Re: [PATCH v5 5/8] clk: stm32: Fix stm32f429's ltdc driver hang in set clock rate, fix duplicated ltdc clock register to 'clk_core' case ltdc's clock turn off by clk_disable_unused()

[dillon min <dillon.minfei@xxxxxxxxx>]

Hi Stephen,

Thanks for reviewing.

On Wed, May 27, 2020 at 9:44 AM Stephen Boyd <sboyd@xxxxxxxxxx> wrote:
>
> Quoting dillon.minfei@xxxxxxxxx (2020-05-24 20:45:45)
> > From: dillon min <dillon.minfei@xxxxxxxxx>
> >
> > ltdc set clock rate crashed
> >    'post_div_data[]''s pll_num is PLL_I2S, PLL_SAI (number is 1,2). but,
>
> Please write "post_div_data[]'s" if it is possessive. "But" doesn't
> start a sentence. This is one sentence, not two.
Ok.

>
> >     as pll_num is offset of 'clks[]' input to clk_register_pll_div(), which
> >     is FCLK, CLK_LSI, defined in 'include/dt-bindings/clock/stm32fx-clock.h'
> >     so, this is a null object at the register time.
> >     then, in ltdc's clock is_enabled(), enable(), will call to_clk_gate().
> >     will return a null object, cause kernel crashed.
> >     need change pll_num to PLL_VCO_I2S, PLL_VCO_SAI for 'post_div_data[]'
> >
> >  duplicated ltdc clock
> >    'stm32f429_gates[]' has a member 'ltdc' register to 'clk_core', but no
> >     upper driver use it, ltdc driver use the lcd-tft defined in
> >    'stm32f429_aux_clk[]'. after system startup, as stm32f429_gates[]'s ltdc
> >     enable_count is zero, so turn off by clk_disable_unused()
>
> I sort of follow this. Is this another patch? Seems like two things are
> going on here.

This patch fix two bugs about stm32's clock.
bug1:  ltdc driver loading hang in clk_set_rate(), this is due to
misuse ‘PLL_VCO_SAI' and
           'PLL_SAI'.

 speak in short, from the below code,
    ’PLL_SAI' is 2, 'PLL_VCO_SAI' is 7.
    'post_div' point to 'post_div_data[]', 'post_div->pll_num' is
PLL_I2S, PLL_SAI.
    'clks[PLL_VCOM_SAI' has vaild 'struct clk_hw* ' return from
stm32f4_rcc_register_pll()
    but, at line 1776, use the 'clks[post_div->pll_num]', equal to
'clks[PLL_SAI]', this is invaild
    at that time.

include/dt-bindings/clock/stm32fx-clock.h
29 #define PLL_VCO_SAI             7

drivers/clk/clk-stm32f4.c
 494 enum {
 495         PLL,
 496         PLL_I2S,
 497         PLL_SAI,
 498 };


 558 static const struct stm32f4_pll_post_div_data
post_div_data[MAX_POST_DIV] = {
 559         { CLK_I2SQ_PDIV, PLL_I2S, "plli2s-q-div", "plli2s-q",
 560                 CLK_SET_RATE_PARENT, STM32F4_RCC_DCKCFGR, 0, 5, 0, NULL},
 561
 562         { CLK_SAIQ_PDIV, PLL_SAI, "pllsai-q-div", "pllsai-q",
 563                 CLK_SET_RATE_PARENT, STM32F4_RCC_DCKCFGR, 8, 5, 0, NULL },
 564
 565         { NO_IDX, PLL_SAI, "pllsai-r-div", "pllsai-r", CLK_SET_RATE_PARENT,
 566                 STM32F4_RCC_DCKCFGR, 16, 2, 0, post_divr_table },
 567 };


1759         clks[PLL_VCO_SAI] = stm32f4_rcc_register_pll("vco_in",
1760                         &data->pll_data[2], &stm32f4_clk_lock);
1761
1762         for (n = 0; n < MAX_POST_DIV; n++) {
1763                 const struct stm32f4_pll_post_div_data *post_div;
1764                 struct clk_hw *hw;
1765
1766                 post_div = &post_div_data[n];
1767
1768                 hw = clk_register_pll_div(post_div->name,
1769                                 post_div->parent,
1770                                 post_div->flag,
1771                                 base + post_div->offset,
1772                                 post_div->shift,
1773                                 post_div->width,
1774                                 post_div->flag_div,
1775                                 post_div->div_table,
1776                                 clks[post_div->pll_num],
1777                                 &stm32f4_clk_lock);
1778
1779                 if (post_div->idx != NO_IDX)
1780                         clks[post_div->idx] = hw;
1781         }

bug2: ltdc's clock turn off by clk_disable_unused()

from your comments at '[PATCH v3 4/5] clk: stm32: Fix stm32f429 ltdc
driver loading hang
 in clk set rate. keep ltdc clk running after kernel startup' , i go
deep into the code, found
stm32's clk driver register two gate clk to clk core by
clk_hw_register_gate() and
clk_hw_register_composite()

first: 'stm32f429_gates[]', clk name is 'ltdc', this is no user used.
second: 'stm32f429_aux_clk[]', clk name is 'lcd-tft', this is used by
ltdc driver

both of them point to the same offset of stm32's RCC register. after
kernel enter console,
clk core turn off ltdc's clk as 'stm32f429_gates[]' is unused. but,
actually 'stm32f429_aux_clk[]'
is in use.

i can separate this patch to two, each bug a patch if necessary

>
> >
> > Changes since V3:
> > 1 drop last wrong changes about 'CLK_IGNORE_UNUSED' patch
> > 2 fix PLL_SAI mismatch with PLL_VCO_SAI
>
> This change log goes under the --- below.
ok

>
> >
> > Signed-off-by: dillon min <dillon.minfei@xxxxxxxxx>
>
> Any Fixes tag?
ok, will add --fixup in git commit next time, this patch fix two bugs,
i should make two commit, each one has a
fixes tag, right?
first point to '517633e clk: stm32f4: Add post divisor for I2S & SAI PLLs'
second point to 'daf2d11 clk: stm32f4: Add lcd-tft clock'