Messages in this thread Patch in this message | | | From | "sayali" <> | Subject | RE: [PATCH V2 1/3] scsi: ufs: set the device reference clock setting | Date | Thu, 21 Jun 2018 14:22:04 +0530 |
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Hi Rob,
Please check my comment inline.
Thanks, Sayali -----Original Message----- From: Rob Herring [mailto:robh@kernel.org] Sent: Thursday, June 14, 2018 7:59 PM To: sayali <sayalil@codeaurora.org> Cc: Subhash Jadavani <subhashj@codeaurora.org>; Can Guo <cang@codeaurora.org>; Vivek Gautam <vivek.gautam@codeaurora.org>; Rajendra Nayak <rnayak@codeaurora.org>; Vinayak Holikatti <vinholikatti@gmail.com>; James E.J. Bottomley <jejb@linux.vnet.ibm.com>; Martin K. Petersen <martin.petersen@oracle.com>; asutoshd@codeaurora.org; Evan Green <evgreen@chromium.org>; linux-scsi@vger.kernel.org; Mark Rutland <mark.rutland@arm.com>; Mathieu Malaterre <malat@debian.org>; open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS <devicetree@vger.kernel.org>; open list <linux-kernel@vger.kernel.org> 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@codeaurora.org> wrote: > Comment inline. > > Thanks, > Sayali > -----Original Message----- > From: Rob Herring [mailto:robh@kernel.org] > Sent: Wednesday, June 13, 2018 12:57 AM > To: Sayali Lokhande <sayalil@codeaurora.org> > Cc: subhashj@codeaurora.org; cang@codeaurora.org; > vivek.gautam@codeaurora.org; rnayak@codeaurora.org; > vinholikatti@gmail.com; jejb@linux.vnet.ibm.com; > martin.petersen@oracle.com; asutoshd@codeaurora.org; > evgreen@chromium.org; linux-scsi@vger.kernel.org; Mark Rutland > <mark.rutland@arm.com>; Mathieu Malaterre <malat@debian.org>; open > list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS > <devicetree@vger.kernel.org>; open list <linux-kernel@vger.kernel.org> > 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@codeaurora.org> >> >> 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> >> --- >> .../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
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