Re: [alsa-devel] [PATCH v4 06/15] soundwire: Add IO transfer

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 12/1/17 3:56 AM, Vinod Koul wrote:
> SoundWire bus supports read or write register(s) for SoundWire Slave
> device. sdw_read() and sdw_write() APIs are provided for single
> register read/write. sdw_nread() and sdw_nwrite() for operations on
> contiguous registers.
> 
> Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
> ---
>   drivers/soundwire/bus.c       | 275 ++++++++++++++++++++++++++++++++++++++++++
>   drivers/soundwire/bus.h       |  37 ++++++
>   include/linux/soundwire/sdw.h |  57 +++++++++
>   3 files changed, 369 insertions(+)
> 
> diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
> index 507ae85ad58e..2f108f162905 100644
> --- a/drivers/soundwire/bus.c
> +++ b/drivers/soundwire/bus.c
> @@ -3,6 +3,8 @@
>   
>   #include <linux/acpi.h>
>   #include <linux/mod_devicetable.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/soundwire/sdw_registers.h>
>   #include <linux/soundwire/sdw.h>
>   #include "bus.h"
>   
> @@ -22,6 +24,12 @@ int sdw_add_bus_master(struct sdw_bus *bus)
>   		return -ENODEV;
>   	}
>   
> +	if (!bus->ops) {
> +		dev_err(bus->dev, "SoundWire Bus ops are not set");
> +		return -EINVAL;
> +	}
> +
> +	mutex_init(&bus->msg_lock);
>   	mutex_init(&bus->bus_lock);
>   	INIT_LIST_HEAD(&bus->slaves);
>   
> @@ -97,6 +105,273 @@ void sdw_delete_bus_master(struct sdw_bus *bus)
>   }
>   EXPORT_SYMBOL(sdw_delete_bus_master);
>   
> +/*
> + * SDW IO Calls
> + */
> +
> +static inline int find_response_code(enum sdw_command_response resp)
> +{
> +	switch (resp) {
> +	case SDW_CMD_OK:
> +		return 0;
> +
> +	case SDW_CMD_IGNORED:
> +		return -ENODATA;
> +
> +	case SDW_CMD_TIMEOUT:
> +		return -ETIMEDOUT;
> +
> +	default:
> +		return -EIO;

the 'default' case will handle both SDW_CMD_FAIL (which is a bus event 
usually due to bus clash or parity issues) and SDW_CMD_FAIL_OTHER (which 
is an imp-def IP event).

Do they really belong in the same basket? From a debug perspective there 
is quite a bit of information lost.

> +	}
> +}
> +
> +static inline int do_transfer(struct sdw_bus *bus, struct sdw_msg *msg)
> +{
> +	int retry = bus->prop.err_threshold;
> +	enum sdw_command_response resp;
> +	int ret = 0, i;
> +
> +	for (i = 0; i <= retry; i++) {
> +		resp = bus->ops->xfer_msg(bus, msg);
> +		ret = find_response_code(resp);
> +
> +		/* if cmd is ok or ignored return */
> +		if (ret == 0 || ret == -ENODATA)

Can you document why you don't retry on a CMD_IGNORED? I know there was 
a reason, I just can't remember it.

Now that I think of it, the retry on TIMEOUT makes no sense to me. The 
retry was intended for bus-level issues, where maybe a single bit error 
causes an issue without consequences, but the TIMEOUT is a completely 
different beast, it's the master IP that doesn't answer really, a 
completely different case.

> +			return ret;
> +	}
> +
> +	return ret;
> +}
> +
> +static inline int do_transfer_defer(struct sdw_bus *bus,
> +			struct sdw_msg *msg, struct sdw_defer *defer)
> +{
> +	int retry = bus->prop.err_threshold;
> +	enum sdw_command_response resp;
> +	int ret = 0, i;
> +
> +	defer->msg = msg;
> +	defer->length = msg->len;
> +
> +	for (i = 0; i <= retry; i++) {
> +		resp = bus->ops->xfer_msg_defer(bus, msg, defer);
> +		ret = find_response_code(resp);
> +		/* if cmd is ok or ignored return */
> +		if (ret == 0 || ret == -ENODATA)
> +			return ret;
> +	}
> +
> +	return ret;
> +}
> +
> +static int sdw_reset_page(struct sdw_bus *bus, u16 dev_num)
> +{
> +	int retry = bus->prop.err_threshold;
> +	enum sdw_command_response resp;
> +	int ret = 0, i;
> +
> +	for (i = 0; i <= retry; i++) {
> +		resp = bus->ops->reset_page_addr(bus, dev_num);
> +		ret = find_response_code(resp);
> +		/* if cmd is ok or ignored return */
> +		if (ret == 0 || ret == -ENODATA)
> +			return ret;
> +	}
> +
> +	return ret;
> +}
> +
> +/**
> + * sdw_transfer() - Synchronous transfer message to a SDW Slave device
> + * @bus: SDW bus
> + * @slave: SDW Slave

is this just me or this argument is not used?

