scsi: hisi_sas: dt-bindings: add an property of signal attenuation

BugLink: https://bugs.launchpad.net/bugs/1768974
For some new boards with hip07 chipset we are required to set PHY config
registers differently. The hw property which determines how to set these
registers is in the PHY signal attenuation readings.

This patch add an devicetree property, "hisilicon,signal-attenuation", which
is used to describe the signal attenuation of an board.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
(cherry picked from commit 4c40db995eb54c3ee8cb5a8340640f49395d5f9e)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/Documentation/devicetree/bindings/scsi/hisilicon-sas.txt b/Documentation/devicetree/bindings/scsi/hisilicon-sas.txt
index b6a869f977152f37153cc871f4ac8fc7a4d84ba9..8248daf724b285e5f7fef20c930e21ce9a285173 100644 (file)
--- a/Documentation/devicetree/bindings/scsi/hisilicon-sas.txt
+++ b/Documentation/devicetree/bindings/scsi/hisilicon-sas.txt
@@ -50,6 +50,13 @@ Main node required properties:
 Optional main node properties:
  - hip06-sas-v2-quirk-amt : when set, indicates that the v2 controller has the
                            "am-max-transmissions" limitation.
+ - hisilicon,signal-attenuation : array of 3 32-bit values, containing de-emphasis,
+               preshoot, and boost attenuation readings for the board. They
+               are used to describe the signal attenuation of the board. These
+               values' range is 7600 to 12400, and used to represent -24dB to
+               24dB.
+               The formula is "y = (x-10000)/10000". For example, 10478
+               means 4.78dB.
 
 Example:
        sas0: sas@c1000000 {