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Date: Tue, 31 Oct 2017 16:55:42 +0100
From: Ludovic Desroches <ludovic.desroches@...rochip.com>
To: Juergen Fitschen <jfi@...-embedded.de>
CC: Ludovic Desroches <ludovic.desroches@...rochip.com>,
Wolfram Sang <wsa@...-dreams.de>, <linux-i2c@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 3/4] i2c: at91: added slave mode support
On Fri, Oct 27, 2017 at 05:12:00PM +0200, Juergen Fitschen wrote:
> Slave mode driver is based on the concept of i2c-designware driver.
>
> Signed-off-by: Juergen Fitschen <me@....yt>
> ---
> drivers/i2c/busses/Makefile | 3 +
> drivers/i2c/busses/i2c-at91-core.c | 13 +++-
> drivers/i2c/busses/i2c-at91-slave.c | 147 ++++++++++++++++++++++++++++++++++++
> drivers/i2c/busses/i2c-at91.h | 30 +++++++-
> 4 files changed, 189 insertions(+), 4 deletions(-)
> create mode 100644 drivers/i2c/busses/i2c-at91-slave.c
>
Adding an example in Documentation/devicetree/bindings/i2c/i2c-at91.txt
could be useful.
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 2a79c3d..b38fb8e9 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -34,6 +34,9 @@ obj-$(CONFIG_I2C_ALTERA) += i2c-altera.o
> obj-$(CONFIG_I2C_ASPEED) += i2c-aspeed.o
> obj-$(CONFIG_I2C_AT91) += i2c-at91.o
> i2c-at91-objs := i2c-at91-core.o i2c-at91-master.o
> +ifeq ($(CONFIG_I2C_SLAVE),y)
> + i2c-at91-objs += i2c-at91-slave.o
> +endif
As Designware driver, I would add an entry in 'I2C Hardware Bus
Support'.
If a user wants to use the I2C GPIO driver as the I2C slave (once it has
the slave support), it's not useful to embed i2c-at91-slave code.
> obj-$(CONFIG_I2C_AU1550) += i2c-au1550.o
> obj-$(CONFIG_I2C_AXXIA) += i2c-axxia.o
> obj-$(CONFIG_I2C_BCM2835) += i2c-bcm2835.o
> diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
> index 4fed72d..3d7287c 100644
> --- a/drivers/i2c/busses/i2c-at91-core.c
> +++ b/drivers/i2c/busses/i2c-at91-core.c
> @@ -60,8 +60,10 @@ void at91_init_twi_bus(struct at91_twi_dev *dev)
> {
> at91_disable_twi_interrupts(dev);
> at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SWRST);
> -
> - at91_init_twi_bus_master(dev);
> + if (dev->slave_detected)
> + at91_init_twi_bus_slave(dev);
> + else
> + at91_init_twi_bus_master(dev);
> }
>
> static struct at91_twi_pdata at91rm9200_config = {
> @@ -243,7 +245,12 @@ static int at91_twi_probe(struct platform_device *pdev)
> dev->adapter.timeout = AT91_I2C_TIMEOUT;
> dev->adapter.dev.of_node = pdev->dev.of_node;
>
> - rc = at91_twi_probe_master(pdev, phy_addr, dev);
> + dev->slave_detected = i2c_detect_slave_mode(&pdev->dev);
> +
> + if (dev->slave_detected)
> + rc = at91_twi_probe_slave(pdev, phy_addr, dev);
> + else
> + rc = at91_twi_probe_master(pdev, phy_addr, dev);
> if (rc)
> return rc;
>
> diff --git a/drivers/i2c/busses/i2c-at91-slave.c b/drivers/i2c/busses/i2c-at91-slave.c
I need to have a look to the slave framework and to test this patch before
giving you more feedback.
Some minor comments below.
