertions(+)
create mode 100644 drivers/mfd/at91-usart.c
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index b860eb5aa194..a886672b960d 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -99,6 +99,15 @@ config MFD_AAT2870_CORE
additional drivers must be enabled in order to use the
functionality of the device.
+config MFD_AT91_USART
+ tristate "AT91 USART Driver"
+ select MFD_CORE
+ help
+ Select this to get support for AT91 USART IP. This is a wrapper
+ over at91-usart-serial driver and usart-spi-driver. Only one function
+ can be used at a time. The choice is done at boot time by the probe
+ function of this MFD driver according to a device tree property.
+
config MFD_ATMEL_FLEXCOM
tristate "Atmel Flexcom (Flexible Serial Communication Unit)"
select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index e9fd20dba18d..c7e66928abb9 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -184,6 +184,7 @@ obj-$(CONFIG_MFD_SPMI_PMIC) += qcom-spmi-pmic.o
obj-$(CONFIG_TPS65911_COMPARATOR) += tps65911-comparator.o
obj-$(CONFIG_MFD_TPS65090) += tps65090.o
obj-$(CONFIG_MFD_AAT2870_CORE) += aat2870-core.o
+obj-$(CONFIG_MFD_AT91_USART) += at91-usart.o
obj-$(CONFIG_MFD_ATMEL_FLEXCOM) += atmel-flexcom.o
obj-$(CONFIG_MFD_ATMEL_HLCDC) += atmel-hlcdc.o
obj-$(CONFIG_MFD_ATMEL_SMC) += atmel-smc.o
diff --git a/drivers/mfd/at91-usart.c b/drivers/mfd/at91-usart.c
new file mode 100644
index 000000000000..a4b9929c156f
--- /dev/null
+++ b/drivers/mfd/at91-usart.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for AT91 USART
+ *
+ * Copyright (C) 2018 Microchip Technology
+ *
+ * Author: Radu Pirea <[email protected]>
+ *
+ */
+
+#include <dt-bindings/mfd/at91-usart.h>
+
+#include <linux/module.h>
+#include <linux/mfd/core.h>
+#include <linux/property.h>
+
+static struct mfd_cell at91_usart_spi_subdev = {
+ .name = "at91_usart_spi",
+ .of_compatible = "microchip,at91sam9g45-usart-spi",
+ };
+
+static struct mfd_cell at91_usart_serial_subdev = {
+ .name = "atmel_usart_serial",
+ .of_compatible = "atmel,at91rm9200-usart-serial",
+ };
+
+static int at91_usart_mode_probe(struct platform_device *pdev)
+{
+ struct mfd_cell cell;
+ u32 opmode = AT91_USART_MODE_SERIAL;
+
+ device_property_read_u32(&pdev->dev, "atmel,usart-mode", &opmode);
+
+ switch (opmode) {
+ case AT91_USART_MODE_SPI:
+ cell = at91_usart_spi_subdev;
+ break;
+ case AT91_USART_MODE_SERIAL:
+ cell = at91_usart_serial_subdev;
+ break;
+ default:
+ dev_err(&pdev->dev, "atmel,usart-mode has an invalid value %u\n",
+ opmode);
+ return -EINVAL;
+ }
+
+ return devm_mfd_add_devices(&pdev->dev, PLATFORM_DEVID_AUTO, &cell, 1,
+ NULL, 0, NULL);
+}
+
+static const struct of_device_id at91_usart_mode_of_match[] = {
+ { .compatible = "atmel,at91rm9200-usart" },
+ { .compatible = "atmel,at91sam9260-usart" },
+ { /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(of, at91_usart_mode_of_match);
+
+static struct platform_driver at91_usart_mfd = {
+ .probe = at91_usart_mode_probe,
+ .driver = {
+ .name = "at91_usart_mode",
+ .of_match_table = at91_usart_mode_of_match,
+ },
+};
+
+module_platform_driver(at91_usart_mfd);
+
+MODULE_AUTHOR("Radu Pirea <[email protected]>");
+MODULE_DESCRIPTION("AT91 USART MFD driver");
+MODULE_LICENSE("GPL v2");
--
2.18.0
Added entry for at91 usart mfd driver.
Signed-off-by: Radu Pirea <[email protected]>
---
MAINTAINERS | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 9d5eeff51b5f..7ac6e6af5292 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9321,6 +9321,7 @@ M: Richard Genoud <[email protected]>
S: Maintained
F: drivers/tty/serial/atmel_serial.c
F: drivers/tty/serial/atmel_serial.h
+F: Documentation/devicetree/bindings/mfd/atmel-usart.txt
MICROCHIP / ATMEL DMA DRIVER
M: Ludovic Desroches <[email protected]>
@@ -9353,6 +9354,14 @@ S: Supported
F: drivers/mtd/nand/raw/atmel/*
F: Documentation/devicetree/bindings/mtd/atmel-nand.txt
+MICROCHIP AT91 USART MFD DRIVER
+M: Radu Pirea <[email protected]>
+L: [email protected]
+S: Supported
+F: drivers/mfd/at91-usart.c
+F: include/dt-bindings/mfd/at91-usart.h
+F: Documentation/devicetree/bindings/mfd/atmel-usart.txt
+
MICROCHIP KSZ SERIES ETHERNET SWITCH DRIVER
M: Woojung Huh <[email protected]>
M: Microchip Linux Driver Support <[email protected]>
--
2.18.0
On Mon, 25 Jun 2018, Radu Pirea wrote:
> This patch moves the bindings for serial from serial/atmel-usart.txt to
> mfd/atmel-usart.txt and adds bindings for USART in SPI mode.
