Commit 3e1b6469 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Miquel Raynal
Browse files

mtd: lpddr: fix excessive stack usage with clang 



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: 96ba9dd6 ("mtd: lpddr: add driver for LPDDR2-NVM PCM memories")
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Reviewed-by: default avatarNathan Chancellor <natechancellor@gmail.com>
Acked-by: default avatarMiquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: default avatarMiquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200505140136.263461-1-arnd@arndb.de
parent 1d0e5ebf

drivers/mtd/lpddr/lpddr2_nvm.c

+19 −16
Original line number Diff line number Diff line
@@ -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)) {

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