Message-ID: <CAOf5uw=3fiMuhcj3kDtCaGNTsxHKRrYb79MXZ+yUZtmf0jU10A@mail.gmail.com>
Date:   Thu, 11 Jul 2019 19:43:16 +0200
From:   Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Jagan Teki <jagan@...rulasolutions.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Chen-Yu Tsai <wens@...e.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-amarula <linux-amarula@...rulasolutions.com>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH v6 11/22] clk: sunxi-ng: a64: Add minimum rate for PLL_MIPI

Hi Maxime

On Thu, Jul 11, 2019 at 2:23 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
>
> On Fri, Jul 05, 2019 at 07:52:27PM +0200, Michael Nazzareno Trimarchi wrote:
> > On Wed, Jul 3, 2019 at 1:49 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> > >
> > > On Tue, Jun 25, 2019 at 09:00:36PM +0530, Jagan Teki wrote:
> > > > On Tue, Jun 25, 2019 at 8:19 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> > > > >
> > > > > On Thu, Jun 20, 2019 at 11:57:44PM +0530, Jagan Teki wrote:
> > > > > > On Fri, Jun 14, 2019 at 7:54 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> > > > > > >
> > > > > > > On Wed, Jun 05, 2019 at 01:03:16PM +0530, Jagan Teki wrote:
> > > > > > > > On Wed, Jun 5, 2019 at 12:19 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> > > > > > > > >
> > > > > > > > > Hi,
> > > > > > > > >
> > > > > > > > > I've reordered the mail a bit to work on chunks
> > > > > > > > >
> > > > > > > > > On Fri, May 24, 2019 at 03:37:42PM +0530, Jagan Teki wrote:
> > > > > > > > > > > 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
> > > > > > > > > >
> > > > > > > > > > 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
> > > > > > > > >
> > > > > > > > > Ok, so we agree up to this point, and the prints confirm that the
> > > > > > > > > analysis above is the right one.
> > > > > > > > >
> > > > > > > > > > > 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
> > > > > > > > >
> > > > > > > > > Your patch doesn't address that, so let's leave that one alone.
> > > > > > > >
> > > > > > > > Basically this is final pll set rate when sun4i_dotclock.c called the
> > > > > > > > desired rate with ccu_nkm.c so it ended the final rate with parent as
> > > > > > > > Line 8 of
> > > > > > > > https://gist.github.com/openedev/700de2e3701b2bf3ad1aa0f0fa862c9a
> > > > > > >
> > > > > > > If that's important to the driver, it should be set explicitly then,
> > > > > > > and not work by accident.
> > > > > > >
> > > > > > > > > > > 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'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?
> > > > > > > > >
> > > > > > > > > It doesn't.
> > > > > > > > >
> > > > > > > > > The clock tree is this one:
> > > > > > > > >
> > > > > > > > > PLL(s) -> TCON module clock -> TCON dotclock.
> > > > > > > > >
> > > > > > > > > The links I mentioned above show that the clock set to lcd_rate is the
> > > > > > > > > TCON module clocks (and it should be the one taking the bpp and lanes
> > > > > > > > > into account), while the TCON dotclock uses a fixed divider of 4.
> > > > > > > >
> > > > > > > > Sorry, I can argue much other-than giving some code snips, according to [1]
> > > > > > > >
> > > > > > > > 00) Line 785, 786 with dclk_rate 148000000
> > > > > > > >
> > > > > > > > lcd_rate = dclk_rate * clk_info.dsi_div;
> > > > > > > > pll_rate = lcd_rate * clk_info.lcd_div;
> > > > > > > >
> > > > > > > > Since dsi_div is 6 (bpp/lanes), lcd_div 1
> > > > > > > >
> > > > > > > > lcd_rate = 888000000, pll_rate = 888000000
> > > > > > > >
> > > > > > > > 01)  Line 801, 804 are final rates computed as per clock driver (say
> > > > > > > > ccu_nkm in mainline)
> > > > > > > >
> > > > > > > > lcd_rate_set=891000000
> > > > > > > >
> > > > > > > > As per your comments if it would be 4 then the desired numbers are
> > > > > > > > would be 592000000 not 888000000.
> > > > > > > >
> > > > > > > > This is what I'm trying to say in all mails, and same as verified with
> > > > > > > > 2-lanes devices as well where the dsi_div is 12 so the final rate is
> > > > > > > > 290MHz * 12
> > > > > > >
> > > > > > > In the code you sent, you're forcing a divider on the internal TCON
> > > > > > > clock, while that one is fixed in the BSP.
> > > > > > >
> > > > > > > There's indeed the bpp / lanes divider, but it's used in the *parent*
> > > > > > > clock of the one you're changing.
> > > > > > >
> > > > > > > And the dsi0_clk clock you pointed out in the code snippet is yet
> > > > > > > another clock, the MIPI DSI module clock.
> > > > > >
> > > > > > Correct, look like I refereed wrong reference in the above mail. sorry
> > > > > > for the noise.
> > > > > >
> > > > > > Actually I'm trying to explain about pll_rate here which indeed
> > > > > > depends on dsi.div
> > > > > > https://github.com/BPI-SINOVOIP/BPI-M64-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c#L786
> > > > > >
> > > > > > lcd_rate = dclk_rate * clk_info.dsi_div;
