On Fri, Feb 1, 2019 at 8:01 PM Maxime Ripard <maxime.ripard@xxxxxxxxxxx> wrote: > > On Tue, Jan 29, 2019 at 11:01:31PM +0530, Jagan Teki wrote: > > On Tue, Jan 29, 2019 at 8:43 PM Maxime Ripard <maxime.ripard@xxxxxxxxxxx> wrote: > > > > > > On Mon, Jan 28, 2019 at 03:06:10PM +0530, Jagan Teki wrote: > > > > On Sat, Jan 26, 2019 at 2:54 AM Maxime Ripard <maxime.ripard@xxxxxxxxxxx> wrote: > > > > > > > > > > On Fri, Jan 25, 2019 at 01:28:49AM +0530, Jagan Teki wrote: > > > > > > Minimum PLL used for MIPI is 500MHz, as per manual, but > > > > > > lowering the min rate by 300MHz can result proper working > > > > > > nkms divider with the help of desired dclock rate from > > > > > > panel driver. > > > > > > > > > > > > Signed-off-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx> > > > > > > Acked-by: Stephen Boyd <sboyd@xxxxxxxxxx> > > > > > > > > > > Going 200MHz below the minimum doesn't seem really reasonable. What > > > > > is the issue that you are trying to fix here? > > > > > > > > > > It looks like it's picking bad dividers, but if that's the case, this > > > > > isn't the proper fix. > > > > > > > > As I stated in earlier patches, the whole idea is pick the desired > > > > dclk divider based dclk rate. So the dotclock, sun4i_dclk_round_rate > > > > is unable to get the proper dclk divider at the end, so it eventually > > > > picking up wrong divider value and fired vblank timeout. > > > > > > > > So, we come-up with optimal and working min_rate 300MHz in pll-mipi to > > > > get the desired clock something like below. > > > > [ 2.415773] [drm] No driver support for vblank timestamp query. > > > > [ 2.424116] sun4i_dclk_round_rate: min_div = 4 max_div = 127, rate = 55000000 > > > > [ 2.424172] ideal = 220000000, rounded = 0 > > > > [ 2.424176] ideal = 275000000, rounded = 0 > > > > [ 2.424194] ccu_nkm_round_rate: rate = 330000000 > > > > [ 2.424197] ideal = 330000000, rounded = 330000000 > > > > [ 2.424201] sun4i_dclk_round_rate: div = 6 rate = 55000000 > > > > [ 2.424205] sun4i_dclk_round_rate: min_div = 4 max_div = 127, rate = 55000000 > > > > [ 2.424209] ideal = 220000000, rounded = 0 > > > > [ 2.424213] ideal = 275000000, rounded = 0 > > > > [ 2.424230] ccu_nkm_round_rate: rate = 330000000 > > > > [ 2.424233] ideal = 330000000, rounded = 330000000 > > > > [ 2.424236] sun4i_dclk_round_rate: div = 6 rate = 55000000 > > > > [ 2.424253] ccu_nkm_round_rate: rate = 330000000 > > > > [ 2.424270] ccu_nkm_round_rate: rate = 330000000 > > > > [ 2.424278] sun4i_dclk_recalc_rate: val = 1, rate = 330000000 > > > > [ 2.424281] sun4i_dclk_recalc_rate: val = 1, rate = 330000000 > > > > [ 2.424306] ccu_nkm_set_rate: rate = 330000000, parent_rate = 297000000 > > > > [ 2.424309] ccu_nkm_set_rate: _nkm.n = 5 > > > > [ 2.424311] ccu_nkm_set_rate: _nkm.k = 2 > > > > [ 2.424313] ccu_nkm_set_rate: _nkm.m = 9 > > > > [ 2.424661] sun4i_dclk_set_rate div 6 > > > > [ 2.424668] sun4i_dclk_recalc_rate: val = 6, rate = 55000000 > > > > > > > > But look like this wouldn't valid for all other dclock rates, say BPI > > > > panel has 30MHz clock that would failed with this logic. > > > > > > > > On the other side Allwinner BSP calculating dclk divider based on the > > > > SoC's. for A33 [1] it is fixed dclk divider of 4 and for A64 is is > > > > calculated based on the bpp/lanes. > > > > > > It looks like the A64 has the same divider of 4: > > > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c#L12 > > > > > > I think you're confusing it with the ratio between the pixel clock and > > > the dotclock, called dsi_div: > > > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/disp_al.c#L198 > > > > Ahh.. I thought this initially but as far as DSI clock computation is > > concern, the L12 tcon_div is local variable which is used for edge0 > > computation in burst mode and not for the dsi clock computation. Since > > the BSP is unable to get the tcon_div during edge0 computation, they > > defined it locally I think. > > > > You can see the lcd_clk_config() code [2], where we can