linux-kernel - [PATCH] drm: panel: fix excessive stack usage in td028ttec1

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Message-Id: <20200107212747.4182515-1-arnd@arndb.de>
Date:   Tue,  7 Jan 2020 22:27:33 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Oleksandr Natalenko <oleksandr@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Sam Ravnborg <sam@...nborg.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm: panel: fix excessive stack usage in td028ttec1_prepare

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@...db.de>
---
 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;
-- 
2.20.0