mmc: warn about voltage mismatches

Get rid of a silent failure mode when the MMC/SD host doesn't
support the voltages needed to operate a given card, by
adding a warning.  A 3.3V host and a 3.0V card, for example,
no longer need to mysteriously just not work at all.

This isn't the best diagnostic; ideally it would also tell
what voltage the card and host support (and not just by
dumping the bitmasks).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 5f288aeeb721..df6ce4a06cf3 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -542,6 +542,8 @@ u32 mmc_select_voltage(struct mmc_host *host, u32 ocr)
                 host->ios.vdd = bit;
                 mmc_set_ios(host);
         } else {
+                pr_warning("%s: host doesn't support card's voltages\n",
+                                mmc_hostname(host));
                 ocr = 0;
         }