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Subject[PATCH] drm/bridge: fix stack usage warning on old gcc
Date
Some older versions of gcc badly optimize code that passes
an inline function argument into another function by reference,
causing huge stack usage:

drivers/gpu/drm/bridge/tc358768.c: In function 'tc358768_bridge_pre_enable':
drivers/gpu/drm/bridge/tc358768.c:840:1: error: the frame size of 2256 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]

Use a temporary variable as a workaround and add a comment pointing
to the gcc bug.

Fixes: ff1ca6397b1d ("drm/bridge: Add tc358768 driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/gpu/drm/bridge/tc358768.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
index 1b39e8d37834..6650fe4cfc20 100644
--- a/drivers/gpu/drm/bridge/tc358768.c
+++ b/drivers/gpu/drm/bridge/tc358768.c
@@ -178,6 +178,8 @@ static int tc358768_clear_error(struct tc358768_priv *priv)

static void tc358768_write(struct tc358768_priv *priv, u32 reg, u32 val)
{
+ /* work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+ int tmpval = val;
size_t count = 2;

if (priv->error)
@@ -187,7 +189,7 @@ static void tc358768_write(struct tc358768_priv *priv, u32 reg, u32 val)
if (reg < 0x100 || reg >= 0x600)
count = 1;

- priv->error = regmap_bulk_write(priv->regmap, reg, &val, count);
+ priv->error = regmap_bulk_write(priv->regmap, reg, &tmpval, count);
}

static void tc358768_read(struct tc358768_priv *priv, u32 reg, u32 *val)
--
2.26.0
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