> > > > > > pll_rate = lcd_rate * clk_info.lcd_div;
> > > > > >
> > > > > > Say
> > > > > >
> > > > > > 1) For 148MHz dclk_rate with dsi_div is 6 (24/4) lcd_div is 1 which
> > > > > > resulting pll_rate is 888MHz.
> > > > > >
> > > > > > 2) For 30MHz dclk_rate with 4 lane and 24 RGB the resulting pll_rate is 180MHz
> > > > > >
> > > > > > 3) For 27.5MHz dclk_rate with 2 lane and 24 RGB the resulting pll_rate is 330MHz
> > > > > >
> > > > > > Here is the few more logs in code, for case 2)
> > > > > >
> > > > > > [    1.920441] sun4i_dclk_round_rate: min_div = 6 max_div = 6, rate = 30000000
> > > > > > [    1.920505] ideal = 180000000, rounded = 178200000
> > > > > > [    1.920509] sun4i_dclk_round_rate: div = 6 rate = 29700000
> > > > > > [    1.920514] sun4i_dclk_round_rate: min_div = 6 max_div = 6, rate = 30000000
> > > > > > [    1.920532] ideal = 1800ls and one DSI-RGB bridge. All of them do use
> > > > PLL_MIPI (pll_rate) and it indeed depends on bpp/lanes
> > > >00000, rounded = 178200000
> > > > > > [    1.920535] sun4i_dclk_round_rate: div = 6 rate = 29700000
> > > > > > [    1.920572] sun4i_dclk_recalc_rate: val = 1, rate = 178200000
> > > > > > [    1.920576] sun4i_dclk_recalc_rate: val = 1, rate = 178200000
> > > > > > [    1.920597] rate = 178200000
> > > > > > [    1.920599] parent_rate = 297000000
> > > > > > [    1.920602] reg = 0x90c00000
> > > > > > [    1.920605] _nkm.n = 3, nkm->n.offset = 0x1, nkm->n.shift = 8
> > > > > > [    1.920609] _nkm.k = 2, nkm->k.offset = 0x1, nkm->k.shift = 4
> > > > > > [    1.920612] _nkm.m = 10, nkm->m.offset = 0x1, nkm->m.shift = 0
> > > > > > [    1.920958] sun4i_dclk_set_rate div 6
> > > > > > [    1.920966] sun4i_dclk_recalc_rate: val = 6, rate = 29700000
> > > > > >
> > > > > > and clk_summary:
> > > > > >
> > > > > >     pll-video0                        1        1        1   297000000
> > > > > >         0     0  50000
> > > > > >        hdmi                           0        0        0   297000000
> > > > > >         0     0  50000
> > > > > >        tcon1                          0        0        0   297000000
> > > > > >         0     0  50000
> > > > > >        pll-mipi                       1        1        1   178200000
> > > > > >         0     0  50000
> > > > > >           tcon0                       2        2        1   178200000
> > > > > >         0     0  50000
> > > > > >              tcon-pixel-clock         1        1        1    29700000
> > > > > >         0     0  50000
> > > > > >        pll-video0-2x                  0        0        0   594000000
> > > > > >         0     0  50000
> > > > >
> > > > > This discussion is going nowhere. I'm telling you that your patch
> > > > > doesn't apply the divider you want on the proper clock, and you're
> > > > > replying that indeed, you're applying it on the wrong clock.
> > > > >
> > > > > It might work by accident in your case, but the board I have here
> > > > > clearly indicates otherwise, so there's two possible way out here:
> > > > >
> > > > >   - Either you apply that divider to the TCON *module* clock, and not
> > > > >     the dclk
> > > > >
> > > > >   - Or you point to somewhere in the allwinner code where the bpp /
> > > > >     lanes divider is used for the dclk divider.
> > > >
> > > > I don't know how to proceed further on this, as you say it might work
> > > > in accident but I have tested this in A33, A64 and R40 with 4
> > > > different DSI panels and one DSI-RGB bridge. All of them do use
> > > > PLL_MIPI (pll_rate) and it indeed depends on bpp/lanes
> > > >
> > > > 4-lane, 24-bit: Novatek NT35596 panel
> > > > 4-lane, 24-bit: Feiyang, FY07024di26a30d panel
> > > > 4-lane, 24-bit: Bananapi-s070wv20 panel
> > > > 2-lane, 24-bit: Techstar,ts8550b panel
> > > >
> > > > and
> > > >
> > > > 4-lane, 24-bit, ICN6211 DSI-to-RGB bridge panel
> > > >
> > > > All above listed panels and bridges are working as per BSP and do
> > > > follow bpp/lanes and for DIVIDER 4 no panel is working.
> > >
> > > Look. I'm not saying that there's no issue, I'm saying that your
> > > patch, applied to the clock you're applying it to, doesn't make sense
> > > and isn't what the BSP does.
> >
> > tcon-pixel clock is the rate that you want to achive on display side
> > and if you have 4 lanes 32bit or lanes and different bit number that
> > you need to have a clock that is able to put outside bits and speed
> > equal to pixel-clock * bits / lanes. so If you want a pixel-clock of
> > 40 mhz and you have 32bits and 4 lanes you need to have a clock of
> > 40 * 32 / 4 in no-burst mode. I think that this is done but most of
> > the display.
>
> So this is what the issue is then?
>
> This one does make sense, and you should just change the rate in the
> call to clk_set_rate in sun4i_tcon0_mode_set_cpu.
>
> I'm still wondering why that hasn't been brought up in either the
> discussion or the commit log before though.
>
Something like this?

