Date:   Mon, 4 Mar 2019 20:33:05 +0100
From:   Wolfgang Grandegger <wg@...ndegger.com>
To:     Dan Murphy <dmurphy@...com>, mkl@...gutronix.de,
        davem@...emloft.net
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 4/4] can: tcan4x5x: Add tcan4x5x driver to the kernel

Hello Dan,

Am 04.03.19 um 20:07 schrieb Dan Murphy:
> Wolfgang
> 
> On 3/4/19 12:29 PM, Wolfgang Grandegger wrote:
>> Hello Dan,
>>
>> Am 01.03.19 um 19:50 schrieb Dan Murphy:
>>> Add the TCAN4x5x SPI CAN driver.  This device uses the
>>> Bosch MCAN IP core along with a SPI interface map.
>>> Register to the MCAN common core code to manage the MCAN IP.
>>>
>>> This device has a special method to indicate a write/read
>>> operation on the data payload.
>>>
>>> Signed-off-by: Dan Murphy <dmurphy@...com>
>>> ---
>>>
>>> v6 - Updated Kconfig help and added REGMAP_SPI dependency, fixed coding style issues,
>>> removed setting GPIO high in wake routine, change -EIO to return ret in init and
>>> setup functions - https://lore.kernel.org/patchwork/patch/1042443/
>>>
>>>  drivers/net/can/m_can/Kconfig    |   9 +
>>>  drivers/net/can/m_can/Makefile   |   1 +
>>>  drivers/net/can/m_can/tcan4x5x.c | 529 +++++++++++++++++++++++++++++++
>>>  3 files changed, 539 insertions(+)
>>>  create mode 100644 drivers/net/can/m_can/tcan4x5x.c
>>>
>>> diff --git a/drivers/net/can/m_can/Kconfig b/drivers/net/can/m_can/Kconfig
>>> index f7119fd72df4..cf4f32765efa 100644
>>> --- a/drivers/net/can/m_can/Kconfig
>>> +++ b/drivers/net/can/m_can/Kconfig
>>> @@ -12,3 +12,12 @@ config CAN_M_CAN_PLATFORM
>>>  	  Say Y here if you want support for IO Mapped Bosch M_CAN controller.
>>>  	  This support is for devices that have the Bosch M_CAN controller
>>>  	  IP embedded into the device and the IP is IO Mapped to the processor.
>>> +
>>> +config CAN_M_CAN_TCAN4X5X
>>> +	depends on CAN_M_CAN
>>> +	depends on REGMAP_SPI
>>> +	tristate "TCAN4X5X M_CAN device"
>>> +	---help---
>>> +	  Say Y here if you want support for Texas Instruments TCAN4x5x
>>> +	  M_CAN controller.  This device is a peripherial device that uses the
>>> +	  SPI bus for communication.
>>> diff --git a/drivers/net/can/m_can/Makefile b/drivers/net/can/m_can/Makefile
>>> index 057bbcdb3c74..e77f0eccff97 100644
>>> --- a/drivers/net/can/m_can/Makefile
>>> +++ b/drivers/net/can/m_can/Makefile
>>> @@ -4,3 +4,4 @@
>>>  
>>>  obj-$(CONFIG_CAN_M_CAN) += m_can.o
>>>  obj-$(CONFIG_CAN_M_CAN_PLATFORM) += m_can_platform.o
>>> +obj-$(CONFIG_CAN_M_CAN_TCAN4X5X) += tcan4x5x.o
>>> diff --git a/drivers/net/can/m_can/tcan4x5x.c b/drivers/net/can/m_can/tcan4x5x.c
>>> new file mode 100644
>>> index 000000000000..a91b976bb522
>>> --- /dev/null
>>> +++ b/drivers/net/can/m_can/tcan4x5x.c
>>> @@ -0,0 +1,529 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +// SPI to CAN driver for the Texas Instruments TCAN4x5x
