Re: [PATCH] drm/bridge: tc358767: Expose test mode functionality via debugfs

[Andrey Smirnov]

On Mon, Aug 26, 2019 at 10:46 PM Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote:
>
> Hi,
>
> On 26/08/2019 21:25, Andrey Smirnov wrote:
> > Presently, the driver code artificially limits test pattern mode to a
> > single pattern with fixed color selection. It being a kernel module
> > parameter makes switching "test patter" <-> "proper output" modes
> > on-the-fly clunky and outright impossible if the driver is built into
> > the kernel.
> >
> > To improve the situation a bit, convert current test pattern code to
> > use debugfs instead by exposing "TestCtl" register. This way old
> > "tc_test_pattern=1" functionality can be emulated via:
> >
> >      echo -n 0x78146312 > tstctl
> >
> > and switch back to regular mode can be done with:
> >
> >      echo -n 0x78146310 > tstctl
>
> It might be worth explaining the format in the commit msg or in a
> comment in the driver.
>

Good point. Will do if this is the format going forward.

> > Note that switching to any of the test patterns, will NOT trigger link
> > re-establishment whereas switching to normal operation WILL. This is
> > done so:
> >
> > a) we can isolate and verify (e)DP link functionality by switching to
> >     one of the test patters
> >
> > b) trigger a link re-establishment by switching back to normal mode
> >
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
> > Cc: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> > Cc: Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx>
> > Cc: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
> > Cc: Cory Tusar <cory.tusar@xxxxxxxx>
> > Cc: Chris Healy <cphealy@xxxxxxxxx>
> > Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > ---
> >   drivers/gpu/drm/bridge/tc358767.c | 137 ++++++++++++++++++++++--------
> >   1 file changed, 101 insertions(+), 36 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> > index 6308d93ad91d..7a795b613ed0 100644
> > --- a/drivers/gpu/drm/bridge/tc358767.c
> > +++ b/drivers/gpu/drm/bridge/tc358767.c
> > @@ -17,6 +17,7 @@
> >
> >   #include <linux/bitfield.h>
> >   #include <linux/clk.h>
> > +#include <linux/debugfs.h>
> >   #include <linux/device.h>
> >   #include <linux/gpio/consumer.h>
> >   #include <linux/i2c.h>
> > @@ -222,11 +223,10 @@
> >   #define COLOR_B                     GENMASK(15, 8)
> >   #define ENI2CFILTER         BIT(4)
> >   #define COLOR_BAR_MODE              GENMASK(1, 0)
> > +#define COLOR_BAR_MODE_NORMAL        0
> >   #define COLOR_BAR_MODE_BARS 2
> > -#define PLL_DBG                      0x0a04
> >
> > -static bool tc_test_pattern;
> > -module_param_named(test, tc_test_pattern, bool, 0644);
> > +#define PLL_DBG                      0x0a04
> >
> >   struct tc_edp_link {
> >       struct drm_dp_link      base;
> > @@ -789,16 +789,6 @@ static int tc_set_video_mode(struct tc_data *tc,
> >       if (ret)
> >               return ret;
> >
> > -     /* Test pattern settings */
> > -     ret = regmap_write(tc->regmap, TSTCTL,
> > -                        FIELD_PREP(COLOR_R, 120) |
> > -                        FIELD_PREP(COLOR_G, 20) |
> > -                        FIELD_PREP(COLOR_B, 99) |
> > -                        ENI2CFILTER |
> > -                        FIELD_PREP(COLOR_BAR_MODE, COLOR_BAR_MODE_BARS));
> > -     if (ret)
> > -             return ret;
> > -
> >       /* DP Main Stream Attributes */
> >       vid_sync_dly = hsync_len + left_margin + mode->hdisplay;
> >       ret = regmap_write(tc->regmap, DP0_VIDSYNCDELAY,
> > @@ -1150,14 +1140,6 @@ static int tc_stream_enable(struct tc_data *tc)
> >
> >       dev_dbg(tc->dev, "enable video stream\n");
> >
> > -     /* PXL PLL setup */
> > -     if (tc_test_pattern) {
> > -             ret = tc_pxl_pll_en(tc, clk_get_rate(tc->refclk),
> > -                                 1000 * tc->mode.clock);
> > -             if (ret)
> > -                     return ret;
> > -     }
> > -
> >       ret = tc_set_video_mode(tc, &tc->mode);
> >       if (ret)
> >               return ret;
> > @@ -1186,12 +1168,8 @@ static int tc_stream_enable(struct tc_data *tc)
> >       if (ret)
> >               return ret;
> >       /* Set input interface */
> > -     value = DP0_AUDSRC_NO_INPUT;
> > -     if (tc_test_pattern)
> > -             value |= DP0_VIDSRC_COLOR_BAR;
> > -     else
> > -             value |= DP0_VIDSRC_DPI_RX;
> > -     ret = regmap_write(tc->regmap, SYSCTRL, value);
> > +     ret = regmap_write(tc->regmap, SYSCTRL,
> > +                        DP0_AUDSRC_NO_INPUT | DP0_VIDSRC_DPI_RX);
> >       if (ret)
> >               return ret;
> >
> > @@ -1220,39 +1198,44 @@ static void tc_bridge_pre_enable(struct drm_bridge *bridge)
> >       drm_panel_prepare(tc->panel);
> >   }
> >
> > -static void tc_bridge_enable(struct drm_bridge *bridge)
> > +static int __tc_bridge_enable(struct tc_data *tc)
> >   {
> > -     struct tc_data *tc = bridge_to_tc(bridge);
> >       int ret;
> >
> >       ret = tc_get_display_props(tc);
> >       if (ret < 0) {
> >               dev_err(tc->dev, "failed to read display props: %d\n", ret);
> > -             return;
> > +             return ret;
> >       }
> >
> >       ret = tc_main_link_enable(tc);
> >       if (ret < 0) {
> >               dev_err(tc->dev, "main link enable error: %d\n", ret);
> > -             return;
> > +             return ret;
> >       }
> >
> >       ret = tc_stream_enable(tc);
> >       if (ret < 0) {
> >               dev_err(tc->dev, "main link stream start error: %d\n", ret);
> >               tc_main_link_disable(tc);
> > -             return;
> >       }
> >
> > -     drm_panel_enable(tc->panel);
> > +     return ret;
> >   }
>
> Maybe it's just me, but I rather have the last if() block do a "return
> ret"; and have "return 0;" at the end of the function to keep all the if
> blocks consistent.

