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Commit 4e56828a authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
Browse files

fsi/fsi-master-gpio: Implement CRC error recovery 



The FSI protocol defines two modes of recovery from CRC errors,
this implements both:

 - If the device returns an ECRC (it detected a CRC error in the
   command), then we simply issue the command again.

 - If the master detects a CRC error in the response, we send
   an E_POLL command which requests a resend of the response
   without actually re-executing the command (which could otherwise
   have unwanted side effects such as dequeuing a FIFO twice).

Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: default avatarChristopher Bostic <cbostic@linux.vnet.ibm.com>
Tested-by: default avatarJoel Stanley <joel@jms.id.au>
---

Note: This was actually tested by removing some of my fixes, thus
causing us to hit occasional CRC errors during high LPC activity.
parent 0e82e5c1

drivers/fsi/fsi-master-gpio.c

+72 −18
Original line number Original line Diff line number Diff line
@@ -22,20 +22,23 @@ 
#define	FSI_BREAK_CLOCKS	256	/* Number of clocks to issue break */

#define	FSI_BREAK_CLOCKS	256	/* Number of clocks to issue break */

#define	FSI_POST_BREAK_CLOCKS	16000	/* Number clocks to set up cfam */

#define	FSI_POST_BREAK_CLOCKS	16000	/* Number clocks to set up cfam */

#define	FSI_INIT_CLOCKS		5000	/* Clock out any old data */

#define	FSI_INIT_CLOCKS		5000	/* Clock out any old data */

#define	FSI_GPIO_DPOLL_CLOCKS	50      /* < 21 will cause slave to hang */

#define	FSI_GPIO_EPOLL_CLOCKS	50      /* Number of clocks for E_POLL retry */

#define	FSI_GPIO_STD_DELAY	10	/* Standard GPIO delay in nS */

#define	FSI_GPIO_STD_DELAY	10	/* Standard GPIO delay in nS */

					/* todo: adjust down as low as */

					/* todo: adjust down as low as */

					/* possible or eliminate */

					/* possible or eliminate */

#define FSI_CRC_ERR_RETRIES	10



#define	FSI_GPIO_CMD_DPOLL      0x2

#define	FSI_GPIO_CMD_DPOLL      0x2

#define	FSI_GPIO_CMD_EPOLL      0x3

#define	FSI_GPIO_CMD_TERM	0x3f

#define	FSI_GPIO_CMD_TERM	0x3f

#define FSI_GPIO_CMD_ABS_AR	0x4

#define FSI_GPIO_CMD_ABS_AR	0x4

#define FSI_GPIO_CMD_REL_AR	0x5

#define FSI_GPIO_CMD_REL_AR	0x5

#define FSI_GPIO_CMD_SAME_AR	0x3	/* but only a 2-bit opcode... */

#define FSI_GPIO_CMD_SAME_AR	0x3	/* but only a 2-bit opcode... */







/* Slave responses */

#define	FSI_GPIO_DPOLL_CLOCKS	50      /* < 21 will cause slave to hang */

#define	FSI_GPIO_RESP_ACK	0	/* Success */



#define	FSI_GPIO_RESP_BUSY	1	/* Slave busy */

/* Bus errors */

#define	FSI_GPIO_ERR_BUSY	1	/* Slave stuck in busy state */

#define	FSI_GPIO_RESP_ERRA	2	/* Any (misc) Error */

#define	FSI_GPIO_RESP_ERRA	2	/* Any (misc) Error */

#define	FSI_GPIO_RESP_ERRC	3	/* Slave reports master CRC error */

#define	FSI_GPIO_RESP_ERRC	3	/* Slave reports master CRC error */

#define	FSI_GPIO_MTOE		4	/* Master time out error */

#define	FSI_GPIO_MTOE		4	/* Master time out error */
@@ -330,6 +333,16 @@ static void build_dpoll_command(struct fsi_gpio_msg *cmd, uint8_t slave_id) 
	msg_push_crc(cmd);

	msg_push_crc(cmd);