> + * @msg: SDW message to be xfered
> + */
> +int sdw_transfer(struct sdw_bus *bus,
> +		struct sdw_slave *slave, struct sdw_msg *msg)
> +{
> +	int ret;
> +
> +	mutex_lock(&bus->msg_lock);
> +
> +	ret = do_transfer(bus, msg);
> +	if (ret != 0 && ret != -ENODATA)
> +		dev_err(bus->dev, "trf on Slave %d failed:%d\n",
> +				msg->dev_num, ret);
> +
> +	if (msg->page)
> +		sdw_reset_page(bus, msg->dev_num);
> +
> +	mutex_unlock(&bus->msg_lock);
> +
> +	return ret;
> +}
> +
> +/**
> + * sdw_transfer_defer() - Asynchronously transfer message to a SDW Slave device
> + * @bus: SDW bus
> + * @slave: SDW Slave

same, this argument is not used in the code below.

> + * @msg: SDW message to be xfered
> + * @defer: Defer block for signal completion
> + *
> + * Caller needs to hold the msg_lock lock while calling this
> + */
> +int sdw_transfer_defer(struct sdw_bus *bus, struct sdw_slave *slave,
> +			struct sdw_msg *msg, struct sdw_defer *defer)
> +{
> +	int ret;
> +
> +	if (!bus->ops->xfer_msg_defer)
> +		return -ENOTSUPP;
> +
> +	ret = do_transfer_defer(bus, msg, defer);
> +	if (ret != 0 && ret != -ENODATA)
> +		dev_err(bus->dev, "Defer trf on Slave %d failed:%d\n",
> +				msg->dev_num, ret);
> +
> +	if (msg->page)
> +		sdw_reset_page(bus, msg->dev_num);
> +
> +	return ret;
> +}
> +
> +
> +int sdw_fill_msg(struct sdw_msg *msg, struct sdw_slave *slave,
> +		u32 addr, size_t count, u16 dev_num, u8 flags, u8 *buf)
> +{
> +	memset(msg, 0, sizeof(*msg));
> +	msg->addr = addr;

add comment on implicit truncation to 16-bit address

> +	msg->len = count;
> +	msg->dev_num = dev_num;
> +	msg->flags = flags;
> +	msg->buf = buf;
> +	msg->ssp_sync = false;
> +	msg->page = false;
> +
> +	if (addr < SDW_REG_NO_PAGE) { /* no paging area */
> +		return 0;
> +	} else if (addr >= SDW_REG_MAX) { /* illegal addr */
> +		pr_err("SDW: Invalid address %x passed\n", addr);
> +		return -EINVAL;
> +	}
> +
> +	if (addr < SDW_REG_OPTIONAL_PAGE) { /* 32k but no page */
> +		if (slave && !slave->prop.paging_support)
> +			return 0;
> +		/* no need for else as that will fall thru to paging */
> +	}
> +
> +	/* paging madatory */

mandatory

> +	if (dev_num == SDW_ENUM_DEV_NUM || dev_num == SDW_BROADCAST_DEV_NUM) {
> +		pr_err("SDW: Invalid device for paging :%d\n", dev_num);
> +		return -EINVAL;
> +	}
> +
> +	if (!slave) {
> +		pr_err("SDW: No slave for paging addr\n");
> +		return -EINVAL;

I would move this test up, since if you have a NULL slave you should 
return an error in all case, otherwise there will be an oops in the code 
below ...

