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usb: typec: ucsi: Wait 20ms before reading CCI after a reset

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The PPM might take time to process a reset. Allow 20ms for the reset to
be processed before reading the CCI.

This should not slow down existing implementations because they would
not set any bits in the CCI after a reset, and would take a 20ms delay
to read the CCI anyway. This change makes the delay explicit, and
reduces a CCI read. Based on the spec, the PPM has 10ms to set busy, so,
20ms seems like a reasonable delay before we read the CCI.

Signed-off-by: Pavan Holla <pholla@chromium.org>
Reviewed-by: Prashant Malani <pmalani@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20240409-ucsi-reset-delay-v3-1-8440710b012b@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavan Holla
2024-04-09 01:58:57 +00:00
committed by Greg Kroah-Hartman
parent 0fb782b5d5
commit c4ede56172
1 changed files with 3 additions and 1 deletions
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4
drivers/usb/typec/ucsi/ucsi.c
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@@ -1337,6 +1337,9 @@ static int ucsi_reset_ppm(struct ucsi *ucsi)
goto out;
}
/* Give the PPM time to process a reset before reading CCI */
msleep(20);
ret = ucsi->ops->read(ucsi, UCSI_CCI, &cci, sizeof(cci));
if (ret)
goto out;
@@ -1350,7 +1353,6 @@ static int ucsi_reset_ppm(struct ucsi *ucsi)
goto out;
}
msleep(20);
} while (!(cci & UCSI_CCI_RESET_COMPLETE));
out: