6.6-stable review patch. If anyone has any objections, please let me know.
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From: Michael Walle mwalle@kernel.org
[ Upstream commit ff3d5d04db07e5374758baa7e877fde8d683ebab ]
The FORCE_STOP_STATE bit is unsuitable to force the DSI link into LP-11 mode. It seems the bridge internally queues DSI packets and when the FORCE_STOP_STATE bit is cleared, they are sent in close succession without any useful timing (this also means that the DSI lanes won't go into LP-11 mode). The length of this gibberish varies between 1ms and 5ms. This sometimes breaks an attached bridge (TI SN65DSI84 in this case). In our case, the bridge will fail in about 1 per 500 reboots.
The FORCE_STOP_STATE handling was introduced to have the DSI lanes in LP-11 state during the .pre_enable phase. But as it turns out, none of this is needed at all. Between samsung_dsim_init() and samsung_dsim_set_display_enable() the lanes are already in LP-11 mode. The code as it was before commit 20c827683de0 ("drm: bridge: samsung-dsim: Fix init during host transfer") and 0c14d3130654 ("drm: bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec") was correct in this regard.
This patch basically reverts both commits. It was tested on an i.MX8M SoC with an SN65DSI84 bridge. The signals were probed and the DSI packets were decoded during initialization and link start-up. After this patch the first DSI packet on the link is a VSYNC packet and the timing is correct.
Command mode between .pre_enable and .enable was also briefly tested by a quick hack. There was no DSI link partner which would have responded, but it was made sure the DSI packet was send on the link. As a side note, the command mode seems to just work in HS mode. I couldn't find that the bridge will handle commands in LP mode.
Fixes: 20c827683de0 ("drm: bridge: samsung-dsim: Fix init during host transfer") Fixes: 0c14d3130654 ("drm: bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec") Signed-off-by: Michael Walle mwalle@kernel.org Signed-off-by: Inki Dae inki.dae@samsung.com Link: https://patchwork.freedesktop.org/patch/msgid/20231113164344.1612602-1-mwall... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/bridge/samsung-dsim.c | 32 ++------------------------- 1 file changed, 2 insertions(+), 30 deletions(-)
diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c index 19bdb32dbc9a..f24666b48193 100644 --- a/drivers/gpu/drm/bridge/samsung-dsim.c +++ b/drivers/gpu/drm/bridge/samsung-dsim.c @@ -941,10 +941,6 @@ static int samsung_dsim_init_link(struct samsung_dsim *dsi) reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG); reg &= ~DSIM_STOP_STATE_CNT_MASK; reg |= DSIM_STOP_STATE_CNT(driver_data->reg_values[STOP_STATE_CNT]); - - if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) - reg |= DSIM_FORCE_STOP_STATE; - samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
reg = DSIM_BTA_TIMEOUT(0xff) | DSIM_LPDR_TIMEOUT(0xffff); @@ -1401,18 +1397,6 @@ 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; @@ -1462,9 +1446,6 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge, ret = samsung_dsim_init(dsi); if (ret) return; - - samsung_dsim_set_display_mode(dsi); - samsung_dsim_set_display_enable(dsi, true); } }
@@ -1473,12 +1454,8 @@ static void samsung_dsim_atomic_enable(struct drm_bridge *bridge, { struct samsung_dsim *dsi = bridge_to_dsi(bridge);
- 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 { - samsung_dsim_set_stop_state(dsi, false); - } + samsung_dsim_set_display_mode(dsi); + samsung_dsim_set_display_enable(dsi, true);
dsi->state |= DSIM_STATE_VIDOUT_AVAILABLE; } @@ -1491,9 +1468,6 @@ static void samsung_dsim_atomic_disable(struct drm_bridge *bridge, if (!(dsi->state & DSIM_STATE_ENABLED)) return;
- if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) - samsung_dsim_set_stop_state(dsi, true); - dsi->state &= ~DSIM_STATE_VIDOUT_AVAILABLE; }
@@ -1795,8 +1769,6 @@ 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;