From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sayali Lokhande Subject: Re: [PATCH V2 1/3] scsi: ufs: set the device reference clock setting Date: Wed, 4 Jul 2018 19:06:15 +0530 Message-ID: <4d8c8171-2ead-8953-afce-a30f260cf9c9@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> <002401d4093d$256fdc90$704f95b0$@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 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 , devicetree@vger.kernel.org, "linux-kernel@vger.kernel.org" List-Id: devicetree@vger.kernel.org On 7/3/2018 11:34 PM, Rob Herring wrote: > On Thu, Jun 21, 2018 at 2:52 AM sayali wrote: >> Hi Rob, >> >> Please check my comment inline. > As mentioned in the back and forth comments previously in this thread, > please fix your email client (hint: you can't use Outlook) and > properly quote your replies (i.e. the leading ">") I have started using Thunderbird now. Hope you can see my replies correctly this time. > >> Thanks, >> Sayali >> -----Original Message----- >> From: Rob Herring [mailto:robh@kernel.org] >> 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; >>> 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 >>> ; 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 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 >>>> 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 >>>> 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 - >>>> 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. > That is not what your patch does. It just tells the device what the > frequency is. If you need to get the rate, use "clk_get_rate" on > "ref_clk". If you need to actually set it to a specific frequency, > then we have properties for that already (assigned-clock-rates). Yes, we need to set it to a specific frequency. I will use "assigned-clock-rates" for passing ref_clk frequency in next patch set. > > Seems to me that by the time you get to Linux, the bootloader would > have already set this. Otherwise, how do you boot? Seems like you > would want to read the attr and ensure "ref_clk" freq matches. Yes, ref_clk freq will be already set in device via bootloader. In Kernel, before updating ref_clk freq (if required and passed via DT), we are reading the current ref_clk set in device and only if it is different than what has been passed via DT, we will be updating ref_clk freq, otherwise we just return. > Rob Thanks, Sayali