> +	} else if (!slave->prop.paging_support) {
> +		dev_err(&slave->dev,
> +			"address %x needs paging but no support", addr);
> +		return -EINVAL;
> +	}
> +
> +	msg->addr_page1 = (addr >> SDW_REG_SHIFT(SDW_SCP_ADDRPAGE1_MASK));
> +	msg->addr_page2 = (addr >> SDW_REG_SHIFT(SDW_SCP_ADDRPAGE2_MASK));
> +	msg->addr |= BIT(15);
> +	msg->page = true;

looks ok :-)

> +
> +	return 0;
> +}
> +
> +/**
> + * sdw_nread() - Read "n" contiguous SDW Slave registers
> + * @slave: SDW Slave
> + * @addr: Register address
> + * @count: length
> + * @val: Buffer for values to be read
> + */
> +int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
> +{
> +	struct sdw_msg msg;
> +	int ret;
> +
> +	ret = sdw_fill_msg(&msg, slave, addr, count,
> +			slave->dev_num, SDW_MSG_FLAG_READ, val);
> +	if (ret < 0)
> +		return ret;
> +

... if you don't test for the slave argument in the sdw_fill_msg but the 
address is correct then the rest of the code will bomb out.

> +	ret = pm_runtime_get_sync(slave->bus->dev);
> +	if (!ret)
> +		return ret;
> +
> +	ret = sdw_transfer(slave->bus, slave, &msg);
> +	pm_runtime_put(slave->bus->dev);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(sdw_nread);
> +
> +/**
> + * sdw_nwrite() - Write "n" contiguous SDW Slave registers
> + * @slave: SDW Slave
> + * @addr: Register address
> + * @count: length
> + * @val: Buffer for values to be read
> + */
> +int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
> +{
> +	struct sdw_msg msg;
> +	int ret;
> +
> +	ret = sdw_fill_msg(&msg, slave, addr, count,
> +			slave->dev_num, SDW_MSG_FLAG_WRITE, val);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = pm_runtime_get_sync(slave->bus->dev);
> +	if (!ret)
> +		return ret;
> +
> +	ret = sdw_transfer(slave->bus, slave, &msg);
> +	pm_runtime_put(slave->bus->dev);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(sdw_nwrite);
> +
> +/**
> + * sdw_read() - Read a SDW Slave register
> + * @slave: SDW Slave
> + * @addr: Register address
> + */
> +int sdw_read(struct sdw_slave *slave, u32 addr)
> +{
> +	u8 buf;
> +	int ret;
> +
> +	ret = sdw_nread(slave, addr, 1, &buf);
> +	if (ret < 0)
> +		return ret;
> +	else
> +		return buf;
> +}
> +EXPORT_SYMBOL(sdw_read);
> +
> +/**
> + * sdw_write() - Write a SDW Slave register
> + * @slave: SDW Slave
> + * @addr: Register address
> + * @value: Register value
> + */
> +int sdw_write(struct sdw_slave *slave, u32 addr, u8 value)
> +{
> +	return sdw_nwrite(slave, addr, 1, &value);
> +
> +}
> +EXPORT_SYMBOL(sdw_write);
> +
>   void sdw_extract_slave_id(struct sdw_bus *bus,
>   			u64 addr, struct sdw_slave_id *id)
>   {
> diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
> index a54921825ce0..bde5f840ca96 100644
> --- a/drivers/soundwire/bus.h
> +++ b/drivers/soundwire/bus.h
> @@ -16,4 +16,41 @@ static inline int sdw_acpi_find_slaves(struct sdw_bus *bus)
>   void sdw_extract_slave_id(struct sdw_bus *bus,
>   			u64 addr, struct sdw_slave_id *id);
>   
> +enum {
> +	SDW_MSG_FLAG_READ = 0,
> +	SDW_MSG_FLAG_WRITE,
> +};
> +
> +/**
> + * struct sdw_msg - Message structure
> + * @addr: Register address accessed in the Slave
> + * @len: number of messages
> + * @dev_num: Slave device number
> + * @addr_page1: SCP address page 1 Slave register
> + * @addr_page2: SCP address page 2 Slave register
> + * @flags: transfer flags, indicate if xfer is read or write
> + * @buf: message data buffer
> + * @ssp_sync: Send message at SSP (Stream Synchronization Point)
> + * @page: address requires paging
> + */
> +struct sdw_msg {
> +	u16 addr;
> +	u16 len;
> +	u16 dev_num;

was there a reason for dev_num with 16 bits - you have 16 values max...

