Re: [PATCH v8 06/14] drm: bridge: samsung-dsim: Handle proper DSI host initialization

[Marek Vasut]

On 11/10/22 19:38, Jagan Teki wrote:
DSI host initialization handling in previous exynos dsi driver has
some pitfalls. It initializes the host during host transfer() hook
that is indeed not the desired call flow for I2C and any other DSI
configured downstream bridges.
Host transfer() is usually triggered for downstream DSI panels or
bridges and I2C-configured-DSI bridges miss these host initialization
as these downstream bridges use bridge operations hooks like pre_enable,
and enable in order to initialize or set up the host.

This patch is trying to handle the host init handler to satisfy all
downstream panels and bridges. Added the DSIM_STATE_REINITIALIZED state
flag to ensure that host init is also done on first cmd transfer, this
helps existing DSI panels work on exynos platform (form Marek
Szyprowski).

v8, v7, v6, v5:
* none

v4:
* update init handling to ensure host init done on first cmd transfer

v3:
* none

v2:
* check initialized state in samsung_dsim_init

v1:
* keep DSI init in host transfer

Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com>
Signed-off-by: Jagan Teki <ja...@amarulasolutions.com>
---
  drivers/gpu/drm/bridge/samsung-dsim.c | 25 +++++++++++++++++--------
  include/drm/bridge/samsung-dsim.h     |  5 +++--
  2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c 
b/drivers/gpu/drm/bridge/samsung-dsim.c
index bb1f45fd5a88..ec7e01ae02ea 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1234,12 +1234,17 @@ static void samsung_dsim_disable_irq(struct 
samsung_dsim *dsi)
        disable_irq(dsi->irq);
  }
  
-static int samsung_dsim_init(struct samsung_dsim *dsi)
+static int samsung_dsim_init(struct samsung_dsim *dsi, unsigned int flag)
  {
        const struct samsung_dsim_driver_data *driver_data = dsi->driver_data;
  
+	if (dsi->state & flag)
+               return 0;
+
        samsung_dsim_reset(dsi);
-       samsung_dsim_enable_irq(dsi);
+
+       if (!(dsi->state & DSIM_STATE_INITIALIZED))
+               samsung_dsim_enable_irq(dsi);
  
  	if (driver_data->reg_values[RESET_TYPE] == DSIM_FUNCRST)
                samsung_dsim_enable_lane(dsi, BIT(dsi->lanes) - 1);
@@ -1250,6 +1255,8 @@ static int samsung_dsim_init(struct samsung_dsim *dsi)
        samsung_dsim_set_phy_ctrl(dsi);
        samsung_dsim_init_link(dsi);
  
+	dsi->state |= flag;
+
        return 0;
  }
  
@@ -1269,6 +1276,10 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
        }
  
  	dsi->state |= DSIM_STATE_ENABLED;
+
+       ret = samsung_dsim_init(dsi, DSIM_STATE_INITIALIZED);
+       if (ret)
+               return;
  }
  
  static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
@@ -1458,12 +1469,9 @@ static ssize_t samsung_dsim_host_transfer(struct 
mipi_dsi_host *host,
        if (!(dsi->state & DSIM_STATE_ENABLED))
                return -EINVAL;
  
-	if (!(dsi->state & DSIM_STATE_INITIALIZED)) {
-               ret = samsung_dsim_init(dsi);
-               if (ret)
-                       return ret;
-               dsi->state |= DSIM_STATE_INITIALIZED;
-       }
+       ret = samsung_dsim_init(dsi, DSIM_STATE_REINITIALIZED);

This triggers full controller reset and reprogramming upon first command 
transfer, is such heavy handed reload really necessary ?