On Tue, Apr 18, 2023 at 6:53 AM Adam Ford <aford173@xxxxxxxxx> wrote: > > On Mon, Apr 17, 2023 at 2:00 AM Alexander Stein > <alexander.stein@xxxxxxxxxxxxxxx> wrote: > > > > Hi, > > > > Am Montag, 17. April 2023, 00:31:24 CEST schrieb Adam Ford: > > > On Sun, Apr 16, 2023 at 5:07 PM Marek Vasut <marex@xxxxxxx> wrote: > > > > On 4/15/23 12:40, Adam Ford wrote: > > > > > According to Table 13-45 of the i.MX8M Mini Reference Manual, the min > > > > > and max values for M and the frequency range for the VCO_out > > > > > calculator were incorrect. This also appears to be the case for the > > > > > imx8mn and imx8mp. > > > > > > > > > > To fix this, make new variables to hold the min and max values of m > > > > > and the minimum value of VCO_out, and update the PMS calculator to > > > > > use these new variables instead of using hard-coded values to keep > > > > > the backwards compatibility with other parts using this driver. > > > > > > > > [...] > > > > > > > > > static const struct samsung_dsim_driver_data imx8mm_dsi_driver_data = > > > > > { > > > > > > > > > > @@ -470,6 +485,9 @@ static const struct samsung_dsim_driver_data > > > > > imx8mm_dsi_driver_data = {> > > > > > > */ > > > > > > > > > > .pll_p_offset = 14, > > > > > .reg_values = imx8mm_dsim_reg_values, > > > > > > > > > > + .m_min = 64, > > > > > + .m_max = 1023, > > > > > + .vco_min = 1050, > > > > > > > > You might want to call this 'min_freq' since there is a 'max_freq' which > > > > seems to indicate what VCO max frequency is. > > > > > > > > Note that the same datasheet contains the following information: > > > > " > > > > MIPI_DPHY_M_PLLPMS field descriptions > > > > > > > > 12–4 PMS_M > > > > Specifies the PLL PMS value for the M divider > > > > NOTE: The programmable divider range should be within 25 to 125 to > > > > ensure PLL stability. > > > > > > I was confused by this because this statement is not consistent with > > > the link they reference jumps me to the table where it reads M is > > > between 64 and 1023. > > > > > > > NOTE: The M and P divider values should be considered together to ensure > > > > VCO ouput frequency > > > > (VCO_out) range is between 350 MHz to 750 MHz. > > > > Please refer to the topic DPHY PLL for more information. > > > > > > I was confused by this too, because the NXP documentation reads the > > > 350 - 750MHz that you state, but "Table 13-45: DPHY PLL Parameters" > > > which immediately follows that sentence on page 4158 shows VCO_out is > > > between 1050-2100 MHz. I reached out to my NXP rep asking if the VCO_out is 350-750 or if it should be 1050-2100, and received the following statement: " Yes it is definitely wrong, the one that is part of the NOTE in MIPI_DPHY_M_PLLPMS register table against PMS_P, PMS_M and PMS_S is not correct. I will report this to Doc team, the one customer should be take into account is the Table 13-40 DPHY PLL Parameters and the Note above." Table 13-40 (for the Nano) reads the VCO_out is 1050-2100, despite other text stating 350-750MHz, so I believe this patch is appropriate. I'll add the above statement to the commit message as confirmation when I submit a V2 of this series. adam > > > > > > I compared the PMS values for a variety of frequencies to those that > > > were set in the downstream NXP code, and the PMS values matched. > > > Maybe someone from NXP can explain the discrepancy. > > > > Also note that, according to Table 13-28 in RM (Rev 2 07/2022) for i.MX8M > > Nano, VCO_out and Fout has a maximum of 1500MHz only. Although the note above > > mentions a range of 1050-2100MHz... > > I looked up the limits in NXP's downstream kernel [1] , and I believe > these values match the table in the reference manual instead of the > conflicting sentence. I am guessing this is why the PMS values I get > match those of the NXP downstream kernel. > > adam > > [1] - https://github.com/nxp-imx/linux-imx/blob/lf-6.1.y/drivers/gpu/drm/imx/sec_mipi_pll_1432x.h#L38 > > > > > Best regards, > > Alexander > > -- > > TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany > > Amtsgericht München, HRB 105018 > > Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider > > http://www.tq-group.com/ > > > >