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* [PATCH] mci: add hint on how to resolve warning about vmmc-supply
@ 2022-07-24  6:39 Ahmad Fatoum
  0 siblings, 0 replies; only message in thread
From: Ahmad Fatoum @ 2022-07-24  6:39 UTC (permalink / raw)
  To: barebox; +Cc: Ahmad Fatoum

For legacy reasons, we do not fail the MCI registration when a regulator
can't be immediately requested, but we at least print a warning when
this happens. Add a comment guiding the user into how to resolve the

Signed-off-by: Ahmad Fatoum <>
 drivers/mci/mci-core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
index b8f71e15986e..8c08a4f61f63 100644
--- a/drivers/mci/mci-core.c
+++ b/drivers/mci/mci-core.c
@@ -1941,6 +1941,16 @@ int mci_register(struct mci_host *host)
 	host->supply = regulator_get(hw_dev, "vmmc");
 	if (IS_ERR(host->supply)) {
+		/*
+		 * If you know your regulator to be always online on boot, but
+		 * can't easily add a barebox driver for it, you may use
+		 * barebox,allow-dummy-supply in your board's regulator device
+		 * tree node to side step this warning.
+		 *
+		 * If you run into this warning, because your regulator driver
+		 * hasn't probed the device yet, consider enabling deep probe
+		 * for your board, to probe dependencies on demand.
+		 */
 		dev_warn(hw_dev, "Failed to get 'vmmc' regulator (ignored).\n");
 		host->supply = NULL;

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2022-07-24  6:39 [PATCH] mci: add hint on how to resolve warning about vmmc-supply Ahmad Fatoum

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