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From:   Vinay Simha B N <simhavcs@gmail.com>
Date:   Wed, 12 Aug 2020 20:25:23 +0530
Message-ID: <CAGWqDJ6eHCNXb5dMCUJ785iUp7gjdCk0bB=GuZesVesaVACucQ@mail.gmail.com>
Subject: Re: [PATCH] drm/bridge/tc358775: Fixes bus formats read
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Andrzej Hajda <a.hajda@samsung.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        "open list:DRM DRIVERS" <dri-devel@lists.freedesktop.org>,
        open list <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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laurent,

Video data input format :  RGB666 loosely packed 24 bits per pixel
Can we use MEDIA_BUS_FMT_RGB666_1X24_CPADHI? There was no information
wrt CPADHI or for loosely packed

static const u32 tc_lvds_in_bus_fmts[] = {
        MEDIA_BUS_FMT_RGB565_1X16,
        MEDIA_BUS_FMT_RGB666_1X18,
        MEDIA_BUS_FMT_RGB666_1X24_CPADHI,
        MEDIA_BUS_FMT_RBG888_1X24,
};

for (i = 0; i < ARRAY_SIZE(tc_lvds_in_bus_fmts); ++i)
                input_fmts[i] = tc_lvds_in_bus_fmts[i];
>> This will have all the available input formats, but finally which video data input format chosen?
Since dsi->format = MIPI_DSI_FMT_RGB888 is used does it chooses
MEDIA_BUS_FMT_RBG888_1X24 by the drm pipeline