>>> +// Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
>>> +
>>> +#include <linux/regmap.h>
>>> +#include <linux/spi/spi.h>
>>> +
>>> +#include <linux/regulator/consumer.h>
>>> +#include <linux/gpio/consumer.h>
>>> +
>>> +#include "m_can.h"
>>> +
>>> +#define DEVICE_NAME "tcan4x5x"
>>> +#define TCAN4X5X_EXT_CLK_DEF	40000000
>>> +
>>> +#define TCAN4X5X_DEV_ID0	0x00
>>> +#define TCAN4X5X_DEV_ID1	0x04
>>> +#define TCAN4X5X_REV		0x08
>>> +#define TCAN4X5X_STATUS		0x0C
>>> +#define TCAN4X5X_ERROR_STATUS	0x10
>>> +#define TCAN4X5X_CONTROL	0x14
>>> +
>>> +#define TCAN4X5X_CONFIG		0x800
>>> +#define TCAN4X5X_TS_PRESCALE	0x804
>>> +#define TCAN4X5X_TEST_REG	0x808
>>> +#define TCAN4X5X_INT_FLAGS	0x820
>>> +#define TCAN4X5X_MCAN_INT_REG	0x824
>>> +#define TCAN4X5X_INT_EN		0x830
>>> +
>>> +/* Interrupt bits */
>>> +#define TCAN4X5X_CANBUSTERMOPEN_INT_EN	BIT(30)
>>> +#define TCAN4X5X_CANHCANL_INT_EN	BIT(29)
>>> +#define TCAN4X5X_CANHBAT_INT_EN		BIT(28)
>>> +#define TCAN4X5X_CANLGND_INT_EN		BIT(27)
>>> +#define TCAN4X5X_CANBUSOPEN_INT_EN	BIT(26)
>>> +#define TCAN4X5X_CANBUSGND_INT_EN	BIT(25)
>>> +#define TCAN4X5X_CANBUSBAT_INT_EN	BIT(24)
>>> +#define TCAN4X5X_UVSUP_INT_EN		BIT(22)
>>> +#define TCAN4X5X_UVIO_INT_EN		BIT(21)
>>> +#define TCAN4X5X_TSD_INT_EN		BIT(19)
>>> +#define TCAN4X5X_ECCERR_INT_EN		BIT(16)
>>> +#define TCAN4X5X_CANINT_INT_EN		BIT(15)
>>> +#define TCAN4X5X_LWU_INT_EN		BIT(14)
>>> +#define TCAN4X5X_CANSLNT_INT_EN		BIT(10)
>>> +#define TCAN4X5X_CANDOM_INT_EN		BIT(8)
>>> +#define TCAN4X5X_CANBUS_ERR_INT_EN	BIT(5)
>>> +#define TCAN4X5X_BUS_FAULT		BIT(4)
>>> +#define TCAN4X5X_MCAN_INT		BIT(1)
>>> +#define TCAN4X5X_ENABLE_TCAN_INT	(TCAN4X5X_MCAN_INT | \
>>> +					TCAN4X5X_BUS_FAULT | \
>>> +					TCAN4X5X_CANBUS_ERR_INT_EN | \
>>> +					TCAN4X5X_CANINT_INT_EN)
>>> +
>>> +/* MCAN Interrupt bits */
>>> +#define TCAN4X5X_MCAN_IR_ARA		BIT(29)
>>> +#define TCAN4X5X_MCAN_IR_PED		BIT(28)
>>> +#define TCAN4X5X_MCAN_IR_PEA		BIT(27)
>>> +#define TCAN4X5X_MCAN_IR_WD		BIT(26)
>>> +#define TCAN4X5X_MCAN_IR_BO		BIT(25)
>>> +#define TCAN4X5X_MCAN_IR_EW		BIT(24)
>>> +#define TCAN4X5X_MCAN_IR_EP		BIT(23)
>>> +#define TCAN4X5X_MCAN_IR_ELO		BIT(22)
>>> +#define TCAN4X5X_MCAN_IR_BEU		BIT(21)
>>> +#define TCAN4X5X_MCAN_IR_BEC		BIT(20)
>>> +#define TCAN4X5X_MCAN_IR_DRX		BIT(19)
>>> +#define TCAN4X5X_MCAN_IR_TOO		BIT(18)
>>> +#define TCAN4X5X_MCAN_IR_MRAF		BIT(17)
>>> +#define TCAN4X5X_MCAN_IR_TSW		BIT(16)
>>> +#define TCAN4X5X_MCAN_IR_TEFL		BIT(15)
>>> +#define TCAN4X5X_MCAN_IR_TEFF		BIT(14)
>>> +#define TCAN4X5X_MCAN_IR_TEFW		BIT(13)
>>> +#define TCAN4X5X_MCAN_IR_TEFN		BIT(12)
>>> +#define TCAN4X5X_MCAN_IR_TFE		BIT(11)
>>> +#define TCAN4X5X_MCAN_IR_TCF		BIT(10)
>>> +#define TCAN4X5X_MCAN_IR_TC		BIT(9)
>>> +#define TCAN4X5X_MCAN_IR_HPM		BIT(8)
>>> +#define TCAN4X5X_MCAN_IR_RF1L		BIT(7)
>>> +#define TCAN4X5X_MCAN_IR_RF1F		BIT(6)
