On Tue, May 05, 2020 at 04:01:16PM +0200, Arnd Bergmann wrote:
> 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 <a...@arndb.de>
Reviewed-by: Nathan Chancellor <natechancel...@gmail.com>
> ---
> 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 0f1547f09d08..72f5c7b30079 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)) {
> --
> 2.26.0
>
