linux-kernel - Re: [v3 4/6] drm/vs: Add KMS crtc&plane

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Date:   Thu, 7 Dec 2023 19:31:43 +0800
From:   Keith Zhao <keith.zhao@...rfivetech.com>
To:     Icenowy Zheng <uwu@...nowy.me>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>
CC:     "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "suijingfeng@...ngson.cn" <suijingfeng@...ngson.cn>,
        "tzimmermann@...e.de" <tzimmermann@...e.de>,
        "paul.walmsley@...ive.com" <paul.walmsley@...ive.com>,
        "mripard@...nel.org" <mripard@...nel.org>,
        Xingyu Wu <xingyu.wu@...rfivetech.com>,
        Jack Zhu <jack.zhu@...rfivetech.com>,
        "palmer@...belt.com" <palmer@...belt.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        William Qiu <william.qiu@...rfivetech.com>,
        Shengyang Chen <shengyang.chen@...rfivetech.com>,
        Changhuang Liang <changhuang.liang@...rfivetech.com>
Subject: Re: [v3 4/6] drm/vs: Add KMS crtc&plane



On 2023/12/7 16:41, Icenowy Zheng wrote:
> 在 2023-12-04星期一的 20:33 +0800，Keith Zhao写道：
> *snip*
> 
>> +static void update_cursor_plane(struct vs_dc *dc, struct vs_plane
>> *plane,
>> +                               struct drm_plane *drm_plane,
>> +                               struct drm_atomic_state *drm_state)
>> +{
>> +       struct drm_plane_state *state =
>> drm_atomic_get_new_plane_state(drm_state,
>> +                                                                    
>>   drm_plane);
>> +       struct vs_plane_state *plane_state =
>> to_vs_plane_state(state);
>> +       struct drm_framebuffer *drm_fb = state->fb;
>> +       struct dc_hw_cursor cursor;
>> +
>> +       cursor.address = plane_state->dma_addr[0];
>> +       cursor.x = state->crtc_x;
>> +       cursor.y = state->crtc_y;
> 
> From my experiments on poking with registers on T-Head TH1520 (also
> uses DC8200 display controller and a similar driver), the DC8200
> hardware have a different definition of cursor position X and Y with
> the CRTC plane state.
> 
> For CRTC plane state, hot_x and hot_y are only provided as reference,
> and the cursor should be displayed with its (0,0) drawn to (crtc_x,
> crtc_y) ([XY]_crtc are values specified in CRTC state, the right part
> of the assignments here), when the cursor is moved to (0,0) but the hot
> point is not (0,0), it could be negative.
> 
> However, for DC8200 registers definition, cursor XY position could not
> be negative -- the cursor will disappear then; because in its
> definition, the cursor XY position should be where the cursor is
> pointing to, instead of its (0,0). DC8200 will draw (0,0) of the cursor
> to (x - hot_x, y - hot_y). So to met the expectation of the KMS plane
> settings, the DC8200 position should be set to (crtc_x + hot_x, crtc_y
> + hot_y) instead. Thus these two lines of code should be:
> 
> ```
>         cursor.x = state->crtc_x + drm_fb->hot_x;
>         cursor.y = state->crtc_y + drm_fb->hot_y;
> ```
> 
> 
>> +       cursor.hot_x = drm_fb->hot_x;
>> +       cursor.hot_y = drm_fb->hot_y;
>> +       cursor.display_id = to_vs_display_id(dc, state->crtc);
>> +       update_cursor_size(state, &cursor);
>> +       cursor.enable = true;
>> +
>> +       dc_hw_update_cursor(&dc->hw, cursor.display_id, &cursor);
>> +}
> *snip
hello Icenowy:
you are deep understanding on dc8200.
by the way of practice
I tested this change on the debian desktop, is there a way to compare the cursor behavior change?
Thanks