[PATCH v3 1/1] regmap: Synchronize cache for the page selector

[Andy Shevchenko]

If the selector register is represented in each page, its value
in accordance to the debugfs is stale because it gets synchronized
only after the real page switch happens. Synchronize cache for
the page selector.

Before (offset followed by hexdump, the first byte is selector):

    // Real registers
    18: 05 ff 00 00 ff 0f 00 00 f0 00 00 00
    ...
    // Virtual (per port)
    40: 05 ff 00 00 e0 e0 00 00 00 00 00 1f
    50: 00 ff 00 00 e0 e0 00 00 00 00 00 1f
    60: 01 ff 00 00 ff ff 00 00 00 00 00 00
    70: 02 ff 00 00 cf f3 00 00 00 00 00 0c
    80: 03 ff 00 00 00 00 00 00 00 00 00 ff
    90: 04 ff 00 00 ff 0f 00 00 f0 00 00 00

After:

    // Real registers
    18: 05 ff 00 00 ff 0f 00 00 f0 00 00 00
    ...
    // Virtual (per port)
    40: 00 ff 00 00 e0 e0 00 00 00 00 00 1f
    50: 01 ff 00 00 e0 e0 00 00 00 00 00 1f
    60: 02 ff 00 00 ff ff 00 00 00 00 00 00
    70: 03 ff 00 00 cf f3 00 00 00 00 00 0c
    80: 04 ff 00 00 00 00 00 00 00 00 00 ff
    90: 05 ff 00 00 ff 0f 00 00 f0 00 00 00

Fixes: 6863ca622759 ("regmap: Add support for register indirect addressing.")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
v3: rebased on the top of latest vanilla
 drivers/base/regmap/regmap.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index f2843f814675..197c79b66828 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1557,24 +1557,40 @@ static int _regmap_select_page(struct regmap *map, unsigned int *reg,
 			return -EINVAL;
 	}
 
-	/* It is possible to have selector register inside data window.
-	   In that case, selector register is located on every page and
-	   it needs no page switching, when accessed alone. */
+	/*
+	 * It is possible to have selector register inside data window.
+	 * In that case, selector register is located on every page and it
+	 * needs no page switching, when accessed alone.
+	 *
+	 * Nevertheless we should synchronize the cache values for it.
+	 */
 	if (val_num > 1 ||
 	    range->window_start + win_offset != range->selector_reg) {
+		unsigned int page_off = win_page * range->window_len;
+		unsigned int sel_offset = range->selector_reg - range->window_start;
+		unsigned int sel_register = range->range_min + page_off + sel_offset;
+		unsigned int val = win_page << range->selector_shift;
+		unsigned int mask = range->selector_mask;
+
 		/* Use separate work_buf during page switching */
 		orig_work_buf = map->work_buf;
 		map->work_buf = map->selector_work_buf;
 
-		ret = _regmap_update_bits(map, range->selector_reg,
-					  range->selector_mask,
-					  win_page << range->selector_shift,
+		ret = _regmap_update_bits(map, range->selector_reg, mask, val,
 					  &page_chg, false);
 
 		map->work_buf = orig_work_buf;
 
 		if (ret != 0)
 			return ret;
+
+		/*
+		 * If selector register has been just updated, update the respective
+		 * virtual copy as well.
+		 */
+		if (page_chg &&
+		    in_range(range->selector_reg, range->window_start, range->window_len))
+			_regmap_update_bits(map, sel_register, mask, val, NULL, false);
 	}
 
 	*reg = range->window_start + win_offset;
-- 
2.43.0.rc1.1336.g36b5255a03ac