drivers/gpu/drm/sun4i/sun4i_tcon.c     | 20 +++++++++++---------
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  2 --
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c
b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 64c43ee6bd92..42560d5c327c 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -263,10 +263,11 @@ static int sun4i_tcon_get_clk_delay(const struct
drm_display_mode *mode,
 }

 static void sun4i_tcon0_mode_set_common(struct sun4i_tcon *tcon,
-                                       const struct drm_display_mode *mode)
+                                       const struct drm_display_mode *mode,
+                                       u32 tcon_mul)
 {
        /* Configure the dot clock */
-       clk_set_rate(tcon->dclk, mode->crtc_clock * 1000);
+       clk_set_rate(tcon->dclk, mode->crtc_clock * tcon_mul * 1000);

        /* Set the resolution */
        regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
@@ -335,12 +336,13 @@ static void sun4i_tcon0_mode_set_cpu(struct
sun4i_tcon *tcon,
        u8 bpp = mipi_dsi_pixel_format_to_bpp(device->format);
        u8 lanes = device->lanes;
        u32 block_space, start_delay;
-       u32 tcon_div;
+       u32 tcon_div, tcon_mul;

-       tcon->dclk_min_div = SUN6I_DSI_TCON_DIV;
-       tcon->dclk_max_div = SUN6I_DSI_TCON_DIV;
+       tcon->dclk_min_div = 4;
+       tcon->dclk_max_div = 127;

-       sun4i_tcon0_mode_set_common(tcon, mode);
+       tcon_mul = bpp / lanes;
+       sun4i_tcon0_mode_set_common(tcon, mode, tcon_mul);

        /* Set dithering if needed */
        sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
@@ -366,7 +368,7 @@ static void sun4i_tcon0_mode_set_cpu(struct
sun4i_tcon *tcon,
         */
        regmap_read(tcon->regs, SUN4I_TCON0_DCLK_REG, &tcon_div);
        tcon_div &= GENMASK(6, 0);
-       block_space = mode->htotal * bpp / (tcon_div * lanes);
+       block_space = mode->htotal * tcon_div * tcon_mul;
        block_space -= mode->hdisplay + 40;

        regmap_write(tcon->regs, SUN4I_TCON0_CPU_TRI0_REG,
@@ -408,7 +410,7 @@ static void sun4i_tcon0_mode_set_lvds(struct
sun4i_tcon *tcon,

        tcon->dclk_min_div = 7;
        tcon->dclk_max_div = 7;
-       sun4i_tcon0_mode_set_common(tcon, mode);
+       sun4i_tcon0_mode_set_common(tcon, mode, 1);

        /* Set dithering if needed */
        sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
@@ -487,7 +489,7 @@ static void sun4i_tcon0_mode_set_rgb(struct
sun4i_tcon *tcon,

        tcon->dclk_min_div = 6;
        tcon->dclk_max_div = 127;
-       sun4i_tcon0_mode_set_common(tcon, mode);
+       sun4i_tcon0_mode_set_common(tcon, mode, 1);

        /* Set dithering if needed */
        sun4i_tcon0_mode_set_dithering(tcon, connector);
diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
index 5c3ad5be0690..a07090579f84 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
@@ -13,8 +13,6 @@
 #include <drm/drm_encoder.h>
 #include <drm/drm_mipi_dsi.h>

-#define SUN6I_DSI_TCON_DIV     4
-
 struct sun6i_dsi {
        struct drm_connector    connector;
        struct drm_encoder      encoder;


> > Now in burst mode I don't know how should work the calculation of
> > the clock for the require bandwidth and even I understand your
> > comment I would like to have your clock tree after you boot on the
> > display side and if it is possible I want to assemble a kit like you
> > have.
>
> The setup is probably going to be a bit difficult to reproduce, it's a
> prototype that I have that can't really be found anywhere. Jagan asked
> me on IRC for the reference, and he found the part, but it's unclear
> to me if it can be easily adapted to a common board.
>
> However, I'm not even sure we need this. I'll test the next version
> and let you know if it works.
>
> Maxime
>
> --
> Maxime Ripard, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com



-- 
| Michael Nazzareno Trimarchi                     Amarula Solutions BV |
| COO  -  Founder                                      Cruquiuskade 47 |
| +31(0)851119172                                 Amsterdam 1018 AM NL |
|                  [`as] http://www.amarulasolutions.com               |

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