scsi: ufs: set the device reference clock setting

UFS host supplies the reference clock to UFS device and UFS device
specification allows host to provide one of the 4 frequencies (19.2 MHz, 26
MHz, 38.4 MHz, 52 MHz) for reference clock. Host should set the device
reference clock frequency setting in the device based on what frequency it
is supplying to UFS device.

Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
Reviewed-by: Evan Green <evgreen@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
index 2df00524bd21..8cf59452c675 100644
--- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
+++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
@@ -33,6 +33,12 @@ Optional properties:
 - clocks                : List of phandle and clock specifier pairs
 - clock-names           : List of clock input name strings sorted in the same
                           order as the clocks property.
+			  "ref_clk" indicates reference clock frequency.
+			  UFS host supplies reference clock to UFS device and UFS device
+			  specification allows host to provide one of the 4 frequencies (19.2 MHz,
+			  26 MHz, 38.4 MHz, 52MHz) for reference clock. This "ref_clk" entry is
+			  parsed and used to update the reference clock setting in device.
+			  Defaults to 26 MHz(as per specification) if not specified by host.
 - freq-table-hz		: Array of <min max> operating frequencies stored in the same
                           order as the clocks property. If this property is not
 			  defined or a value in the array is "0" then it is assumed