RE: The possible regression in kernel 4.8 - clk: imx: correct AV PLL rate formula

[Ken.Lin]

Hi Fabio,


> -----Original Message-----
> From: Fabio Estevam [mailto:festevam@xxxxxxxxx]
> Sent: Thursday, October 6, 2016 4:38 PM
> To: Ken.Lin
> Cc: shawnguo@xxxxxxxxxx; kernel@xxxxxxxxxxxxxx; sboyd@xxxxxxxxxxxxxx;
> mturquette@xxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> clk@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Peter.Stretz; Peter.Chiang;
> Akshay Bhat; Jason Moss; emil@xxxxxxxxxxxxxx
> Subject: Re: The possible regression in kernel 4.8 - clk: imx: correct AV PLL rate
> formula
> 
> Hi Ken,
> 
> On Thu, Oct 6, 2016 at 8:26 PM, Ken.Lin <ken.lin@xxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > We found a possible regression issue (not seen in kernel 4.7-stable), which has
> to do with the new NXP commit ba7f4f557eb67ee21c979c8539dc1886f5d5341c
> when we did a DP test (1920x1080@60) with clock source PLL5.
> > The DP desired pixel clock (148.5MHz that is calculated from the input of PLL
> output frequency) would be correct again when we reverted this commit.
> > Could you please help check if the commit has the side effect since it would
> have impacts on our on-going project when it requires moving from kernel 4.7
> to kernel 4.8 or newer version?
> >
> > Please check the following URL for the details
> > https://www.dropbox.com/s/7wc5jdp8unlsiob/possible_regression_for_clk_
> > imx_correct_VL_PLL_rate_formula.pdf?dl=0
> 
> Do these patches from Emil fix the issue?
> 
> http://www.spinics.net/lists/arm-kernel/msg535204.html
> 
> and
> 
> http://www.spinics.net/lists/arm-kernel/msg535203.html
> 
> Thanks


With the patches applied, the pixel clock (148500000 required for 1920x1080@60) is correct as we checked in kernel 4.7 and the actual measurement result looked good as we expected.
I think the patches should fix the issue.

Ref: /sys/kernel/debug/clk/clk_summary 

    pll5                                  1            1  1039500000          0 0
       pll5_bypass                        1            1  1039500000          0 0
          pll5_video                      1            1  1039500000          0 0
             pll5_post_div                1            1   519750000          0 0
                pll5_video_div            2            2   519750000          0 0
                   ipu2_di1_pre_sel           0            0   519750000          0 0
                      ipu2_di1_pre           0            0   173250000          0 0
                         ipu2_di1_sel           0            0   173250000          0 0
                            ipu2_di1           0            0   173250000          0 0
                   ipu2_di0_pre_sel           0            0   519750000          0 0
                      ipu2_di0_pre           0            0   173250000          0 0
                   ldb_di1_sel            1            1   519750000          0 0
                      ldb_di1_div_3_5           1            1   148500000          0 0
                         ldb_di1_podf           1            1   148500000          0 0
                            ldb_di1           2            2   148500000          0 0
                               ipu2_di0_sel           1            1   148500000          0 0
                                  ipu2_di0           1            1   148500000          0 0
                   ldb_di0_sel            1            1   519750000          0 0
                      ldb_di0_div_3_5           1            1   148500000          0 0
                         ldb_di0_podf           1            1   148500000          0 0
                            ldb_di0           1            1   148500000          0 0


Ref: kernel debug messages

[  113.848959] imx-ipuv3-crtc imx-ipuv3-crtc.6: ipu_crtc_mode_set_nofb: mode->hdisplay: 1920
[  113.857201] imx-ipuv3-crtc imx-ipuv3-crtc.6: ipu_crtc_mode_set_nofb: mode->vdisplay: 1080
[  113.865421] imx-ipuv3-crtc imx-ipuv3-crtc.6: ipu_crtc_mode_set_nofb: attached to encoder types 0x8
[  113.874483] imx-ipuv3 2800000.ipu: disp 0: panel size = 1920 x 1080
[  113.880803] imx-ipuv3 2800000.ipu: Clocks: IPU 264000000Hz DI 75833334Hz Needed 148500000Hz
[  113.889252] imx-ipuv3 2800000.ipu: Want 148500000Hz IPU 264000000Hz DI 75833334Hz using DI, 75833334Hz
[  113.898768] imx-ldb 2000000.aips-bus:ldb@020e0008: imx_ldb_set_clock: now: 227500000 want: 519750000
[  113.908018] imx-ldb 2000000.aips-bus:ldb@020e0008: imx_ldb_set_clock after: 519750000
[  113.915886] imx-ldb 2000000.aips-bus:ldb@020e0008: imx_ldb_set_clock: now: 148500000 want: 148500000
[  113.925050] imx-ldb 2000000.aips-bus:ldb@020e0008: imx_ldb_set_clock after: 148500000
[  113.932928] imx-ldb 2000000.aips-bus:ldb@020e0008: imx_ldb_set_clock: now: 519750000 want: 519750000
[  113.942096] imx-ldb 2000000.aips-bus:ldb@020e0008: imx_ldb_set_clock after: 519750000
[  113.949938] imx-ldb 2000000.aips-bus:ldb@020e0008: imx_ldb_set_clock: now: 148500000 want: 148500000
[  113.959104] imx-ldb 2000000.aips-bus:ldb@020e0008: imx_ldb_set_clock after: 148500000

> 
> --
> This message has been scanned for viruses and dangerous content by
> MailScanner, and is believed to be clean.

Thank you


-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.