[PATCH 5.8 331/633] mtd: lpddr: fix excessive stack usage with clang

Greg Kroah-Hartman
2020-10-27T15:10:23Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 3e1b6469f8324bee5927b063e2aca30d3e56b907 ]

Building lpddr2_nvm with clang can result in a giant stack usage
in one function:

drivers/mtd/lpddr/lpddr2_nvm.c:399:12: error: stack frame size of 1144 bytes in function 'lpddr2_nvm_probe' [-Werror,-Wframe-larger-than=]

The problem is that clang decides to build a copy of the mtd_info
structure on the stack and then do a memcpy() into the actual version. It
shouldn't really do it that way, but it's not strictly a bug either.

As a workaround, use a static const version of the structure to assign
most of the members upfront and then only set the few members that
require runtime knowledge at probe time.

Fixes: 96ba9dd65788 ("mtd: lpddr: add driver for LPDDR2-NVM PCM memories")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200505140136.263461-1-arnd@arndb.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/mtd/lpddr/lpddr2_nvm.c | 35 ++++++++++++++++++----------------
1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/drivers/mtd/lpddr/lpddr2_nvm.c b/drivers/mtd/lpddr/lpddr2_nvm.c
index 0f1547f09d08b..72f5c7b300790 100644
--- a/drivers/mtd/lpddr/lpddr2_nvm.c
+++ b/drivers/mtd/lpddr/lpddr2_nvm.c
@@ -393,6 +393,17 @@ static int lpddr2_nvm_lock(struct mtd_info *mtd, loff_t start_add,
return lpddr2_nvm_do_block_op(mtd, start_add, len, LPDDR2_NVM_LOCK);
}

+static const struct mtd_info lpddr2_nvm_mtd_info = {
+ .type = MTD_RAM,
+ .writesize = 1,
+ .flags = (MTD_CAP_NVRAM | MTD_POWERUP_LOCK),
+ ._read = lpddr2_nvm_read,
+ ._write = lpddr2_nvm_write,
+ ._erase = lpddr2_nvm_erase,
+ ._unlock = lpddr2_nvm_unlock,
+ ._lock = lpddr2_nvm_lock,
+};
+
/*
* lpddr2_nvm driver probe method
*/
@@ -433,6 +444,7 @@ static int lpddr2_nvm_probe(struct platform_device *pdev)
.pfow_base = OW_BASE_ADDRESS,
.fldrv_priv = pcm_data,
};
+
if (IS_ERR(map->virt))
return PTR_ERR(map->virt);

@@ -444,22 +456,13 @@ static int lpddr2_nvm_probe(struct platform_device *pdev)
return PTR_ERR(pcm_data->ctl_regs);

/* Populate mtd_info data structure */
- *mtd = (struct mtd_info) {
- .dev = { .parent = &pdev->dev },
- .name = pdev->dev.init_name,
- .type = MTD_RAM,
- .priv = map,
- .size = resource_size(add_range),
- .erasesize = ERASE_BLOCKSIZE * pcm_data->bus_width,
- .writesize = 1,
- .writebufsize = WRITE_BUFFSIZE * pcm_data->bus_width,
- .flags = (MTD_CAP_NVRAM | MTD_POWERUP_LOCK),
- ._read = lpddr2_nvm_read,
- ._write = lpddr2_nvm_write,
- ._erase = lpddr2_nvm_erase,
- ._unlock = lpddr2_nvm_unlock,
- ._lock = lpddr2_nvm_lock,
- };
+ *mtd = lpddr2_nvm_mtd_info;
+ mtd->dev.parent = &pdev->dev;
+ mtd->name = pdev->dev.init_name;
+ mtd->priv = map;
+ mtd->size = resource_size(add_range);
+ mtd->erasesize = ERASE_BLOCKSIZE * pcm_data->bus_width;
+ mtd->writebufsize = WRITE_BUFFSIZE * pcm_data->bus_width;

/* Verify the presence of the device looking for PFOW string */
if (!lpddr2_nvm_pfow_present(map)) {
--
2.25.1