}

}





static void build_epoll_command(struct fsi_gpio_msg *cmd, uint8_t slave_id)

{

	cmd->bits = 0;

	cmd->msg = 0;



	msg_push_bits(cmd, slave_id, 2);

	msg_push_bits(cmd, FSI_GPIO_CMD_EPOLL, 3);

	msg_push_crc(cmd);

}



static void echo_delay(struct fsi_master_gpio *master)

static void echo_delay(struct fsi_master_gpio *master)

{

{

	set_sda_output(master, 1);

	set_sda_output(master, 1);
@@ -355,6 +368,12 @@ static void fsi_master_gpio_error(struct fsi_master_gpio *master, int error) 




}

}





/*

 * Note: callers rely specifically on this returning -EAGAIN for

 * a CRC error detected in the response. Use other error code

 * for other situations. It will be converted to something else

 * higher up the stack before it reaches userspace.

 */

static int read_one_response(struct fsi_master_gpio *master,

static int read_one_response(struct fsi_master_gpio *master,

		uint8_t data_size, struct fsi_gpio_msg *msgp, uint8_t *tagp)

		uint8_t data_size, struct fsi_gpio_msg *msgp, uint8_t *tagp)

{

{
@@ -379,7 +398,7 @@ static int read_one_response(struct fsi_master_gpio *master, 
			"Master time out waiting for response\n");

			"Master time out waiting for response\n");

		fsi_master_gpio_error(master, FSI_GPIO_MTOE);

		fsi_master_gpio_error(master, FSI_GPIO_MTOE);

		spin_unlock_irqrestore(&master->bit_lock, flags);

		spin_unlock_irqrestore(&master->bit_lock, flags);

		return -EIO;

		return -ETIMEDOUT;

	}

	}





	msg.bits = 0;

	msg.bits = 0;
@@ -405,7 +424,7 @@ static int read_one_response(struct fsi_master_gpio *master, 
	if (crc) {

	if (crc) {

		dev_dbg(master->dev, "ERR response CRC\n");

		dev_dbg(master->dev, "ERR response CRC\n");

		fsi_master_gpio_error(master, FSI_GPIO_CRC_INVAL);

		fsi_master_gpio_error(master, FSI_GPIO_CRC_INVAL);

		return -EIO;

		return -EAGAIN;

	}

	}





	if (msgp)

	if (msgp)
@@ -451,11 +470,33 @@ static int poll_for_response(struct fsi_master_gpio *master, 
	unsigned long flags;

	unsigned long flags;

	uint8_t tag;

	uint8_t tag;

	uint8_t *data_byte = data;

	uint8_t *data_byte = data;



	int crc_err_retries = 0;

retry:

retry:

	rc = read_one_response(master, size, &response, &tag);

	rc = read_one_response(master, size, &response, &tag);

	if (rc)



		return rc;

	/* Handle retries on CRC errors */

	if (rc == -EAGAIN) {

		/* Too many retries ? */

		if (crc_err_retries++ > FSI_CRC_ERR_RETRIES) {

			/*

			 * Pass it up as a -EIO otherwise upper level will retry

			 * the whole command which isn't what we want here.

			 */

			rc = -EIO;

			goto fail;

		}

		dev_dbg(master->dev,

			 "CRC error retry %d\n", crc_err_retries);

		trace_fsi_master_gpio_crc_rsp_error(master);

		build_epoll_command(&cmd, slave);

		spin_lock_irqsave(&master->bit_lock, flags);

		clock_zeros(master, FSI_GPIO_EPOLL_CLOCKS);

		serial_out(master, &cmd);

		echo_delay(master);

		spin_unlock_irqrestore(&master->bit_lock, flags);

		goto retry;