>>> +#define TCAN4X5X_MCAN_IR_RF1W		BIT(5)
>>> +#define TCAN4X5X_MCAN_IR_RF1N		BIT(4)
>>> +#define TCAN4X5X_MCAN_IR_RF0L		BIT(3)
>>> +#define TCAN4X5X_MCAN_IR_RF0F		BIT(2)
>>> +#define TCAN4X5X_MCAN_IR_RF0W		BIT(1)
>>> +#define TCAN4X5X_MCAN_IR_RF0N		BIT(0)
>>> +#define TCAN4X5X_ENABLE_MCAN_INT	(TCAN4X5X_MCAN_IR_TC | \
>>> +					TCAN4X5X_MCAN_IR_RF0N | \
>>> +					TCAN4X5X_MCAN_IR_RF1N | \
>>> +					TCAN4X5X_MCAN_IR_RF0F | \
>>> +					TCAN4X5X_MCAN_IR_RF1F)
>>> +#define TCAN4X5X_MRAM_START	0x8000
>>> +#define TCAN4X5X_MCAN_OFFSET	0x1000
>>> +#define TCAN4X5X_MAX_REGISTER	0x8fff
>>> +
>>> +#define TCAN4X5X_CLEAR_ALL_INT	0xffffffff
>>> +#define TCAN4X5X_SET_ALL_INT	0xffffffff
>>> +
>>> +#define TCAN4X5X_WRITE_CMD	(0x61 << 24)
>>> +#define TCAN4X5X_READ_CMD	(0x41 << 24)
>>> +
>>> +#define TCAN4X5X_MODE_SEL_MASK		(BIT(7) | BIT(6))
>>> +#define TCAN4X5X_MODE_SLEEP		0x00
>>> +#define TCAN4X5X_MODE_STANDBY		BIT(6)
>>> +#define TCAN4X5X_MODE_NORMAL		BIT(7)
>>> +
>>> +#define TCAN4X5X_SW_RESET	BIT(2)
>>> +
>>> +#define TCAN4X5X_MCAN_CONFIGURED	BIT(5)
>>> +#define TCAN4X5X_WATCHDOG_EN		BIT(3)
>>> +#define TCAN4X5X_WD_60_MS_TIMER		0
>>> +#define TCAN4X5X_WD_600_MS_TIMER	BIT(28)
>>> +#define TCAN4X5X_WD_3_S_TIMER		BIT(29)
>>> +#define TCAN4X5X_WD_6_S_TIMER		(BIT(28) | BIT(29))
>>> +
>>> +struct tcan4x5x_priv {
>>> +	struct regmap *regmap;
>>> +	struct spi_device *spi;
>>> +	struct mutex tcan4x5x_lock; /* SPI device lock */
>>> +
>>> +	struct m_can_classdev *mcan_dev;
>>> +
>>> +	struct gpio_desc *reset_gpio;
>>> +	struct gpio_desc *interrupt_gpio;
>>> +	struct gpio_desc *device_wake_gpio;
>>> +	struct gpio_desc *device_state_gpio;
>>> +	struct regulator *power;
>>> +
>>> +	/* Register based ip */
>>> +	int mram_start;
>>> +	int reg_offset;
>>> +};
>>> +
>>> +static struct can_bittiming_const tcan4x5x_bittiming_const = {
>>> +	.name = DEVICE_NAME,
>>> +	.tseg1_min = 2,
>>> +	.tseg1_max = 31,
>>> +	.tseg2_min = 2,
>>> +	.tseg2_max = 16,
>>> +	.sjw_max = 16,
>>> +	.brp_min = 1,
>>> +	.brp_max = 32,
>>> +	.brp_inc = 1,
>>> +};
>>> +
>>> +static struct can_bittiming_const tcan4x5x_data_bittiming_const = {
>>> +	.name = DEVICE_NAME,
>>> +	.tseg1_min = 1,
>>> +	.tseg1_max = 32,
>>> +	.tseg2_min = 1,
>>> +	.tseg2_max = 16,
>>> +	.sjw_max = 16,
>>> +	.brp_min = 1,
>>> +	.brp_max = 32,
>>> +	.brp_inc = 1,
>>> +};
>>> +
>>> +static void tcan4x5x_check_wake(struct tcan4x5x_priv *priv)
>>> +{
>>> +	int wake_state = 0;
>>> +
>>> +	if (priv->device_state_gpio)
>>> +		wake_state = gpiod_get_value(priv->device_state_gpio);
>>> +
>>> +	if (priv->device_wake_gpio && wake_state) {
>>> +		gpiod_set_value(priv->device_wake_gpio, 0);
>>> +		usleep_range(5, 50);
>>> +		gpiod_set_value(priv->device_wake_gpio, 1);
>>> +	}
>>> +}
>>> +
>>> +static int regmap_spi_gather_write(void *context, const void *reg,
