From mboxrd@z Thu Jan 1 00:00:00 1970 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 Message-ID: <002401d4093d$256fdc90$704f95b0$@codeaurora.org> References: <1528455990-24572-1-git-send-email-sayalil@codeaurora.org> <1528455990-24572-2-git-send-email-sayalil@codeaurora.org> <20180612192636.GA31725@rob-hp-laptop> <000101d403d3$87210d20$95632760$@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Language: en-us Sender: linux-kernel-owner@vger.kernel.org To: 'Rob Herring' Cc: 'Subhash Jadavani' , 'Can Guo' , 'Vivek Gautam' , 'Rajendra Nayak' , 'Vinayak Holikatti' , "'James E.J. Bottomley'" , "'Martin K. Petersen'" , asutoshd@codeaurora.org, 'Evan Green' , linux-scsi@vger.kernel.org, 'Mark Rutland' , 'Mathieu Malaterre' , "'open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS'" , 'open list' List-Id: devicetree@vger.kernel.org Hi Rob, Please check my comment inline. Thanks, Sayali -----Original Message----- From: Rob Herring [mailto:robh@kernel.org]=20 Sent: Thursday, June 14, 2018 7:59 PM To: sayali Cc: Subhash Jadavani ; Can Guo = ; Vivek Gautam ; = Rajendra Nayak ; Vinayak Holikatti = ; James E.J. Bottomley = ; Martin K. Petersen = ; asutoshd@codeaurora.org; Evan Green = ; linux-scsi@vger.kernel.org; Mark Rutland = ; Mathieu Malaterre ; open = list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS = ; open list Subject: Re: [PATCH V2 1/3] scsi: ufs: set the device reference clock = setting On Thu, Jun 14, 2018 at 5:33 AM, sayali 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 > Cc: subhashj@codeaurora.org; cang@codeaurora.org;=20 > vivek.gautam@codeaurora.org; rnayak@codeaurora.org;=20 > vinholikatti@gmail.com; jejb@linux.vnet.ibm.com;=20 > martin.petersen@oracle.com; asutoshd@codeaurora.org;=20 > evgreen@chromium.org; linux-scsi@vger.kernel.org; Mark Rutland=20 > ; Mathieu Malaterre ; open=20 > list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS=20 > ; open list > Subject: Re: [PATCH V2 1/3] scsi: ufs: set the device reference clock=20 > setting > > On Fri, Jun 08, 2018 at 04:36:28PM +0530, Sayali Lokhande wrote: >> From: Subhash Jadavani >> >> UFS host supplies the reference clock to UFS device and UFS device=20 >> specification allows host to provide one of the 4 frequencies (19.2=20 >> MHz, >> 26 MHz, 38.4 MHz, 52 MHz) for reference clock. Host should set the=20 >> device reference clock frequency setting in the device based on what=20 >> frequency it is supplying to UFS device. >> >> Signed-off-by: Subhash Jadavani >> Signed-off-by: Can Guo >> Signed-off-by: Sayali Lokhande >> --- >> .../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 -=20 >> either 1 > or 2. >> Note that it is assume same number of lanes=20 >> 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=20 > handle things without DT. If not, my question remains. > [Sayali]: Ref clk frequency setting could vary from=20 > 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=20 > 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