	} else if (rc)

		goto fail;





	switch (tag) {

	switch (tag) {

	case FSI_GPIO_RESP_ACK:

	case FSI_GPIO_RESP_ACK:
@@ -496,18 +537,21 @@ static int poll_for_response(struct fsi_master_gpio *master, 
		break;

		break;





	case FSI_GPIO_RESP_ERRA:

	case FSI_GPIO_RESP_ERRA:

	case FSI_GPIO_RESP_ERRC:

		dev_dbg(master->dev, "ERRA received: 0x%x\n", (int)response.msg);

		dev_dbg(master->dev, "ERR%c received: 0x%x\n",

			tag == FSI_GPIO_RESP_ERRA ? 'A' : 'C',

			(int)response.msg);

		fsi_master_gpio_error(master, response.msg);

		fsi_master_gpio_error(master, response.msg);

		rc = -EIO;

		rc = -EIO;

		break;

		break;

	case FSI_GPIO_RESP_ERRC:

		dev_dbg(master->dev, "ERRC received: 0x%x\n", (int)response.msg);

		fsi_master_gpio_error(master, response.msg);

		trace_fsi_master_gpio_crc_cmd_error(master);

		rc = -EAGAIN;

		break;

	}

	}





	if (busy_count > 0)

	if (busy_count > 0)

		trace_fsi_master_gpio_poll_response_busy(master, busy_count);

		trace_fsi_master_gpio_poll_response_busy(master, busy_count);



 fail:

	/* Clock the slave enough to be ready for next operation */

	/* Clock the slave enough to be ready for next operation */

	spin_lock_irqsave(&master->bit_lock, flags);

	spin_lock_irqsave(&master->bit_lock, flags);

	clock_zeros(master, FSI_GPIO_PRIME_SLAVE_CLOCKS);

	clock_zeros(master, FSI_GPIO_PRIME_SLAVE_CLOCKS);
@@ -536,11 +580,21 @@ static int send_request(struct fsi_master_gpio *master, 
static int fsi_master_gpio_xfer(struct fsi_master_gpio *master, uint8_t slave,

static int fsi_master_gpio_xfer(struct fsi_master_gpio *master, uint8_t slave,

		struct fsi_gpio_msg *cmd, size_t resp_len, void *resp)

		struct fsi_gpio_msg *cmd, size_t resp_len, void *resp)

{

{

	int rc;

	int rc = -EAGAIN, retries = 0;





	while ((retries++) < FSI_CRC_ERR_RETRIES) {

		rc = send_request(master, cmd);

		rc = send_request(master, cmd);

	if (!rc)

		if (rc)

			break;

		rc = poll_for_response(master, slave, resp_len, resp);

		rc = poll_for_response(master, slave, resp_len, resp);

		if (rc != -EAGAIN)

			break;

		rc = -EIO;

		dev_warn(master->dev, "ECRC retry %d\n", retries);



		/* Pace it a bit before retry */

		msleep(1);

	}





	return rc;

	return rc;

}

}

include/trace/events/fsi_master_gpio.h

+27 −0
Original line number Original line Diff line number Diff line
@@ -64,6 +64,33 @@ TRACE_EVENT(fsi_master_gpio_break, 
	)

	)

);

);





TRACE_EVENT(fsi_master_gpio_crc_cmd_error,

	TP_PROTO(const struct fsi_master_gpio *master),

	TP_ARGS(master),

	TP_STRUCT__entry(

		__field(int,	master_idx)

	),

	TP_fast_assign(

		__entry->master_idx = master->master.idx;

	),

	TP_printk("fsi-gpio%d ----CRC command retry---",

		__entry->master_idx

	)

);



TRACE_EVENT(fsi_master_gpio_crc_rsp_error,

	TP_PROTO(const struct fsi_master_gpio *master),

	TP_ARGS(master),

	TP_STRUCT__entry(

		__field(int,	master_idx)

	),

	TP_fast_assign(

		__entry->master_idx = master->master.idx;

	),

	TP_printk("fsi-gpio%d ----CRC response---",

		__entry->master_idx

	)

);





TRACE_EVENT(fsi_master_gpio_poll_response_busy,

TRACE_EVENT(fsi_master_gpio_poll_response_busy,

	TP_PROTO(const struct fsi_master_gpio *master, int busy),

	TP_PROTO(const struct fsi_master_gpio *master, int busy),