[RFC PATCH] drm/bridge: adv7511: use cache_only during power down

[phucduc . bui]

From: bui duc phuc <phucduc.bui@xxxxxxxxx>

adv7511_power_on() and adv7511_power_off() restore the register state
using regcache_mark_dirty() and regcache_sync(), but nothing prevents
other code paths from accessing the registers over I2C while the chip
is powered down.
Wrap the power-down window with regcache_cache_only() to prevent direct
register accesses. It is unclear whether this is necessary or whether
it could affect the CEC or packet sub-regmaps, so send this as an RFC.

Signed-off-by: bui duc phuc <phucduc.bui@xxxxxxxxx>
---

This RFC is related to the following patch series:
https://lore.kernel.org/all/20260724100803.50169-1-phucduc.bui@xxxxxxxxx/

 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
index 3e470366bce0..49da1806797b 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -323,6 +323,7 @@ static void adv7511_power_off(struct adv7511 *adv7511)
 	__adv7511_power_off(adv7511);
 	if (adv7511->info->has_dsi)
 		adv7533_dsi_power_off(adv7511);
+	regcache_cache_only(adv7511->regmap, true);
 	adv7511->powered = false;
 }
 
@@ -374,11 +375,13 @@ static void adv7511_power_on(struct adv7511 *adv7511)
 	/*
 	 * Most of the registers are reset during power down or when HPD is low.
 	 */
+	regcache_cache_only(adv7511->regmap, false);
 	ret = regcache_sync(adv7511->regmap);
 	if (ret) {
 		dev_err(&adv7511->i2c_main->dev,
 			"Failed to sync register cache: %d\n", ret);
 		__adv7511_power_off(adv7511);
+		regcache_cache_only(adv7511->regmap, true);
 		return;
 	}
 
-- 
2.43.0