linux-kernel - [PATCH v3 3/3] drm/bridge: tc358767: Support write-only registers

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Message-Id: <20240904120546.1845856-4-alexander.stein@ew.tq-group.com>
Date: Wed,  4 Sep 2024 14:05:45 +0200
From: Alexander Stein <alexander.stein@...tq-group.com>
To: Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
Cc: Alexander Stein <alexander.stein@...tq-group.com>,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 3/3] drm/bridge: tc358767: Support write-only registers

Most registers are read-writable, but some are only RO or even WO.
regmap does not support using readable_reg and wr_table when outputting
in debugfs, so switch to writeable_reg.
First check for RO or WO registers and fallback tc_readable_reg() for the
leftover RW registers.

Signed-off-by: Alexander Stein <alexander.stein@...tq-group.com>
Reviewed-by: Robert Foss <rfoss@...nel.org>
---
 drivers/gpu/drm/bridge/tc358767.c | 40 ++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
index 1c42c8c6e632e..159c95b26d33c 100644
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -2169,19 +2169,31 @@ static const struct regmap_access_table tc_precious_table = {
 	.n_yes_ranges = ARRAY_SIZE(tc_precious_ranges),
 };
 
-static const struct regmap_range tc_non_writeable_ranges[] = {
-	regmap_reg_range(PPI_BUSYPPI, PPI_BUSYPPI),
-	regmap_reg_range(DSI_BUSYDSI, DSI_BUSYDSI),
-	regmap_reg_range(DSI_LANESTATUS0, DSI_INTSTATUS),
-	regmap_reg_range(TC_IDREG, SYSSTAT),
-	regmap_reg_range(GPIOI, GPIOI),
-	regmap_reg_range(DP0_LTSTAT, DP0_SNKLTCHGREQ),
-};
-
-static const struct regmap_access_table tc_writeable_table = {
-	.no_ranges = tc_non_writeable_ranges,
-	.n_no_ranges = ARRAY_SIZE(tc_non_writeable_ranges),
-};
+static bool tc_writeable_reg(struct device *dev, unsigned int reg)
+{
+	/* RO reg */
+	switch (reg) {
+	case PPI_BUSYPPI:
+	case DSI_BUSYDSI:
+	case DSI_LANESTATUS0:
+	case DSI_LANESTATUS1:
+	case DSI_INTSTATUS:
+	case TC_IDREG:
+	case SYSBOOT:
+	case SYSSTAT:
+	case GPIOI:
+	case DP0_LTSTAT:
+	case DP0_SNKLTCHGREQ:
+		return false;
+	}
+	/* WO reg */
+	switch (reg) {
+	case DSI_STARTDSI:
+	case DSI_INTCLR:
+		return true;
+	}
+	return tc_readable_reg(dev, reg);
+}
 
 static const struct regmap_config tc_regmap_config = {
 	.name = "tc358767",
@@ -2191,9 +2203,9 @@ static const struct regmap_config tc_regmap_config = {
 	.max_register = PLL_DBG,
 	.cache_type = REGCACHE_MAPLE,
 	.readable_reg = tc_readable_reg,
+	.writeable_reg = tc_writeable_reg,
 	.volatile_table = &tc_volatile_table,
 	.precious_table = &tc_precious_table,
-	.wr_table = &tc_writeable_table,
 	.reg_format_endian = REGMAP_ENDIAN_BIG,
 	.val_format_endian = REGMAP_ENDIAN_LITTLE,
 };
-- 
2.34.1