Re: [PATCH 2/2] drm: renesas: rzg2l_mipi_dsi: Fix the power-on sequence
From: Tommaso Merciai
Date: Tue Mar 17 2026 - 12:40:44 EST
Hi Biju,
Thanks for your comments.
On 3/17/26 17:16, Biju Das wrote:
Hi Tommaso Merciai,
-----Original Message-----
From: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>
Sent: 17 March 2026 16:05
Subject: Re: [PATCH 2/2] drm: renesas: rzg2l_mipi_dsi: Fix the power-on sequence
Hi Biju,
Thanks for your patch.
On Tue, Mar 17, 2026 at 12:36:01PM +0000, Biju wrote:
From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>drm_bridge *bridge,
Move reset_control_deassert() and reset_control_assert() from
rzg2l_mipi_dsi_dphy_init()/rzg2l_mipi_dsi_dphy_exit() to
atomic_pre_enable() and atomic_post_disable() respectively, and move
rzg2l_mipi_dsi_set_display_timing() from atomic_pre_enable() to
atomic_enable(), to align with the power-on sequence described in
Figure 34.5 of section "34.4.2.1 Reset" of the RZ/G2L hardware manual
Rev.1.50 May 2025.
According to the hardware manual, LINK registers must be written
before deasserting CMN_RSTB, and the 1ms delay is retained in
atomic_pre_enable() after the deassert.
Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
---
.../gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c | 27 +++++++++++--------
1 file changed, 16 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
index e53b48e4de56..9053ce037b75 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
@@ -484,7 +484,6 @@ static int rzg2l_mipi_dsi_dphy_init(struct rzg2l_mipi_dsi *dsi,
u32 dphytim1;
u32 dphytim2;
u32 dphytim3;
- int ret;
/* All DSI global operation timings are set with recommended setting */
for (i = 0; i < ARRAY_SIZE(rzg2l_mipi_dsi_global_timings); ++i) { @@
-524,12 +523,6 @@ static int rzg2l_mipi_dsi_dphy_init(struct rzg2l_mipi_dsi *dsi,
rzg2l_mipi_dsi_phy_write(dsi, DSIDPHYTIM2, dphytim2);
rzg2l_mipi_dsi_phy_write(dsi, DSIDPHYTIM3, dphytim3);
- ret = reset_control_deassert(dsi->rstc);
- if (ret < 0)
- return ret;
-
- fsleep(1000);
-
return 0;
}
@@ -541,8 +534,6 @@ static void rzg2l_mipi_dsi_dphy_exit(struct
rzg2l_mipi_dsi *dsi)
dphyctrl0 &= ~(DSIDPHYCTRL0_EN_LDO1200 | DSIDPHYCTRL0_EN_BGR);
rzg2l_mipi_dsi_phy_write(dsi, DSIDPHYCTRL0, dphyctrl0);
-
- reset_control_assert(dsi->rstc);
}
static int rzg2l_dphy_conf_clks(struct rzg2l_mipi_dsi *dsi, unsigned
long mode_freq, @@ -1030,24 +1021,37 @@ static void rzg2l_mipi_dsi_atomic_pre_enable(struct
connector = drm_atomic_get_new_connector_for_encoder(state, bridge->encoder);
crtc = drm_atomic_get_new_connector_state(state, connector)->crtc;
mode = &drm_atomic_get_new_crtc_state(state, crtc)->adjusted_mode;
-
ret = rzg2l_mipi_dsi_startup(dsi, mode);
if (ret < 0)
return;
- rzg2l_mipi_dsi_set_display_timing(dsi, mode);
+ ret = reset_control_deassert(dsi->rstc);
+ if (ret < 0)
+ return;
+
+ if (dsi->rstc)
+ fsleep(1000);
What about?
if (dsi->rstc) {
ret = reset_control_deassert(dsi->rstc);
if (ret < 0)
return;
fsleep(1000);
}
OK.
}
static void rzg2l_mipi_dsi_atomic_enable(struct drm_bridge *bridge,
struct drm_atomic_state *state) {
struct rzg2l_mipi_dsi *dsi = bridge_to_rzg2l_mipi_dsi(bridge);
+ const struct drm_display_mode *mode;
+ struct drm_connector *connector;
+ struct drm_crtc *crtc;
int ret;
ret = rzg2l_mipi_dsi_start_hs_clock(dsi);
if (ret < 0)
goto err_stop;
+ connector = drm_atomic_get_new_connector_for_encoder(state, bridge->encoder);
+ crtc = drm_atomic_get_new_connector_state(state, connector)->crtc;
+ mode = &drm_atomic_get_new_crtc_state(state, crtc)->adjusted_mode;
+
+ rzg2l_mipi_dsi_set_display_timing(dsi, mode);
+
Manual/Patch says that LINK registers must be written before deasserting CMN_RSTB:
NOT ALL.
Only these link registers.
− TXSETR
− ULPSSETR
− DSISETR
− CLSTPTSETR
− LPTRNSTSETR
atomic_pre_enable():
startup() (F) PHY timing regs + LINK
set_display_timing() (F) writing VICH1* (LINK regs)
This is not F. This is after starting HS CLK.
reset_control_deassert() (G)
fsleep(1000) (H)
Before this series we have:
atomic_pre_enable():
startup()
dphy_init()
write DSIDPHYTIMx (F) PHY timing regs
reset_control_deassert() (G) deassert CMN_RSTB
udelay(1) (H)
set_display_timing() (F) writing VICH1* (LINK regs)
This is not F. This is after starting HS CLK.
Moving set_display_timing() here you are setting LINK regs after
reset_control_deassert() and the sequence will be:
atomic_pre_enable():
startup() (F) PHY timing regs + LINK
reset_control_deassert() (G) CMN_RSTB deassert
fsleep(1000) (H) wait 1ms
atomic_enable():
start_hs_clock()
set_display_timing() (F) writing VICH1* (LINK regs)
This is not F. It is after starting HSCLK and it is as per hardware manual.
start_video()
I think to provide the right sequence we need to just move
reset_control_deassert(dsi->rstc);
From rzg2l_mipi_dsi_dphy_init() to rzg2l_mipi_dsi_atomic_pre_enable()
just after rzg2l_mipi_dsi_set_display_timing() call.
ret = rzg2l_mipi_dsi_start_video(dsi);
if (ret < 0)
goto err_stop_clock;
@@ -1074,6 +1078,7 @@ static void
rzg2l_mipi_dsi_atomic_post_disable(struct drm_bridge *bridge, {
struct rzg2l_mipi_dsi *dsi = bridge_to_rzg2l_mipi_dsi(bridge);
+ reset_control_assert(dsi->rstc);
rzg2l_mipi_dsii_stop(dsi);
rzg2l_mipi_dsi_stop() is writing DSIDPHYCTRL0 reg via dphy_exit().
I think the right order should be:
rzg2l_mipi_dsii_stop(dsi);
reset_control_assert(dsi->rstc);
.atomic_pre_enable()
dsi_start()
reset_deassert()-->G
.atomic_post_disbale()
Just opposite of atomic_pre_enable()
reset_assert()-->G
dsi_stop()
You're right, please ignore me on this part.
I missed that the hardware manual only requires TXSETR/ULPSSETR/DSISETR/CLSTPTSETR/LPTRNSTSETR to be written before deasserting CMN_RSTB.
The placement of set_display_timing() in atomic_enable() is correct.
Meanwhile I've tested the series on RZ/G3E EVK.
Tested-by: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>
Kind Regards,
Tommaso
Cheers,
Biju