drm: bridge: samsung-dsim: Fix init during host transfer

In case the downstream bridge or panel uses DSI transfers before the
DSI host was actually initialized through samsung_dsim_atomic_enable()
which clears the stop state (LP11) mode, all transfers will fail.

This happens with downstream bridges that are controlled by DSI
commands such as the tc358762.

As documented in [1] DSI hosts are expected to allow transfers
outside the normal bridge enable/disable flow.

To fix this make sure that stop state is cleared in
samsung_dsim_host_transfer() which restores the previous
behavior.

We also factor out the common code to enable/disable stop state
to samsung_dsim_set_stop_state().

[1] https://docs.kernel.org/gpu/drm-kms-helpers.html#mipi-dsi-bridge-operation

Fixes: 0c14d3130654 ("drm: bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec")
Reported-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Tested-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230724151640.555490-1-frieder@fris.de

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 043b810..73ec607 100644 (file)
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1386,6 +1386,18 @@ static void samsung_dsim_disable_irq(struct samsung_dsim *dsi)
        disable_irq(dsi->irq);
 }
 
+static void samsung_dsim_set_stop_state(struct samsung_dsim *dsi, bool enable)
+{
+       u32 reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
+
+       if (enable)
+               reg |= DSIM_FORCE_STOP_STATE;
+       else
+               reg &= ~DSIM_FORCE_STOP_STATE;
+
+       samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
+}
+
 static int samsung_dsim_init(struct samsung_dsim *dsi)
 {
        const struct samsung_dsim_driver_data *driver_data = dsi->driver_data;
@@ -1445,15 +1457,12 @@ static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
                                       struct drm_bridge_state *old_bridge_state)
 {
        struct samsung_dsim *dsi = bridge_to_dsi(bridge);
-       u32 reg;
 
        if (samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) {
                samsung_dsim_set_display_mode(dsi);
                samsung_dsim_set_display_enable(dsi, true);
        } else {
-               reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
-               reg &= ~DSIM_FORCE_STOP_STATE;
-               samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
+               samsung_dsim_set_stop_state(dsi, false);
        }
 
        dsi->state |= DSIM_STATE_VIDOUT_AVAILABLE;
@@ -1463,16 +1472,12 @@ static void samsung_dsim_atomic_disable(struct drm_bridge *bridge,
                                        struct drm_bridge_state *old_bridge_state)
 {
        struct samsung_dsim *dsi = bridge_to_dsi(bridge);
-       u32 reg;
 
        if (!(dsi->state & DSIM_STATE_ENABLED))
                return;
 
-       if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) {
-               reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
-               reg |= DSIM_FORCE_STOP_STATE;
-               samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
-       }
+       if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type))
+               samsung_dsim_set_stop_state(dsi, true);
 
        dsi->state &= ~DSIM_STATE_VIDOUT_AVAILABLE;
 }
@@ -1775,6 +1780,8 @@ static ssize_t samsung_dsim_host_transfer(struct mipi_dsi_host *host,
        if (ret)
                return ret;
 
+       samsung_dsim_set_stop_state(dsi, false);
+
        ret = mipi_dsi_create_packet(&xfer.packet, msg);
        if (ret < 0)
                return ret;