> +	u8 addr_page1;
> +	u8 addr_page2;
> +	u8 flags;
> +	u8 *buf;
> +	bool ssp_sync;
> +	bool page;
> +};
> +
> +int sdw_transfer(struct sdw_bus *bus, struct sdw_slave *slave,
> +			struct sdw_msg *msg);
> +int sdw_transfer_defer(struct sdw_bus *bus, struct sdw_slave *slave,
> +			struct sdw_msg *msg, struct sdw_defer *defer);
> +
> +int sdw_fill_msg(struct sdw_msg *msg, struct sdw_slave *slave,
> +		u32 addr, size_t count, u16 dev_num, u8 flags, u8 *buf);
> +
>   #endif /* __SDW_BUS_H */
> diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
> index ddfae18f4306..d3337b5b882b 100644
> --- a/include/linux/soundwire/sdw.h
> +++ b/include/linux/soundwire/sdw.h
> @@ -31,6 +31,27 @@ enum sdw_slave_status {
>   	SDW_SLAVE_RESERVED = 3,
>   };
>   
> +/**
> + * enum sdw_command_response - Command response as defined by SDW spec
> + * @SDW_CMD_OK: cmd was successful
> + * @SDW_CMD_IGNORED: cmd was ignored
> + * @SDW_CMD_FAIL: cmd was NACKed
> + * @SDW_CMD_TIMEOUT: cmd timedout
> + * @SDW_CMD_FAIL_OTHER: cmd failed due to other reason than above
> + *
> + * NOTE: The enum is different than actual Spec as response in the Spec is
> + * combination of ACK/NAK bits
> + *
> + * SDW_CMD_TIMEOUT/FAIL_OTHER is defined for SW use, not in spec
> + */
> +enum sdw_command_response {
> +	SDW_CMD_OK = 0,
> +	SDW_CMD_IGNORED = 1,
> +	SDW_CMD_FAIL = 2,
> +	SDW_CMD_TIMEOUT = 4,
> +	SDW_CMD_FAIL_OTHER = 8,

Humm, I can't recall if/why this is a mask? does it need to be?

> +};
> +
>   /*
>    * SDW properties, defined in MIPI DisCo spec v1.0
>    */
> @@ -359,12 +380,37 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
>    * SDW master structures and APIs
>    */
>   
> +struct sdw_msg;
> +
> +/**
> + * struct sdw_defer - SDW deffered message
> + * @length: message length
> + * @complete: message completion
> + * @msg: SDW message
> + */
> +struct sdw_defer {
> +	int length;
> +	struct completion complete;
> +	struct sdw_msg *msg;
> +};
> +
>   /**
>    * struct sdw_master_ops - Master driver ops
>    * @read_prop: Read Master properties
> + * @xfer_msg: Transfer message callback
> + * @xfer_msg_defer: Defer version of transfer message callback
> + * @reset_page_addr: Reset the SCP page address registers
>    */
>   struct sdw_master_ops {
>   	int (*read_prop)(struct sdw_bus *bus);
> +
> +	enum sdw_command_response (*xfer_msg)
> +			(struct sdw_bus *bus, struct sdw_msg *msg);
> +	enum sdw_command_response (*xfer_msg_defer)
> +			(struct sdw_bus *bus, struct sdw_msg *msg,
> +			struct sdw_defer *defer);
> +	enum sdw_command_response (*reset_page_addr)
> +			(struct sdw_bus *bus, unsigned int dev_num);
>   };
>   
>   /**
> @@ -375,8 +421,10 @@ struct sdw_master_ops {
>    * @assigned: Bitmap for Slave device numbers.
>    * Bit set implies used number, bit clear implies unused number.
>    * @bus_lock: bus lock
> + * @msg_lock: message lock
>    * @ops: Master callback ops
>    * @prop: Master properties
> + * @defer_msg: Defer message
>    * @clk_stop_timeout: Clock stop timeout computed
>    */
>   struct sdw_bus {
> @@ -385,12 +433,21 @@ struct sdw_bus {
>   	struct list_head slaves;
>   	DECLARE_BITMAP(assigned, SDW_MAX_DEVICES);
>   	struct mutex bus_lock;
> +	struct mutex msg_lock;
>   	const struct sdw_master_ops *ops;
>   	struct sdw_master_prop prop;
> +	struct sdw_defer defer_msg;
>   	unsigned int clk_stop_timeout;
>   };
>   
>   int sdw_add_bus_master(struct sdw_bus *bus);
>   void sdw_delete_bus_master(struct sdw_bus *bus);
>   
> +/* messaging and data APIs */
> +
> +int sdw_read(struct sdw_slave *slave, u32 addr);
> +int sdw_write(struct sdw_slave *slave, u32 addr, u8 value);
> +int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val);
> +int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, u8 *val);
> +
>   #endif /* __SOUNDWIRE_H */
>