On Wed, Aug 12, 2020 at 6:48 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Vinay,
>
> On Wed, Aug 12, 2020 at 06:07:52PM +0530, Vinay Simha B N wrote:
> > On Wed, Aug 12, 2020 at 3:24 PM Laurent Pinchart wrote:
> > > On Wed, Aug 12, 2020 at 12:55:50PM +0530, Vinay Simha BN wrote:
> > > > - bus formats read from drm_bridge_state.output_bus_cfg.format
> > > >   and .atomic_get_input_bus_fmts() instead of connector
> > > >
> > > > Signed-off-by: Vinay Simha BN <simhavcs@gmail.com>
> > > >
> > > > ---
> > > >  v1:
> > > >  * Laurent Pinchart review comments incorporated
> > > >    drm_bridge_state.output_bus_cfg.format
> > > >    instead of connector
> > > > ---
> > > >  drivers/gpu/drm/bridge/tc358775.c | 76 ++++++++++++++++++++++++++++++---------
> > > >  1 file changed, 59 insertions(+), 17 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/bridge/tc358775.c b/drivers/gpu/drm/bridge/tc358775.c
> > > > index 7da15cd..5d8714a 100644
> > > > --- a/drivers/gpu/drm/bridge/tc358775.c
> > > > +++ b/drivers/gpu/drm/bridge/tc358775.c
> > > > @@ -271,6 +271,13 @@ struct tc_data {
> > > >       struct gpio_desc        *stby_gpio;
> > > >       u8                      lvds_link; /* single-link or dual-link */
> > > >       u8                      bpc;
> > > > +     u32                     output_bus_fmt;
> > > > +};
> > > > +
> > > > +static const u32 tc_lvds_out_bus_fmts[] = {
> > > > +     MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA,
> > > > +     MEDIA_BUS_FMT_RGB888_1X7X4_SPWG,
> > > > +     MEDIA_BUS_FMT_RGB666_1X7X3_SPWG,
> > > >  };
> > > >
> > > >  static inline struct tc_data *bridge_to_tc(struct drm_bridge *b)
> > > > @@ -359,19 +366,6 @@ static void d2l_write(struct i2c_client *i2c, u16 addr, u32 val)
> > > >                       ret, addr);
> > > >  }
> > > >
> > > > -/* helper function to access bus_formats */
> > > > -static struct drm_connector *get_connector(struct drm_encoder *encoder)
> > > > -{
> > > > -     struct drm_device *dev = encoder->dev;
> > > > -     struct drm_connector *connector;
> > > > -
> > > > -     list_for_each_entry(connector, &dev->mode_config.connector_list, head)
> > > > -             if (connector->encoder == encoder)
> > > > -                     return connector;
> > > > -
> > > > -     return NULL;
> > > > -}
> > > > -
> > > >  static void tc_bridge_enable(struct drm_bridge *bridge)
> > > >  {
> > > >       struct tc_data *tc = bridge_to_tc(bridge);
> > > > @@ -380,7 +374,6 @@ static void tc_bridge_enable(struct drm_bridge *bridge)
> > > >       u32 val = 0;
> > > >       u16 dsiclk, clkdiv, byteclk, t1, t2, t3, vsdelay;
> > > >       struct drm_display_mode *mode;
> > > > -     struct drm_connector *connector = get_connector(bridge->encoder);
> > > >
> > > >       mode = &bridge->encoder->crtc->state->adjusted_mode;
> > > >
> > > > @@ -451,14 +444,13 @@ static void tc_bridge_enable(struct drm_bridge *bridge)
> > > >       d2l_write(tc->i2c, LVPHY0, LV_PHY0_PRBS_ON(4) | LV_PHY0_ND(6));
> > > >
> > > >       dev_dbg(tc->dev, "bus_formats %04x bpc %d\n",
> > > > -             connector->display_info.bus_formats[0],
> > > > +             tc->output_bus_fmt,
> > > >               tc->bpc);
> > > >       /*
> > > >        * Default hardware register settings of tc358775 configured
> > > >        * with MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA jeida-24 format
> > > >        */
> > > > -     if (connector->display_info.bus_formats[0] ==
> > > > -             MEDIA_BUS_FMT_RGB888_1X7X4_SPWG) {
> > > > +     if (tc->output_bus_fmt == MEDIA_BUS_FMT_RGB888_1X7X4_SPWG) {
> > > >               /* VESA-24 */
> > > >               d2l_write(tc->i2c, LV_MX0003, LV_MX(LVI_R0, LVI_R1, LVI_R2, LVI_R3));
> > > >               d2l_write(tc->i2c, LV_MX0407, LV_MX(LVI_R4, LVI_R7, LVI_R5, LVI_G0));
> > > > @@ -590,6 +582,51 @@ static int tc358775_parse_dt(struct device_node *np, struct tc_data *tc)
> > > >       return 0;
> > > >  }
> > > >
> > > > +static int tc_bridge_atomic_check(struct drm_bridge *bridge,
> > > > +                               struct drm_bridge_state *bridge_state,
> > > > +                               struct drm_crtc_state *crtc_state,
> > > > +                               struct drm_connector_state *conn_state)
> > > > +{
> > > > +     struct tc_data *tc = bridge_to_tc(bridge);
> > > > +
> > > > +     tc->output_bus_fmt = bridge_state->output_bus_cfg.format;
> > >
> > > .atomic_check() isn't allowed to modify the device state, neither the
> > > hardware state nor the software state in drm_bridge or tc_data. You can
> > > instead access the bridge state directly in tc_bridge_enable(), with
> > >
> > >         struct drm_bridge_state *state =
> > >                 drm_priv_to_bridge_state(bridge->base.state);
> >
> > Currently the driver is picking up from the dts panel
> > (data-mapping = "vesa-24";) or jeida-24 or jeida-18.
> >
> > Does state->output_bus_cfg.format  get set from the data-mapping?
>
> It should. The drm_panel should take care of that. In
> panel_simple_get_non_edid_modes(), it calls
>
>         if (panel->desc->bus_format)
>                 drm_display_info_set_bus_formats(&connector->display_info,
>                                                  &panel->desc->bus_format, 1);
>
> to initialize the bus format in display_info. Then, the DRM bridge
> helper drm_atomic_bridge_chain_select_bus_fmts() retrieves the output
> format by calling .atomic_get_output_bus_fmts() if implemented by the
> last bridge in the chain, or directly from the connector display_info.
