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Subject[PATCH v6 17/23] drivers/fsi: Add error handling for slave communication errors
Date
From: Jeremy Kerr <jk@ozlabs.org>

This change implements error handling in the FSI core, by cleaning up
and retrying failed operations, using the SISC, TERM and BREAK
facilities.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Chris Bostic <cbostic@linux.vnet.ibm.com>
---
drivers/fsi/fsi-core.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 114 insertions(+), 7 deletions(-)

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index 09becec..747d0e3 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -44,7 +44,9 @@
/*
* FSI slave engine control register offsets
*/
-#define FSI_SMODE 0x0 /* R/W: Mode register */
+#define FSI_SMODE 0x0 /* R/W: Mode register */
+#define FSI_SISC 0x8 /* R/W: Interrupt condition */
+#define FSI_SSTAT 0x14 /* R : Slave status */

/*
* SMODE fields
@@ -75,10 +77,14 @@ struct fsi_slave {
#define to_fsi_master(d) container_of(d, struct fsi_master, dev)
#define to_fsi_slave(d) container_of(d, struct fsi_slave, dev)

+static const int slave_retries = 2;
+static int discard_errors;
+
static int fsi_master_read(struct fsi_master *master, int link,
uint8_t slave_id, uint32_t addr, void *val, size_t size);
static int fsi_master_write(struct fsi_master *master, int link,
uint8_t slave_id, uint32_t addr, const void *val, size_t size);
+static int fsi_master_break(struct fsi_master *master, int link);

/* FSI endpoint-device support */

@@ -180,32 +186,131 @@ static int fsi_slave_calc_addr(struct fsi_slave *slave, uint32_t *addrp,
return 0;
}

+int fsi_slave_report_and_clear_errors(struct fsi_slave *slave)
+{
+ struct fsi_master *master = slave->master;
+ uint32_t irq, stat;
+ int rc, link;
+ uint8_t id;
+
+ link = slave->link;
+ id = slave->id;
+
+ rc = fsi_master_read(master, link, id, FSI_SLAVE_BASE + FSI_SISC,
+ &irq, sizeof(irq));
+ if (rc)
+ return rc;
+
+ rc = fsi_master_read(master, link, id, FSI_SLAVE_BASE + FSI_SSTAT,
+ &stat, sizeof(stat));
+ if (rc)
+ return rc;
+
+ dev_info(&slave->dev, "status: 0x%08x, sisc: 0x%08x\n",
+ be32_to_cpu(stat), be32_to_cpu(irq));
+
+ /* clear interrupts */
+ return fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SISC,
+ &irq, sizeof(irq));
+}
+
+static int fsi_slave_set_smode(struct fsi_master *master, int link, int id);
+
+int fsi_slave_handle_error(struct fsi_slave *slave, bool write, uint32_t addr,
+ size_t size)
+{
+ struct fsi_master *master = slave->master;
+ int rc, link;
+ uint32_t reg;
+ uint8_t id;
+
+ if (discard_errors)
+ return -1;
+
+ link = slave->link;
+ id = slave->id;
+
+ dev_dbg(&slave->dev, "handling error on %s to 0x%08x[%zd]",
+ write ? "write" : "read", addr, size);
+
+ /* try a simple clear of error conditions, which may fail if we've lost
+ * communication with the slave
+ */
+ rc = fsi_slave_report_and_clear_errors(slave);
+ if (!rc)
+ return 0;
+
+ /* send a TERM and retry */
+ if (master->term) {
+ rc = master->term(master, link, id);
+ if (!rc) {
+ rc = fsi_master_read(master, link, id, 0,
+ &reg, sizeof(reg));
+ if (!rc)
+ rc = fsi_slave_report_and_clear_errors(slave);
+ if (!rc)
+ return 0;
+ }
+ }
+
+ /* getting serious, reset the slave via BREAK */
+ rc = fsi_master_break(master, link);
+ if (rc)
+ return rc;
+
+ rc = fsi_slave_set_smode(master, link, id);
+ if (rc)
+ return rc;
+
+ return fsi_slave_report_and_clear_errors(slave);
+}
+
int fsi_slave_read(struct fsi_slave *slave, uint32_t addr,
void *val, size_t size)
{
uint8_t id = slave->id;
- int rc;
+ int rc, err_rc, i;

rc = fsi_slave_calc_addr(slave, &addr, &id);
if (rc)
return rc;

- return fsi_master_read(slave->master, slave->link, id,
- addr, val, size);
+ for (i = 0; i < slave_retries; i++) {
+ rc = fsi_master_read(slave->master, slave->link,
+ id, addr, val, size);
+ if (!rc)
+ break;
+
+ err_rc = fsi_slave_handle_error(slave, false, addr, size);
+ if (err_rc)
+ break;
+ }
+
+ return rc;
}

int fsi_slave_write(struct fsi_slave *slave, uint32_t addr,
const void *val, size_t size)
{
uint8_t id = slave->id;
- int rc;
+ int rc, err_rc, i;

rc = fsi_slave_calc_addr(slave, &addr, &id);
if (rc)
return rc;

- return fsi_master_write(slave->master, slave->link, id,
- addr, val, size);
+ for (i = 0; i < slave_retries; i++) {
+ rc = fsi_master_write(slave->master, slave->link,
+ id, addr, val, size);
+ if (!rc)
+ break;
+
+ err_rc = fsi_slave_handle_error(slave, true, addr, size);
+ if (err_rc)
+ break;
+ }
+
+ return rc;
}

extern int fsi_slave_claim_range(struct fsi_slave *slave,
@@ -765,3 +870,5 @@ static void fsi_exit(void)

module_init(fsi_init);
module_exit(fsi_exit);
+module_param(discard_errors, int, 0664);
+MODULE_PARM_DESC(discard_errors, "Don't invoke error handling on bus accesses");
--
1.8.2.2
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