[PATCH linux dev-4.13 03/10] fsi/fsi-master-gpio: Implement CRC error recovery
Benjamin Herrenschmidt
benh at kernel.crashing.org
Thu May 24 15:14:22 AEST 2018
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: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
Note: This was actually tested by removing some of my fixes, thus
causing us to hit occasional CRC errors during high LPC activity.
---
drivers/fsi/fsi-master-gpio.c | 90 ++++++++++++++++++++------
include/trace/events/fsi_master_gpio.h | 27 ++++++++
2 files changed, 99 insertions(+), 18 deletions(-)
diff --git a/drivers/fsi/fsi-master-gpio.c b/drivers/fsi/fsi-master-gpio.c
index 0a6799bda294..351c12f2ac55 100644
--- a/drivers/fsi/fsi-master-gpio.c
+++ b/drivers/fsi/fsi-master-gpio.c
@@ -22,20 +22,23 @@
#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_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 */
/* todo: adjust down as low as */
/* possible or eliminate */
+#define FSI_CRC_ERR_RETRIES 10
+
#define FSI_GPIO_CMD_DPOLL 0x2
+#define FSI_GPIO_CMD_EPOLL 0x3
#define FSI_GPIO_CMD_TERM 0x3f
#define FSI_GPIO_CMD_ABS_AR 0x4
#define FSI_GPIO_CMD_REL_AR 0x5
#define FSI_GPIO_CMD_SAME_AR 0x3 /* but only a 2-bit opcode... */
-
-#define FSI_GPIO_DPOLL_CLOCKS 50 /* < 21 will cause slave to hang */
-
-/* Bus errors */
-#define FSI_GPIO_ERR_BUSY 1 /* Slave stuck in busy state */
+/* Slave responses */
+#define FSI_GPIO_RESP_ACK 0 /* Success */
+#define FSI_GPIO_RESP_BUSY 1 /* Slave busy */
#define FSI_GPIO_RESP_ERRA 2 /* Any (misc) Error */
#define FSI_GPIO_RESP_ERRC 3 /* Slave reports master CRC 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);
}
+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)
{
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,
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");
fsi_master_gpio_error(master, FSI_GPIO_MTOE);
spin_unlock_irqrestore(&master->bit_lock, flags);
- return -EIO;
+ return -ETIMEDOUT;
}
msg.bits = 0;
@@ -405,7 +424,7 @@ static int read_one_response(struct fsi_master_gpio *master,
if (crc) {
dev_dbg(master->dev, "ERR response CRC\n");
fsi_master_gpio_error(master, FSI_GPIO_CRC_INVAL);
- return -EIO;
+ return -EAGAIN;
}
if (msgp)
@@ -451,11 +470,33 @@ static int poll_for_response(struct fsi_master_gpio *master,
unsigned long flags;
uint8_t tag;
uint8_t *data_byte = data;
-
+ int crc_err_retries = 0;
retry:
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) {
case FSI_GPIO_RESP_ACK:
@@ -496,18 +537,21 @@ static int poll_for_response(struct fsi_master_gpio *master,
break;
case FSI_GPIO_RESP_ERRA:
- case FSI_GPIO_RESP_ERRC:
- dev_dbg(master->dev, "ERR%c received: 0x%x\n",
- tag == FSI_GPIO_RESP_ERRA ? 'A' : 'C',
- (int)response.msg);
+ dev_dbg(master->dev, "ERRA received: 0x%x\n", (int)response.msg);
fsi_master_gpio_error(master, response.msg);
rc = -EIO;
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)
trace_fsi_master_gpio_poll_response_busy(master, busy_count);
-
+ fail:
/* Clock the slave enough to be ready for next operation */
spin_lock_irqsave(&master->bit_lock, flags);
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,
struct fsi_gpio_msg *cmd, size_t resp_len, void *resp)
{
- int rc;
+ int rc = -EAGAIN, retries = 0;
- rc = send_request(master, cmd);
- if (!rc)
+ while ((retries++) < FSI_CRC_ERR_RETRIES) {
+ rc = send_request(master, cmd);
+ if (rc)
+ break;
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;
}
diff --git a/include/trace/events/fsi_master_gpio.h b/include/trace/events/fsi_master_gpio.h
index 48e83e5755f4..e18b94ce85b2 100644
--- a/include/trace/events/fsi_master_gpio.h
+++ b/include/trace/events/fsi_master_gpio.h
@@ -63,6 +63,33 @@ 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,
TP_PROTO(const struct fsi_master_gpio *master, int busy),
--
2.17.0
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