>
> Signed-off-by: Radu Pirea <[email protected]>
> Reviewed-by: Rob Herring <[email protected]>
I already Acked this in V4.
> ---
> .../bindings/{serial => mfd}/atmel-usart.txt | 25 +++++++++++++++++--
> include/dt-bindings/mfd/at91-usart.h | 17 +++++++++++++
> 2 files changed, 40 insertions(+), 2 deletions(-)
> rename Documentation/devicetree/bindings/{serial => mfd}/atmel-usart.txt (76%)
> create mode 100644 include/dt-bindings/mfd/at91-usart.h
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
On Mon, 25 Jun 2018, Radu Pirea wrote:
> Added entry for at91 usart mfd driver.
>
> Signed-off-by: Radu Pirea <[email protected]>
> ---
> MAINTAINERS | 9 +++++++++
> 1 file changed, 9 insertions(+)
For my own reference:
Acked-for-MFD-by: Lee Jones <[email protected]>
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
On Mon, Jun 25, 2018 at 08:22:29PM +0300, Radu Pirea wrote:
This is mostly good, just a couple of small things:
> +config SPI_AT91_USART
> + tristate "Atmel USART Controller SPI driver"
> + depends on HAS_DMA
> + depends on (ARCH_AT91 || COMPILE_TEST)
> + select MFD_AT91_USART
Why is this selecting rather than depending on the MFD like we normally
do?
> @@ -0,0 +1,432 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for AT91 USART Controllers as SPI
> + *
> + * Copyright (C) 2018 Microchip Technology Inc.
> + * Author: Radu Pirea <[email protected]>
> + */
Please use C++ comments for the whole block so it looks a bit more
intentional.
Otherwise
Reviwed-by: Mark Brown <[email protected]>
On 25/06/2018 at 19:22, Radu Pirea wrote:
> Hello,
>
> This is the second version of driver. I added a mfd driver which by
> default probes atmel_serial driver and if in dt is specified to probe
> the spi driver, then the spi-at91-usart driver will be probed. The
> compatible for atmel_serial is now the compatible for at91-usart mfd
> driver and compatilbe for atmel_serial driver was changed in order to
> keep the bindings for serial as they are.
>
> Changes in v10:
> -fixed kbuild test robot warning
>
> Changes in v9:
> - minor changes
> - rebased on top of broonie/for-4.19
>
> Changes in v8:
> - fixed passing an empty mfd cell if "atmel,usart-mode" value is invalid
>
> Changes in v7:
> - synced up SPDIX license with module license
> - numbering of usart modes starts from 0 insteand of 1
>
> Changes in v6:
> - removed unused compatible strings from serial and spi drivers
>
> Changes in v5:
> - fixed usage of stdout-path property with atmel_serial driver
>
> Changes in v4:
> - modified the spi driver to use cs gpio support form spi subsystem
> - fixed dma transfers for serial driver
> - squashed binding for spi and serial and moved them to mfd/atmel-usart.txt
>
> Changes in v3:
> - fixed spi slaves probing
>
> Changes in v2:
> - added at91-usart mfd driver
> - modified spi-at91-usart driver to work as mfd driver child
> - modified atmel_serial driver to work as mfd driver child
>
> Changes in v1:
> - added spi-at91-usart driver
>
>
> Radu Pirea (6):
> MAINTAINERS: add at91 usart mfd driver
> dt-bindings: add binding for atmel-usart in SPI mode
> mfd: at91-usart: added mfd driver for usart
> MAINTAINERS: add at91 usart spi driver
> spi: at91-usart: add driver for at91-usart as spi
> tty/serial: atmel: change the driver to work under at91-usart mfd
For the record or if needed by the MAINTAINERS changes, you can add my:
Acked-by: Nicolas Ferre <[email protected]>
for the whole series.
Once the remarks by Mark are addressed, you can certainly re-send the
series with all tags collected for Lee to take it, if he is okay with
this process, of course...