> new file mode 100644
> index 0000000..4b4808e
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-at91-slave.c
> @@ -0,0 +1,147 @@
> +/*
> + * i2c slave support for Atmel's AT91 Two-Wire Interface (TWI)
> + *
> + * Copyright (C) 2017 Juergen Fitschen <me@....yt>
> + *
> + * 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.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/interrupt.h>
> +#include <linux/pm_runtime.h>
> +
> +#include "i2c-at91.h"
> +
> +static irqreturn_t atmel_twi_interrupt_slave(int irq, void *dev_id)
> +{
> + struct at91_twi_dev *dev = dev_id;
> + const unsigned status = at91_twi_read(dev, AT91_TWI_SR);
> + const unsigned irqstatus = status & at91_twi_read(dev, AT91_TWI_IMR);
> + u8 value;
> +
> + if (!irqstatus)
> + return IRQ_NONE;
> +
> + /* slave address has been detected on I2C bus */
> + if (irqstatus & AT91_TWI_SVACC) {
> + if (status & AT91_TWI_SVREAD) {
> + i2c_slave_event(dev->slave,
> + I2C_SLAVE_READ_REQUESTED, &value);
> + writeb_relaxed(value, dev->base + AT91_TWI_THR);
> + at91_twi_write(dev, AT91_TWI_IER,
> + AT91_TWI_TXRDY | AT91_TWI_EOSACC);
> + } else {
> + i2c_slave_event(dev->slave,
> + I2C_SLAVE_WRITE_REQUESTED, &value);
> + at91_twi_write(dev, AT91_TWI_IER,
> + AT91_TWI_RXRDY | AT91_TWI_EOSACC);
> + }
> + at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_SVACC);
> + }
> +
> + /* byte transmitted to remote master */
> + if (irqstatus & AT91_TWI_TXRDY) {
> + i2c_slave_event(dev->slave, I2C_SLAVE_READ_PROCESSED, &value);
> + writeb_relaxed(value, dev->base + AT91_TWI_THR);
> + }
> +
> + /* byte received from remote master */
> + if (irqstatus & AT91_TWI_RXRDY) {
> + value = readb_relaxed(dev->base + AT91_TWI_RHR);
> + i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
> + }
> +
> + /* master sent stop */
> + if (irqstatus & AT91_TWI_EOSACC) {
> + at91_twi_write(dev, AT91_TWI_IDR,
> + AT91_TWI_TXRDY | AT91_TWI_RXRDY | AT91_TWI_EOSACC);
> + at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
> + i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &value);
> + }
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int at91_reg_slave(struct i2c_client *slave)
> +{
> + struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
> +
> + if (dev->slave)
> + return -EBUSY;
> +
> + if (slave->flags & I2C_CLIENT_TEN)
> + return -EAFNOSUPPORT;
> +
> + /* Make sure twi_clk doesn't get turned off! */
> + pm_runtime_get_sync(dev->dev);
> +
> + dev->slave = slave;
> + dev->smr = AT91_TWI_SMR_SADR(slave->addr);
> +
> + at91_init_twi_bus(dev);
> + at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
> +
> + dev_info(dev->dev, "entered slave mode (ADR=%d)\n", slave->addr);
> +
> + return 0;
> +}
> +
> +static int at91_unreg_slave(struct i2c_client *slave)
> +{
> + struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
> +
> + WARN_ON(!dev->slave);
> +
> + dev_info(dev->dev, "leaving slave mode\n");
> +
> + dev->slave = NULL;
> + dev->smr = 0;
> +
> + at91_init_twi_bus(dev);
> +
> + pm_runtime_put(dev->dev);
> +
> + return 0;
> +}
> +
> +static u32 at91_twi_func(struct i2c_adapter *adapter)
> +{
> + return I2C_FUNC_SLAVE | I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
> + | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
> +}
> +
> +static const struct i2c_algorithm at91_twi_algorithm_slave = {
> + .reg_slave = at91_reg_slave,
> + .unreg_slave = at91_unreg_slave,
> + .functionality = at91_twi_func,
> +};
> +
> +int at91_twi_probe_slave(struct platform_device *pdev,
> + u32 phy_addr, struct at91_twi_dev *dev)
> +{
> + int rc;
> +
> + rc = devm_request_irq(&pdev->dev, dev->irq, atmel_twi_interrupt_slave,
> + 0, dev_name(dev->dev), dev);
> + if (rc) {
> + dev_err(dev->dev, "Cannot get irq %d: %d\n", dev->irq, rc);
> + return rc;
> + }
> +
> + dev->adapter.algo = &at91_twi_algorithm_slave;
> +
> + return 0;
> +}
> +
> +void at91_init_twi_bus_slave(struct at91_twi_dev *dev)
> +{
> + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSDIS);
> + if (dev->slave_detected && dev->smr) {
slave_detected has been checked in the caller. smr has been set just
before calling at91_init_twi_bus().