OK, will fix in v2.

>
> >
> > -static void tc_bridge_disable(struct drm_bridge *bridge)
> > +static void tc_bridge_enable(struct drm_bridge *bridge)
> >   {
> >       struct tc_data *tc = bridge_to_tc(bridge);
> > -     int ret;
> >
> > -     drm_panel_disable(tc->panel);
> > +     if (__tc_bridge_enable(tc) < 0)
> > +             return;
> > +
> > +     drm_panel_enable(tc->panel);
> > +}
> > +
> > +static int __tc_bridge_disable(struct tc_data *tc)
> > +{
> > +     int ret;
> >
> >       ret = tc_stream_disable(tc);
> >       if (ret < 0)
> > @@ -1261,6 +1244,16 @@ static void tc_bridge_disable(struct drm_bridge *bridge)
> >       ret = tc_main_link_disable(tc);
> >       if (ret < 0)
> >               dev_err(tc->dev, "main link disable error: %d\n", ret);
> > +
> > +     return ret;
> > +}
> > +
> > +static void tc_bridge_disable(struct drm_bridge *bridge)
> > +{
> > +     struct tc_data *tc = bridge_to_tc(bridge);
> > +
> > +     drm_panel_disable(tc->panel);
> > +     __tc_bridge_disable(tc);
> >   }
>
> Maybe have this enable/disable change as a separate patch?
>

Sure, I can do that in v2.

> >
> >   static void tc_bridge_post_disable(struct drm_bridge *bridge)
> > @@ -1372,6 +1365,77 @@ static enum drm_connector_status tc_connector_detect(struct drm_connector *conne
> >               return connector_status_disconnected;
> >   }
> >
> > +static int tc_tstctl_set(void *data, u64 val)
> > +{
> > +     struct tc_data *tc = data;
> > +     int ret;
> > +
> > +     if (FIELD_GET(COLOR_BAR_MODE, val) == COLOR_BAR_MODE_NORMAL) {
> > +             ret = regmap_write(tc->regmap, SYSCTRL, DP0_VIDSRC_DPI_RX);
> > +             if (ret) {
> > +                     dev_err(tc->dev,
> > +                             "failed to select dpi video stream\n");
> > +                     return ret;
> > +             }
> > +
> > +             ret = regmap_write(tc->regmap, TSTCTL, val | ENI2CFILTER);
> > +             if (ret) {
> > +                     dev_err(tc->dev, "failed to set TSTCTL\n");
> > +                     return ret;
> > +             }
> > +
> > +             ret = tc_pxl_pll_dis(tc);
> > +             if (ret) {
> > +                     dev_err(tc->dev, "failed to disable PLL\n");
> > +                     return ret;
> > +             }
> > +
> > +             /*
> > +              * Re-establish DP link
> > +              */
> > +             ret = __tc_bridge_disable(tc);
> > +             if (ret)
> > +                     return ret;
> > +
> > +             ret = __tc_bridge_enable(tc);
> > +             if (ret)
> > +                     return ret;
> > +     } else {
> > +             ret = tc_pxl_pll_en(tc, clk_get_rate(tc->refclk),
> > +                                 1000 * tc->mode.clock);
> > +             if (ret) {
> > +                     dev_err(tc->dev, "failed to enable PLL\n");
> > +                     return ret;
> > +             }
> > +
> > +             ret = regmap_write(tc->regmap, TSTCTL, val | ENI2CFILTER);
> > +             if (ret) {
> > +                     dev_err(tc->dev, "failed to set TSTCTL\n");
> > +                     return ret;
> > +             }
> > +
> > +             ret = regmap_write(tc->regmap, SYSCTRL, DP0_VIDSRC_COLOR_BAR);
> > +             if (ret) {
> > +                     dev_err(tc->dev, "failed to color bar video stream\n");
> > +                     return ret;
> > +             }
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +DEFINE_SIMPLE_ATTRIBUTE(tc_tstctl_fops, NULL, tc_tstctl_set, "%llu\n");
> > +
> > +static int tc_late_register(struct drm_connector *connector)
> > +{
> > +     if (connector->debugfs_entry)
> > +             debugfs_create_file_unsafe("tstctl", 0644,
> > +                                        connector->debugfs_entry,
> > +                                        connector_to_tc(connector),
> > +                                        &tc_tstctl_fops);
> > +     return 0;
> > +}
>
> I very recently wanted to add quick debugfs functionality to a bridge
> too, but as there didn't seem an easy way to do it, I just lazily added
> the debugfs files to the debugfs root...
>
> I'm not sure if adding bridge's debugfs files to connector's directory
> is a good idea. What if we have two bridges, both have the same debugfs
> file? Or even if there's no conflict, there's also no way to know which
> bridge a particular debugfs file belongs to.
>
> Maybe we need some DRM infrastructure for bridge debugfs?
>

I'll move to using a dedicated entry in debugfs, which should address
all of those concerns.

Thanks,
Andrey Smirnov