[PATCH] drm: panel: fix excessive stack usage in td028ttec1_prepare

From: Arnd Bergmann
Date: Tue Jan 07 2020 - 16:28:15 EST

With gcc -O3, the compiler can inline very aggressively,
leading to rather large stack usage:

drivers/gpu/drm/panel/panel-tpo-td028ttec1.c: In function 'td028ttec1_prepare':
drivers/gpu/drm/panel/panel-tpo-td028ttec1.c:233:1: error: the frame size of 2768 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]

Marking jbt_reg_write_1() as noinline avoids the case where
multiple instances of this function get inlined into the same
stack frame and each one adds a copy of 'tx_buf'.

Fixes: mmtom ("init/Kconfig: enable -O3 for all arches")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
drivers/gpu/drm/panel/panel-tpo-td028ttec1.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/panel-tpo-td028ttec1.c b/drivers/gpu/drm/panel/panel-tpo-td028ttec1.c
index cf29405a2dbe..17ee5e87141f 100644
--- a/drivers/gpu/drm/panel/panel-tpo-td028ttec1.c
+++ b/drivers/gpu/drm/panel/panel-tpo-td028ttec1.c
@@ -105,7 +105,7 @@ static int jbt_ret_write_0(struct td028ttec1_panel *lcd, u8 reg, int *err)
return ret;

-static int jbt_reg_write_1(struct td028ttec1_panel *lcd,
+static int noinline_for_stack jbt_reg_write_1(struct td028ttec1_panel *lcd,
u8 reg, u8 data, int *err)
struct spi_device *spi = lcd->spi;