see DSI clock > > computation using dsi_div value. > > > > Here is dump after the in Line 792 which is after computation[3] > > [ 10.800737] lcd_clk_config: dsi_div = 6, tcon_div = 4, lcd_div = 1 > > [ 10.800743] lcd_clk_config: lcd_dclk_freq = 55, dclk_rate = 55000000 > > [ 10.800749] lcd_clk_config: lcd_rate = 330000000, pll_rate = 330000000 > > > > The above dump the lcd_rate 330MHz is computed with panel clock, 55MHz > > into dsi_div 6. So this can be our actual divider values dclk_min_div, > > dclk_max_div in sun4i_dclk_round_rate (from > > drivers/gpu/drm/sun4i/sun4i_dotclock.c) > > I wish it was in your commit log in the first place, instead of having > to exchange multiple mails over this. > > However, I don't think that's quite true, and it might be a bug in > Allwinner's implementation (or rather something quite confusing). > > You're right that the lcd_rate and pll_rate seem to be generated from > the pixel clock, and it indeed looks like the ratio between the pixel > clock and the TCON dotclock is defined through the number of bits per > lanes. > > However, in this case, dsi_rate is actually the same than lcd_rate, > since pll_rate is going to be divided by dsi_div: > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c#L791 > > Since lcd_div is 1, it also means that in this case, dsi_rate == > dclk_rate. > > The DSI module clock however, is always set to 148.5 MHz. Indeed, if > we look at: > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c#L804 > > We can see that the rate in clk_info is used if it's different than > 0. This is filled by disp_al_lcd_get_clk_info, which, in the case of a > DSI panel, will hardcode it to 148.5 MHz: > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/disp_al.c#L164 > > So, the DSI clock is set to this here: > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c#L805 > > The TCON *module* clock (the one in the clock controller) has been set > to lcd_rate (so the pixel clock times the number of bits per lane) here: > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c#L800 > > And the PLL has been set to the same rate here: > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c#L794 Let me explain, something more. According to bsp there are clk_info.tcon_div which I will explain below. clk_info.dsi_div which is dynamic and it depends on bpp/lanes, so it is 6 for 24bpp and 4 lanes devices. PLL rate here depends on dsi_div (not tcon_div) Code here https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c#L784 is computing the actual set rate, which depends on dsi_rate. lcd_rate = dclk_rate * clk_info.dsi_div; dsi_rate = pll_rate / clk_info.dsi_div; Say if the dclk_rate 148MHz then the dsi_rate is 888MHz which set rate for above link you mentioned. Here are the evidence with some prints. https://gist.github.com/openedev/9bae2d87d2fcc06b999fe48c998b7043 https://gist.github.com/openedev/700de2e3701b2bf3ad1aa0f0fa862c9a > > Let's take a step back now: that function we were looking at, > lcd_clk_config, is called by lcd_clk_enable, which is in turn called > by disp_lcd_enable here: > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c#L1328 > > The next function being called is disp_al_lcd_cfg, and that function > will hardcode the TCON dotclock divider to 4, here: > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/disp_al.c#L240 tcon_div from BSP point-of-view of there are two variants 00) clk_info.tcon_div which is 4 and same is set the divider position in SUN4I_TCON0_DCLK_REG (like above link refer) 01) tcon_div which is 4 and used for edge timings computation https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c#L12 The real reason for 01) is again 4 is they set the divider to 4 in 00) which is technically wrong because the dividers which used during dotclock in above (dsi_div) should be used here as well. Since there is no dynamic way of doing this BSP hard-coding these values. Patches 5,6,7 on this series doing this https://patchwork.freedesktop.org/series/60847/ Hope this explanation helps?
