[PATCH v8 09/14] drm: bridge: samsung-dsim: Add atomic_get_input_bus_fmts

[Marek Vasut]

On 11/14/22 08:49, Jagan Teki wrote:
> On Sun, Nov 13, 2022 at 5:51 AM Marek Vasut <marex at denx.de> wrote:
>>
>> On 11/10/22 19:38, Jagan Teki wrote:
>>> Finding the right input bus format throughout the pipeline is hard
>>> so add atomic_get_input_bus_fmts callback and initialize with the
>>> proper input format from list of supported output formats.
>>>
>>> This format can be used in pipeline for negotiating bus format between
>>> the DSI-end of this bridge and the other component closer to pipeline
>>> components.
>>>
>>> List of Pixel formats are taken from,
>>> AN13573 i.MX 8/RT MIPI DSI/CSI-2, Rev. 0, 21 March 2022
>>> 3.7.4 Pixel formats
>>> Table 14. DSI pixel packing formats
>>>
>>> v8:
>>> * added pixel formats supported by NXP AN13573 i.MX 8/RT MIPI DSI/CSI-2
>>>
>>> v7, v6, v5, v4:
>>> * none
>>>
>>> v3:
>>> * include media-bus-format.h
>>>
>>> v2:
>>> * none
>>>
>>> v1:
>>> * new patch
>>>
>>> Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
>>> ---
>>>    drivers/gpu/drm/bridge/samsung-dsim.c | 53 +++++++++++++++++++++++++++
>>>    1 file changed, 53 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
>>> index 0fe153b29e4f..33e5ae9c865f 100644
>>> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
>>> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
>>> @@ -15,6 +15,7 @@
>>>    #include <linux/clk.h>
>>>    #include <linux/delay.h>
>>>    #include <linux/irq.h>
>>> +#include <linux/media-bus-format.h>
>>>    #include <linux/of_device.h>
>>>    #include <linux/phy/phy.h>
>>>
>>> @@ -1321,6 +1322,57 @@ static void samsung_dsim_atomic_post_disable(struct drm_bridge *bridge,
>>>        pm_runtime_put_sync(dsi->dev);
>>>    }
>>>
>>> +/*
>>> + * This pixel output formats list referenced from,
>>> + * AN13573 i.MX 8/RT MIPI DSI/CSI-2, Rev. 0, 21 March 2022
>>> + * 3.7.4 Pixel formats
>>> + * Table 14. DSI pixel packing formats
>>> + */
>>> +static const u32 samsung_dsim_pixel_output_fmts[] = {
>>
>> You can also add :
>>
>> MEDIA_BUS_FMT_YUYV10_1X20
>>
>> MEDIA_BUS_FMT_YUYV12_1X24
> 
> Are these for the below formats?
> 
> "Loosely Packed Pixel Stream, 20-bit YCbCr, 4:2:2
>   Packed Pixel Stream, 24-bit YCbCr, 4:2:2"
>>
>>> +     MEDIA_BUS_FMT_UYVY8_1X16,
>>> +     MEDIA_BUS_FMT_RGB101010_1X30,
>>> +     MEDIA_BUS_FMT_RGB121212_1X36,
>>> +     MEDIA_BUS_FMT_RGB565_1X16,
>>> +     MEDIA_BUS_FMT_RGB666_1X18,
>>> +     MEDIA_BUS_FMT_RGB888_1X24,
>>> +};
>>> +
>>> +static bool samsung_dsim_pixel_output_fmt_supported(u32 fmt)
>>> +{
>>> +     int i;
>>> +
>>> +     for (i = 0; i < ARRAY_SIZE(samsung_dsim_pixel_output_fmts); i++) {
>>> +             if (samsung_dsim_pixel_output_fmts[i] == fmt)
>>> +                     return true;
>>> +     }
>>> +
>>> +     return false;
>>> +}
>>> +
>>> +static u32 *
>>> +samsung_dsim_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>>> +                                    struct drm_bridge_state *bridge_state,
>>> +                                    struct drm_crtc_state *crtc_state,
>>> +                                    struct drm_connector_state *conn_state,
>>> +                                    u32 output_fmt,
>>> +                                    unsigned int *num_input_fmts)
>>> +{
>>> +     u32 *input_fmts;
>>> +
>>> +     if (!samsung_dsim_pixel_output_fmt_supported(output_fmt))
>>> +             return NULL;
>>> +
>>> +     *num_input_fmts = 1;
>>
>> Shouldn't this be 6 ?
>>
>>> +     input_fmts = kmalloc(sizeof(*input_fmts), GFP_KERNEL);
>>> +     if (!input_fmts)
>>> +             return NULL;
>>> +
>>> +     input_fmts[0] = output_fmt;
>>
>> Shouldn't this be a list of all 6 supported pixel formats ?
> 
> Negotiation would settle to return one input_fmt from the list of
> supporting output_fmts. so the num_input_fmts would be 1 rather than
> the number of fmts in the supporting list. This is what I understood
> from the atomic_get_input_bus_fmts API. let me know if I miss
> something here.

How does the negotiation work for this kind of pipeline:

LCDIFv3<->DSIM<->HDMI bridge<->HDMI connector

where all elements (LCDIFv3, DSIM, HDMI bridge) can support either 
RGB888 or packed YUV422 ?

Who decides the format used by such pipeline ?

Why should it be the DSIM bridge and not e.g. the HDMI bridge or the 
LCDIFv3 ?