>>> +				   size_t reg_len, const void *val,
>>> +				   size_t val_len)
>>> +{
>>> +	struct device *dev = context;
>>> +	struct spi_device *spi = to_spi_device(dev);
>>> +	struct spi_message m;
>>> +	u32 addr;
>>> +	struct spi_transfer t[2] = {
>>> +		{ .tx_buf = &addr, .len = reg_len, .cs_change = 0,},
>>> +		{ .tx_buf = val, .len = val_len, },
>>> +	};
>>> +
>>> +	addr = TCAN4X5X_WRITE_CMD | (*((u16 *)reg) << 8) | val_len >> 3;
>>> +
>>> +	spi_message_init(&m);
>>> +	spi_message_add_tail(&t[0], &m);
>>> +	spi_message_add_tail(&t[1], &m);
>>> +
>>> +	return spi_sync(spi, &m);
>>> +}
>>> +
>>> +static int tcan4x5x_regmap_write(void *context, const void *data, size_t count)
>>> +{
>>> +	u16 *reg = (u16 *)(data);
>>> +	const u32 *val = data + 4;
>>> +
>>> +	return regmap_spi_gather_write(context, reg, 4, val, count);
>>> +}
>>> +
>>> +static int regmap_spi_async_write(void *context,
>>> +				  const void *reg, size_t reg_len,
>>> +				  const void *val, size_t val_len,
>>> +				  struct regmap_async *a)
>>> +{
>>> +	return -ENOTSUPP;
>>> +}
>>> +
>>> +static struct regmap_async *regmap_spi_async_alloc(void)
>>> +{
>>> +	return NULL;
>>> +}
>>> +
>>> +static int tcan4x5x_regmap_read(void *context,
>>> +				const void *reg, size_t reg_size,
>>> +				void *val, size_t val_size)
>>> +{
>>> +	struct device *dev = context;
>>> +	struct spi_device *spi = to_spi_device(dev);
>>> +
>>> +	u32 addr = TCAN4X5X_READ_CMD | (*((u16 *)reg) << 8) | val_size >> 2;
>>> +
>>> +	return spi_write_then_read(spi, &addr, reg_size, (u32 *)val, val_size);
>>> +}
>>> +
>>> +static struct regmap_bus tcan4x5x_bus = {
>>> +	.write = tcan4x5x_regmap_write,
>>> +	.gather_write = regmap_spi_gather_write,
>>> +	.async_write = regmap_spi_async_write,
>>> +	.async_alloc = regmap_spi_async_alloc,
>>> +	.read = tcan4x5x_regmap_read,
>>> +	.read_flag_mask = 0x00,
>>> +	.reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
>>> +	.val_format_endian_default = REGMAP_ENDIAN_NATIVE,
>>> +};
>>> +
>>> +static u32 tcan4x5x_read_reg(struct m_can_classdev *m_can_class, int reg)
>>> +{
>>> +	struct tcan4x5x_priv *priv = (struct tcan4x5x_priv *)m_can_class->device_data;
>>> +	u32 val;
>>> +
>>> +	tcan4x5x_check_wake(priv);
>>> +
>>> +	regmap_read(priv->regmap, priv->reg_offset + reg, &val);
>>> +
>>> +	return val;
>>> +}
>>> +
>>> +static u32 tcan4x5x_read_fifo(struct m_can_classdev *m_can_class,
>>> +			      int addr_offset)
>>> +{
>>> +	struct tcan4x5x_priv *priv = (struct tcan4x5x_priv *)m_can_class->device_data;
>>> +	u32 val;
>>> +
>>> +	tcan4x5x_check_wake(priv);
>>> +
>>> +	regmap_read(priv->regmap, priv->mram_start + addr_offset, &val);
>>> +
>>> +	return val;
>>> +}
>>> +
>>> +static int tcan4x5x_write_reg(struct m_can_classdev *m_can_class,
>>> +			      int reg, int val)
>>> +{
>>> +	struct tcan4x5x_priv *priv = (struct tcan4x5x_priv *)m_can_class->device_data;