Regards
Ludovic
> + at91_twi_write(dev, AT91_TWI_SMR, dev->smr);
> + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVEN);
> + }
> +}
> diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
> index 555b167..bb502c1 100644
> --- a/drivers/i2c/busses/i2c-at91.h
> +++ b/drivers/i2c/busses/i2c-at91.h
> @@ -53,6 +53,10 @@
> #define AT91_TWI_IADRSZ_1 0x0100 /* Internal Device Address Size */
> #define AT91_TWI_MREAD BIT(12) /* Master Read Direction */
>
> +#define AT91_TWI_SMR 0x0008 /* Slave Mode Register */
> +#define AT91_TWI_SMR_SADR_MAX 0x007f
> +#define AT91_TWI_SMR_SADR(x) (((x) & AT91_TWI_SMR_SADR_MAX) << 16)
> +
> #define AT91_TWI_IADR 0x000c /* Internal Address Register */
>
> #define AT91_TWI_CWGR 0x0010 /* Clock Waveform Generator Reg */
> @@ -63,13 +67,17 @@
> #define AT91_TWI_TXCOMP BIT(0) /* Transmission Complete */
> #define AT91_TWI_RXRDY BIT(1) /* Receive Holding Register Ready */
> #define AT91_TWI_TXRDY BIT(2) /* Transmit Holding Register Ready */
> +#define AT91_TWI_SVREAD BIT(3) /* Slave Read */
> +#define AT91_TWI_SVACC BIT(4) /* Slave Access */
> #define AT91_TWI_OVRE BIT(6) /* Overrun Error */
> #define AT91_TWI_UNRE BIT(7) /* Underrun Error */
> #define AT91_TWI_NACK BIT(8) /* Not Acknowledged */
> +#define AT91_TWI_EOSACC BIT(11) /* End Of Slave Access */
> #define AT91_TWI_LOCK BIT(23) /* TWI Lock due to Frame Errors */
>
> #define AT91_TWI_INT_MASK \
> - (AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK)
> + (AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK \
> + | AT91_TWI_SVACC | AT91_TWI_EOSACC)
>
> #define AT91_TWI_IER 0x0024 /* Interrupt Enable Register */
> #define AT91_TWI_IDR 0x0028 /* Interrupt Disable Register */
> @@ -137,6 +145,11 @@ struct at91_twi_dev {
> bool recv_len_abort;
> u32 fifo_size;
> struct at91_twi_dma dma;
> + bool slave_detected;
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> + unsigned smr;
> + struct i2c_client *slave;
> +#endif
> };
>
> unsigned at91_twi_read(struct at91_twi_dev *dev, unsigned reg);
> @@ -149,3 +162,18 @@ void at91_init_twi_bus(struct at91_twi_dev *dev);
> void at91_init_twi_bus_master(struct at91_twi_dev *dev);
> int at91_twi_probe_master(struct platform_device *pdev, u32 phy_addr,
> struct at91_twi_dev *dev);
> +
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +void at91_init_twi_bus_slave(struct at91_twi_dev *dev);
> +int at91_twi_probe_slave(struct platform_device *pdev, u32 phy_addr,
> + struct at91_twi_dev *dev);
> +
> +#else
> +static inline void at91_init_twi_bus_slave(struct at91_twi_dev *dev) {}
> +static inline int at91_twi_probe_slave(struct platform_device *pdev,
> + u32 phy_addr, struct at91_twi_dev *dev)
> +{
> + return -EINVAL;
> +}
> +
> +#endif
> --
> 2.7.4
>
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