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SubjectRe: [PATCH 3/3] mtd: mtdconcat: add suspend lock handling
On Mon, 11 Oct 2021 13:52:53 +0200
Sean Nyekjaer <sean@geanix.com> wrote:

> Use new suspend lock handling for this special case for concatenated
> MTD devices.
>
> Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
> Signed-off-by: Sean Nyekjaer <sean@geanix.com>
> ---
> drivers/mtd/mtdconcat.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
> index f685a581df48..c497c851481f 100644
> --- a/drivers/mtd/mtdconcat.c
> +++ b/drivers/mtd/mtdconcat.c
> @@ -561,25 +561,32 @@ static void concat_sync(struct mtd_info *mtd)
>
> static int concat_suspend(struct mtd_info *mtd)
> {
> + struct mtd_info *master = mtd_get_master(mtd);
> struct mtd_concat *concat = CONCAT(mtd);
> int i, rc = 0;
>
> for (i = 0; i < concat->num_subdev; i++) {
> struct mtd_info *subdev = concat->subdev[i];
> - if ((rc = mtd_suspend(subdev)) < 0)
> +
> + down_write(&master->master.suspend_lock);
> + if ((rc = __mtd_suspend(subdev)) < 0)
> return rc;
> + up_write(&master->master.suspend_lock);
> }
> return rc;
> }
>
> static void concat_resume(struct mtd_info *mtd)
> {
> + struct mtd_info *master = mtd_get_master(mtd);
> struct mtd_concat *concat = CONCAT(mtd);
> int i;
>
> for (i = 0; i < concat->num_subdev; i++) {
> struct mtd_info *subdev = concat->subdev[i];
> - mtd_resume(subdev);
> + down_write(&master->master.suspend_lock);
> + __mtd_resume(subdev);
> + up_write(&master->master.suspend_lock);
> }
> }
>

Why do we need to implement the _suspend/_resume() hooks here? The
underlying MTD devices should be suspended at some point (when the
class ->suspend() method is called on those device), and there's
nothing mtdconcat-specific to do here. Looks like implementing this
suspend-all-subdevs loop results in calling mtd->_suspend()/_resume()
twice, which is useless. The only issue I see is if the subdevices
haven't been registered to the device model, but that happens, I
believe we have bigger issues (those devices won't be suspended when
mtdconcat is not used).

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