>>> +
>>> +	tcan4x5x_check_wake(priv);
>>> +
>>> +	return regmap_write(priv->regmap, priv->reg_offset + reg, val);
>>> +}
>>> +
>>> +static int tcan4x5x_write_fifo(struct m_can_classdev *m_can_class,
>>> +			       int addr_offset, int val)
>>> +{
>>> +	struct tcan4x5x_priv *priv = (struct tcan4x5x_priv *)m_can_class->device_data;
>>> +
>>> +	tcan4x5x_check_wake(priv);
>>> +
>>> +	return regmap_write(priv->regmap, priv->mram_start + addr_offset, val);
>>> +}
>>> +
>>> +static int tcan4x5x_power_enable(struct regulator *reg, int enable)
>>> +{
>>> +	if (IS_ERR_OR_NULL(reg))
>>> +		return 0;
>>> +
>>> +	if (enable)
>>> +		return regulator_enable(reg);
>>> +	else
>>> +		return regulator_disable(reg);
>>> +}
>>> +
>>> +static int tcan4x5x_write_tcan_reg(struct m_can_classdev *m_can_class,
>>> +				   int reg, int val)
>>> +{
>>> +	struct tcan4x5x_priv *priv = (struct tcan4x5x_priv *)m_can_class->device_data;
>>> +
>>> +	tcan4x5x_check_wake(priv);
>>> +
>>> +	return regmap_write(priv->regmap, reg, val);
>>> +}
>>> +
>>> +static int tcan4x5x_clear_interrupts(struct m_can_classdev *class_dev)
>>> +{
>>> +	struct tcan4x5x_priv *tcan4x5x = (struct tcan4x5x_priv *)class_dev->device_data;
>>> +	int ret;
>>> +
>>> +	tcan4x5x_check_wake(tcan4x5x);
>>> +
>>> +	ret = tcan4x5x_write_tcan_reg(class_dev, TCAN4X5X_STATUS,
>>> +				      TCAN4X5X_CLEAR_ALL_INT);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ret = tcan4x5x_write_tcan_reg(class_dev, TCAN4X5X_MCAN_INT_REG,
>>> +				      TCAN4X5X_ENABLE_MCAN_INT);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ret = tcan4x5x_write_tcan_reg(class_dev, TCAN4X5X_INT_FLAGS,
>>> +				      TCAN4X5X_CLEAR_ALL_INT);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ret = tcan4x5x_write_tcan_reg(class_dev, TCAN4X5X_ERROR_STATUS,
>>> +				      TCAN4X5X_CLEAR_ALL_INT);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	return ret;
>>> +}
>>
>> Hm, handling the interrupt seems to be a quite heavy operation. How does
>> the device and system digest small messages (dlc=0) coming in at a very
>> high rate?
>>
>> Any chance to optimize accesses be reading more than on word?
>>
> 
> The device does support writing consecutive registers.  The MCAN_INT and INT_FLAGS are consecutive
> and the STATUS and ERROR_STATUS are consecutive.  So we would still need 2 writes so not sure that this will
> optimize enough for your concern.

Yes, that's what I realized as well. Two SPI transfers instead of four
is already an improvement.

> Also the m_can code is missing bulk writes which I did not want to introduce at this time.
> My concern was more functionality and maintaining current io mapped functionality.

That's fine. I'm just curious.

> Bulk writes for peripheral devices is preferred.

Of course.

Wolfgang.

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