Re: [PATCH 1/3] drm: rockchip: hdmi: remove vop_crtc_mode_fixup to fix clock handling【请注意，邮件由linux-rockchip-bounces+andy.yan=rock-chips.com at lists.infradead.org代发】

[crj]

Hi, Douglas

在 2020/9/22 17:31, Vicente Bergas 写道:
> On Tue, Sep 22, 2020 at 11:24 AM crj <algea.cao at rock-chips.com> wrote:
>> Hello Vicente,
>>
>> 在 2020/9/22 15:40, Andy Yan 写道:
>>> Add our HDMI driver owner Algea to list.
>>>
>>> On 9/22/20 2:18 AM, Vicente Bergas wrote:
>>>> Under certain conditions vop_crtc_mode_fixup rounds the clock
>>
>> May I ask under what conditions that the clock of HDMI will
>>
>> be changed to 148501000?  In general, the description of clock
>>
>> in EDID will not be detailed below the thousands place.
> There is no clock in the EDID with 1KHz resolution, the clock is
> 148500000 which has 500KHz resolution.
> It is the function vop_crtc_mode_fixup that gets xxx0000 and returns xxx1000

I checked the commit msg of commit 287422a95fe2 ("drm/rockchip: Round up 
_before_ giving to the clock framework").

Round up hdmi clock is for some panels with special clocks.  Are these 
panels clock can't be divided correctly common?

>>>> 148500000 to 148501000 which leads to the following error:
>>>> dwhdmi-rockchip ff940000.hdmi: PHY configuration failed (clock
>>>> 148501000)
>>>>
>>>> The issue was found on RK3399 booting with u-boot. U-boot configures the
>>>> display at 2560x1440 and then linux comes up with a black screen.
>>>> A workaround was to un-plug and re-plug the HDMI display.
>>>>
>>>> Signed-off-by: Vicente Bergas <vicencb at gmail.com>
>>>> Tested-by: Vicente Bergas <vicencb at gmail.com>
>>>> ---
>>>>    drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 45 ---------------------
>>>>    1 file changed, 45 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>> b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>> index c80f7d9fd13f..fe80da652994 100644
>>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>> @@ -1142,50 +1142,6 @@ static void vop_crtc_disable_vblank(struct
>>>> drm_crtc *crtc)
>>>>        spin_unlock_irqrestore(&vop->irq_lock, flags);
>>>>    }
>>>>    -static bool vop_crtc_mode_fixup(struct drm_crtc *crtc,
>>>> -                const struct drm_display_mode *mode,
>>>> -                struct drm_display_mode *adjusted_mode)
>>>> -{
>>>> -    struct vop *vop = to_vop(crtc);
>>>> -    unsigned long rate;
>>>> -
>>>> -    /*
>>>> -     * Clock craziness.
>>>> -     *
>>>> -     * Key points:
>>>> -     *
>>>> -     * - DRM works in in kHz.
>>>> -     * - Clock framework works in Hz.
>>>> -     * - Rockchip's clock driver picks the clock rate that is the
>>>> -     *   same _OR LOWER_ than the one requested.
>>>> -     *
>>>> -     * Action plan:
>>>> -     *
>>>> -     * 1. When DRM gives us a mode, we should add 999 Hz to it.
>>>> That way
>>>> -     *    if the clock we need is 60000001 Hz (~60 MHz) and DRM
>>>> tells us to
>>>> -     *    make 60000 kHz then the clock framework will actually give us
>>>> -     *    the right clock.
>>>> -     *
>>>> -     *    NOTE: if the PLL (maybe through a divider) could actually
>>>> make
>>>> -     *    a clock rate 999 Hz higher instead of the one we want then
>>>> this
>>>> -     *    could be a problem.  Unfortunately there's not much we can do
>>>> -     *    since it's baked into DRM to use kHz.  It shouldn't matter in
>>>> -     *    practice since Rockchip PLLs are controlled by tables and
>>>> -     *    even if there is a divider in the middle I wouldn't expect
>>>> PLL
>>>> -     *    rates in the table that are just a few kHz different.
>>>> -     *
>>>> -     * 2. Get the clock framework to round the rate for us to tell us
>>>> -     *    what it will actually make.
>>>> -     *
>>>> -     * 3. Store the rounded up rate so that we don't need to worry
>>>> about
>>>> -     *    this in the actual clk_set_rate().
>>>> -     */
>>>> -    rate = clk_round_rate(vop->dclk, adjusted_mode->clock * 1000 +
>>>> 999);
>>>> -    adjusted_mode->clock = DIV_ROUND_UP(rate, 1000);
>>>> -
>>>> -    return true;
>>>> -}
>>>> -
>>>>    static bool vop_dsp_lut_is_enabled(struct vop *vop)
>>>>    {
>>>>        return vop_read_reg(vop, 0, &vop->data->common->dsp_lut_en);
>>>> @@ -1512,7 +1468,6 @@ static void vop_crtc_atomic_flush(struct
>>>> drm_crtc *crtc,
>>>>    }
>>>>      static const struct drm_crtc_helper_funcs vop_crtc_helper_funcs = {
>>>> -    .mode_fixup = vop_crtc_mode_fixup,
>>>>        .atomic_check = vop_crtc_atomic_check,
>>>>        .atomic_begin = vop_crtc_atomic_begin,
>>>>        .atomic_flush = vop_crtc_atomic_flush,
>