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Diffstat (limited to 'Documentation/scsi/ufs.rst')
| -rw-r--r-- | Documentation/scsi/ufs.rst | 15 |
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diff --git a/Documentation/scsi/ufs.rst b/Documentation/scsi/ufs.rst index fbac745b783c..a7b2b2ed1c3a 100644 --- a/Documentation/scsi/ufs.rst +++ b/Documentation/scsi/ufs.rst @@ -17,6 +17,8 @@ Universal Flash Storage 3.2 UTP Transfer requests 3.3 UFS error handling 3.4 SCSI Error handling + 4. BSG Support + 5. UFS Reference Clock Frequency configuration 1. Overview @@ -193,3 +195,16 @@ UFS specifications can be found at: - UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf - UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf + +5. UFS Reference Clock Frequency configuration +============================================== + +Devicetree can define a clock named "ref_clk" under the UFS controller node +to specify the intended reference clock frequency for the UFS storage +parts. ACPI-based system can specify the frequency using ACPI +Device-Specific Data property named "ref-clk-freq". In both ways the value +is interpreted as frequency in Hz and must match one of the values given in +the UFS specification. UFS subsystem will attempt to read the value when +executing common controller initialization. If the value is available, UFS +subsystem will ensure the bRefClkFreq attribute of the UFS storage device is +set accordingly and will modify it if there is a mismatch. |