> The last bridge in the chain is a DRM panel bridge, and doesn't
> implement .atomic_get_output_bus_fmts(), so the format from display_info
> is used, and is stored in the output_bus_cfg.format field of this bridge
> in select_bus_fmt_recursive().
>
> If something doesn't work according to the plan, I can help you
> debugging.
>
> > > > +
> > > > +     dev_dbg(tc->dev, "output_bus_fmt %04x\n", tc->output_bus_fmt);
> > > > +
> > > > +     return 0;
> > > > +}
> > > > +
> > > > +static u32 *
> > > > +tc_bridge_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 = NULL;
> > > > +     int i;
> > >
> > > i only takes positive values, so it can be an unsigned int.
> > >
> > > > +
> > > > +     *num_input_fmts = 0;
> > > > +
> > > > +     for (i = 0 ; i < ARRAY_SIZE(tc_lvds_out_bus_fmts) ; ++i) {
> > > > +             if (output_fmt == tc_lvds_out_bus_fmts[i]) {
> > > > +                     *num_input_fmts = 1;
> > > > +                     input_fmts = kcalloc(*num_input_fmts,
> > > > +                                          sizeof(*input_fmts),
> > > > +                                          GFP_KERNEL);
> > > > +                     if (!input_fmts)
> > > > +                             return NULL;
> > > > +
> > > > +                     input_fmts[0] = output_fmt;
> > >
> > > I don't think this is right, the input of the bridge isn't LVDS, is it ?
> >
> > Input to the bridge is DSI, format is already set
> >
> > dsi->format = MIPI_DSI_FMT_RGB888;
> >
> > enum mipi_dsi_pixel_format {
> >         MIPI_DSI_FMT_RGB888,
> >         MIPI_DSI_FMT_RGB666,
> >         MIPI_DSI_FMT_RGB666_PACKED,
> >         MIPI_DSI_FMT_RGB565,
> > };
> > include/drm/drm_mipi_dsi.h
> >
> > Why do we require this atomic_get_input_bus_fmts?
> >
> > Do i need to implement both atomic_get_input_bus_fmts and
> > atomic_get_output_bus_fmts?
>
> .atomic_get_output_bus_fmts() is only need for the last bridge in the
> chain, and is not mandatory when that bridge supports a single format.
> As this bridge can't be last (if the output is connect to a panel, there
> will be a drm_bridge wrapping the drm_panel), you don't have to
> implement that operation.
>
> .atomic_get_input_bus_fmts() is used to negotiate formats along the
> pipeline. The helps the DRM bridge helpers figure out what formats are
> possible, with the help of bridges that must report what input formats
> are compatible with a given output format. The DRM bridge helpers will
> take care of the rest.
>
> So, for this bridge, the input and output formats are decoupled. The
> bridge can output any of the three supported LVDS formats, regardless of
> what format it gets at its input. You should thus verify that the output
> format you receive in this function is supported (and return NULL if it
> isn't), and then return the list of supported input formats. If you
> don't implement .atomic_get_input_bus_fmts(), then the DRM bridge
> helpers will consider that the input and output formats are the same,
> and will set the output format of the previous bridge to, for example,
> MEDIA_BUS_FMT_RGB666_1X7X3_SPWG. It may work if the previous bridge
> doesn't care about its output format, but if it does, then it will be
> puzzled, as the previous bridge outputs DSI, not LVDS.
>
> > > As far as I can tell, the hardware support transcoding any of the
> > > supported input formats (RGB565, RGB666 or RGB888) to any of the
> > > supported output formats. How about the following ?
> > >
> > > static const u32 tc_lvds_in_bus_fmts[] = {
> > >         MEDIA_BUS_FMT_RGB565_1X16,
> > >         MEDIA_BUS_FMT_RGB666_1X18,
> > >         MEDIA_BUS_FMT_RBG888_1X24,
> > > };
> > >
> > > ...
> > >
> > >         u32 *input_fmts;
> > >         unsigned int i;
> > >
> > >         *num_input_fmts = 0;
> > >
> > >         for (i = 0 ; i < ARRAY_SIZE(tc_lvds_out_bus_fmts) ; ++i) {
> > >                 if (output_fmt == tc_lvds_out_bus_fmts[i])
> > >                         break;
> > >         }
> > >
> > >         if (i == ARRAY_SIZE(tc_lvds_out_bus_fmts))
> > >                 return NULL;
> > >
> > >         input_fmts = kcalloc(*num_input_fmts, ARRAY_SIZE(tc_lvds_in_bus_fmts),
> > >                              GFP_KERNEL);
> > >         if (!input_fmts)
> > >                 return NULL;
> > >
> > >         for (i = 0; i < ARRAY_SIZE(tc_lvds_in_bus_fmts); ++i)
> > >                 input_fmts[i] = tc_lvds_in_bus_fmts[i];
> > >
> > >         *num_inputs_fmts = ARRAY_SIZE(tc_lvds_in_bus_fmts);
> > >         return input_fmts;
> > >
> > > > +
> > > > +                     break;
> > > > +             }
> > > > +     }
> > > > +
> > > > +     return input_fmts;
> > > > +}
> > > > +
> > > >  static int tc_bridge_attach(struct drm_bridge *bridge,
> > > >                           enum drm_bridge_attach_flags flags)
> > > >  {
> > > > @@ -639,6 +676,11 @@ static int tc_bridge_attach(struct drm_bridge *bridge,
> > > >  }
> > > >
> > > >  static const struct drm_bridge_funcs tc_bridge_funcs = {
> > > > +     .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> > > > +     .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
> > > > +     .atomic_reset = drm_atomic_helper_bridge_reset,
> > > > +     .atomic_get_input_bus_fmts = tc_bridge_get_input_bus_fmts,
> > > > +     .atomic_check = tc_bridge_atomic_check,
> > > >       .attach = tc_bridge_attach,
> > > >       .pre_enable = tc_bridge_pre_enable,
> > > >       .enable = tc_bridge_enable,
>
> --
> Regards,
>
> Laurent Pinchart


-- 
regards,
vinaysimha