On Thu, Jun 14, 2018 at 5:33 AM, sayali <sayalil@xxxxxxxxxxxxxx> wrote: > Comment inline. > > Thanks, > Sayali > -----Original Message----- > From: Rob Herring [mailto:robh@xxxxxxxxxx] > Sent: Wednesday, June 13, 2018 12:57 AM > To: Sayali Lokhande <sayalil@xxxxxxxxxxxxxx> > Cc: subhashj@xxxxxxxxxxxxxx; cang@xxxxxxxxxxxxxx; > vivek.gautam@xxxxxxxxxxxxxx; rnayak@xxxxxxxxxxxxxx; vinholikatti@xxxxxxxxx; > jejb@xxxxxxxxxxxxxxxxxx; martin.petersen@xxxxxxxxxx; > asutoshd@xxxxxxxxxxxxxx; evgreen@xxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; > Mark Rutland <mark.rutland@xxxxxxx>; Mathieu Malaterre <malat@xxxxxxxxxx>; > open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS > <devicetree@xxxxxxxxxxxxxxx>; open list <linux-kernel@xxxxxxxxxxxxxxx> > Subject: Re: [PATCH V2 1/3] scsi: ufs: set the device reference clock > setting > > On Fri, Jun 08, 2018 at 04:36:28PM +0530, Sayali Lokhande wrote: >> From: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx> >> >> 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@xxxxxxxxxxxxxx> >> Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx> >> Signed-off-by: Sayali Lokhande <sayalil@xxxxxxxxxxxxxx> >> --- >> .../devicetree/bindings/ufs/ufshcd-pltfrm.txt | 7 +++ >> drivers/scsi/ufs/ufs.h | 9 ++++ >> drivers/scsi/ufs/ufshcd-pltfrm.c | 24 ++++++++++ >> drivers/scsi/ufs/ufshcd.c | 52 > ++++++++++++++++++++++ >> drivers/scsi/ufs/ufshcd.h | 1 + >> 5 files changed, 93 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt >> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt >> index c39dfef..4522434 100644 >> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt >> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt >> @@ -41,6 +41,12 @@ Optional properties: >> -lanes-per-direction : number of lanes available per direction - either 1 > or 2. >> Note that it is assume same number of lanes is > used both >> directions at once. If not specified, default is 2 > lanes per direction. >> +- dev-ref-clk-freq : Specify the device reference clock frequency, must > be one of the following: >> + 0: 19.2 MHz >> + 1: 26 MHz >> + 2: 38.4 MHz >> + 3: 52 MHz >> + Defaults to 26 MHz if not specified. > > I must have misunderstood your last response. I thought you could handle > things without DT. If not, my question remains. > [Sayali]: Ref clk frequency setting could vary from > platfrom-to-platform(vendor specific). Hence we need to pass it via DT. > Currently in DT we do not set/mention any ref clk frequency > parameter. Hence I have added one new DT entry to configure > required ref clk freq. The clocks property contains "ref_clk". Is that not the same clock? Why can't you read what that frequency is? Or you need to be able to change it to a specific frequency? These all look like typical oscillator frequencies, so I wouldn't expect you could change them (other than divide by 2 maybe). Rob