Thanks, best regards,
Nicolas
> .../bindings/{serial => mfd}/atmel-usart.txt | 25 +-
> MAINTAINERS | 16 +
> drivers/mfd/Kconfig | 9 +
> drivers/mfd/Makefile | 1 +
> drivers/mfd/at91-usart.c | 71 +++
> drivers/spi/Kconfig | 9 +
> drivers/spi/Makefile | 1 +
> drivers/spi/spi-at91-usart.c | 432 ++++++++++++++++++
> drivers/tty/serial/Kconfig | 1 +
> drivers/tty/serial/atmel_serial.c | 42 +-
> include/dt-bindings/mfd/at91-usart.h | 17 +
> 11 files changed, 607 insertions(+), 17 deletions(-)
> rename Documentation/devicetree/bindings/{serial => mfd}/atmel-usart.txt (76%)
> create mode 100644 drivers/mfd/at91-usart.c
> create mode 100644 drivers/spi/spi-at91-usart.c
> create mode 100644 include/dt-bindings/mfd/at91-usart.h
>
--
Nicolas Ferre
On Wed, 11 Jul 2018, Nicolas Ferre wrote:
> On 25/06/2018 at 19:22, Radu Pirea wrote:
> > Hello,
> >
> > This is the second version of driver. I added a mfd driver which by
> > default probes atmel_serial driver and if in dt is specified to probe
> > the spi driver, then the spi-at91-usart driver will be probed. The
> > compatible for atmel_serial is now the compatible for at91-usart mfd
> > driver and compatilbe for atmel_serial driver was changed in order to
> > keep the bindings for serial as they are.
> >
> > Changes in v10:
> > -fixed kbuild test robot warning
> >
> > Changes in v9:
> > - minor changes
> > - rebased on top of broonie/for-4.19
> >
> > Changes in v8:
> > - fixed passing an empty mfd cell if "atmel,usart-mode" value is invalid
> >
> > Changes in v7:
> > - synced up SPDIX license with module license
> > - numbering of usart modes starts from 0 insteand of 1
> >
> > Changes in v6:
> > - removed unused compatible strings from serial and spi drivers
> >
> > Changes in v5:
> > - fixed usage of stdout-path property with atmel_serial driver
> >
> > Changes in v4:
> > - modified the spi driver to use cs gpio support form spi subsystem
> > - fixed dma transfers for serial driver
> > - squashed binding for spi and serial and moved them to mfd/atmel-usart.txt
> >
> > Changes in v3:
> > - fixed spi slaves probing
> >
> > Changes in v2:
> > - added at91-usart mfd driver
> > - modified spi-at91-usart driver to work as mfd driver child
> > - modified atmel_serial driver to work as mfd driver child
> >
> > Changes in v1:
> > - added spi-at91-usart driver
> >
> >
> > Radu Pirea (6):
> > MAINTAINERS: add at91 usart mfd driver
> > dt-bindings: add binding for atmel-usart in SPI mode
> > mfd: at91-usart: added mfd driver for usart
> > MAINTAINERS: add at91 usart spi driver
> > spi: at91-usart: add driver for at91-usart as spi
> > tty/serial: atmel: change the driver to work under at91-usart mfd
>
> For the record or if needed by the MAINTAINERS changes, you can add my:
> Acked-by: Nicolas Ferre <[email protected]>
> for the whole series.
>
> Once the remarks by Mark are addressed, you can certainly re-send the series
> with all tags collected for Lee to take it, if he is okay with this process,
> of course...
That's fine. No problem.
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
On 07/10/2018 09:15 PM, Mark Brown wrote:
> On Mon, Jun 25, 2018 at 08:22:29PM +0300, Radu Pirea wrote:
>
> This is mostly good, just a couple of small things:
>
>> +config SPI_AT91_USART
>> + tristate "Atmel USART Controller SPI driver"
>> + depends on HAS_DMA
>> + depends on (ARCH_AT91 || COMPILE_TEST)
>> + select MFD_AT91_USART
>
> Why is this selecting rather than depending on the MFD like we normally
> do?
>
Hi Mark,
If I add depends instead of select, current defconfigs will be broken
and the proper driver will not be selected. Like this, there is no
required change in any defconfig. Selecting the serial or spi driver
from menuconfig makes the MFD completely transparent.
>> @@ -0,0 +1,432 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Driver for AT91 USART Controllers as SPI
>> + *
>> + * Copyright (C) 2018 Microchip Technology Inc.
>> + * Author: Radu Pirea <[email protected]>
>> + */
>
> Please use C++ comments for the whole block so it looks a bit more
> intentional.
Ok. I will change it.
>
> Otherwise
>
> Reviwed-by: Mark Brown <[email protected]>
>
On 13/07/2018 12:56:22+0300, Radu Pirea wrote:
>
>
> On 07/10/2018 09:15 PM, Mark Brown wrote:
> > On Mon, Jun 25, 2018 at 08:22:29PM +0300, Radu Pirea wrote:
> >
> > This is mostly good, just a couple of small things:
> >
> > > +config SPI_AT91_USART
> > > + tristate "Atmel USART Controller SPI driver"
> > > + depends on HAS_DMA
> > > + depends on (ARCH_AT91 || COMPILE_TEST)
> > > + select MFD_AT91_USART
> >
> > Why is this selecting rather than depending on the MFD like we normally
> > do?
> >
>
> Hi Mark,
>
> If I add depends instead of select, current defconfigs will be broken and
> the proper driver will not be selected. Like this, there is no required
> change in any defconfig. Selecting the serial or spi driver from menuconfig
> makes the MFD completely transparent.
I would say that this is true for the USART part but the SPI part can
use a depends on as it didn't exist before.
--
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com