Hi Rob, Please check my comment inline. Thanks, Sayali -----Original Message----- From: Rob Herring [mailto:robh@xxxxxxxxxx] Sent: Thursday, June 14, 2018 7:59 PM To: sayali <sayalil@xxxxxxxxxxxxxx> Cc: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>; Can Guo <cang@xxxxxxxxxxxxxx>; Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>; Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>; Vinayak Holikatti <vinholikatti@xxxxxxxxx>; James E.J. Bottomley <jejb@xxxxxxxxxxxxxxxxxx>; Martin K. Petersen <martin.petersen@xxxxxxxxxx>; asutoshd@xxxxxxxxxxxxxx; Evan Green <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 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). [Sayali] : It is the same "ref_clk", but we need to be able to change it to a specific frequency as per requirement. Thus, we need new DT entry to specify/override reference clock frequency as per need. Rob
