[PATCH 5/5] realtek: restructure rtl_table_read/write

[Jan Hoffmann]

These two functions are identical apart from writing different values to
the read/write bit. Create a new function rtl_table_exec to reduce code
duplication.

Also replace the unbounded busy-waiting loop. As the hardware usually
responds very quickly, always call cond_resched, so that callers do not
need to worry about blocking for too long. This is especially important
for the L2 table, as a full loop (as in rtl83xx_port_fdb_dump) takes
about 20ms on RTL839x (and that function actually ends up being called
in a loop for every port).

So far, polling timeout errors are only handled by logging an error, but
a return value is added to allow proper handling in the future.

Signed-off-by: Jan Hoffmann <jan at 3e8.eu>
---

I'm not really sure if putting cond_resched in this place is really the
best solution. An alternative would be to place it directly in the loops
(i.e. rtl83xx_port_fdb_dump and l2_table_show) instead.

About error handling: Actually implementing that for all calls is going
to require large changes. And doing it in a proper way which is better
than just printing an error (i.e. actually trying to leave a consistent
state) is non-trivial. I started to work on that only for fdb/mdb
access, but that is only a part of where these tables are used:

https://github.com/janh/openwrt/commit/e45403299208d49675a0403ad94349ebdff2a374
https://github.com/janh/openwrt/commit/fa68b23cab542683832696f039cf160b96da83db
https://github.com/janh/openwrt/commit/92abfc2e4925e5bc1a0e25e464ca1d08833c9b30

 .../drivers/net/dsa/rtl83xx/common.c          | 47 ++++++++++++++-----
 .../drivers/net/dsa/rtl83xx/rtl83xx.h         |  4 +-
 2 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/common.c b/target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/common.c
index 13e63a5f0c5d..5e7c65247fc0 100644
--- a/target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/common.c
+++ b/target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/common.c
@@ -121,28 +121,51 @@ void rtl_table_release(struct table_reg *r)
 //	pr_info("Unlock done\n");
 }
 
+static int rtl_table_exec(struct table_reg *r, bool is_write, int idx)
+{
+	int ret = 0;
+	u32 cmd, val;
+
+	/* Read/write bit has inverted meaning on RTL838x */
+	if (r->rmode)
+		cmd = is_write ? 0 : BIT(r->c_bit);
+	else
+		cmd = is_write ? BIT(r->c_bit) : 0;
+
+	cmd |= BIT(r->c_bit + 1); /* Execute bit */
+	cmd |= r->tbl << r->t_bit; /* Table type */
+	cmd |= idx & (BIT(r->t_bit) - 1); /* Index */
+
+	sw_w32(cmd, r->addr);
+
+	/* The hardware typically responds immediately, so make sure that
+	 * other tasks always get a chance to run even if this function is
+	 * called in a loop.
+	 */
+	cond_resched();
+
+	ret = readx_poll_timeout(sw_r32, r->addr, val,
+				 !(val & BIT(r->c_bit + 1)), 20, 10000);
+	if (ret)
+		pr_err("%s: timeout\n", __func__);
+
+	return ret;
+}
+
 /*
  * Reads table index idx into the data registers of the table
  */
-void rtl_table_read(struct table_reg *r, int idx)
+int rtl_table_read(struct table_reg *r, int idx)
 {
-	u32 cmd = r->rmode ? BIT(r->c_bit) : 0;
-
-	cmd |= BIT(r->c_bit + 1) | (r->tbl << r->t_bit) | (idx & (BIT(r->t_bit) - 1));
-	sw_w32(cmd, r->addr);
-	do { } while (sw_r32(r->addr) & BIT(r->c_bit + 1));
+	return rtl_table_exec(r, false, idx);
 }
 
 /*
  * Writes the content of the table data registers into the table at index idx
  */
-void rtl_table_write(struct table_reg *r, int idx)
+int rtl_table_write(struct table_reg *r, int idx)
 {
-	u32 cmd = r->rmode ? 0 : BIT(r->c_bit);
-
-	cmd |= BIT(r->c_bit + 1) | (r->tbl << r->t_bit) | (idx & (BIT(r->t_bit) - 1));
-	sw_w32(cmd, r->addr);
-	do { } while (sw_r32(r->addr) & BIT(r->c_bit + 1));
+	return rtl_table_exec(r, true, idx);
 }
 
 /*
diff --git a/target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/rtl83xx.h b/target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/rtl83xx.h
index 107016469c69..485d0e8a7e9c 100644
--- a/target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/rtl83xx.h
+++ b/target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/rtl83xx.h
@@ -67,8 +67,8 @@ typedef enum {
 void rtl_table_init(void);
 struct table_reg *rtl_table_get(rtl838x_tbl_reg_t r, int t);
 void rtl_table_release(struct table_reg *r);
-void rtl_table_read(struct table_reg *r, int idx);
-void rtl_table_write(struct table_reg *r, int idx);
+int rtl_table_read(struct table_reg *r, int idx);
+int rtl_table_write(struct table_reg *r, int idx);
 inline u16 rtl_table_data(struct table_reg *r, int i);
 inline u32 rtl_table_data_r(struct table_reg *r, int i);
 inline void rtl_table_data_w(struct table_reg *r, u32 v, int i);
-- 
2.37.3