Re: [PATCH v2 6/8] drm/panel: add driver for samsung amb655x

On Tue, 2 Jul 2024 at 12:43, Caleb Connolly [off-list ref] wrote:

On 01/07/2024 22:32, Dmitry Baryshkov wrote:

quoted

On Sun, Jun 30, 2024 at 08:36:29PM GMT, Caleb Connolly wrote:

quoted

This is a 1080x2400 120hz panel used on the OnePlus 8T. It uses DSC but
with many non-standard DCS commands.

The only user of this panel (the OnePlus 8T) has a bug somewhere in the
DSI stack whereby it isn't possible to properly initialize this panel
after a reset. As a result, the reset GPIO is made optional so it can be
left unused on that device.

Signed-off-by: Caleb Connolly <redacted>
---
  MAINTAINERS                                   |   7 +
  drivers/gpu/drm/panel/Kconfig                 |   9 +
  drivers/gpu/drm/panel/Makefile                |   1 +
  drivers/gpu/drm/panel/panel-samsung-amb655x.c | 399 ++++++++++++++++++++++++++
  4 files changed, 416 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 807feae089c4..2b9cfbf92d7a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -7142,8 +7142,15 @@ M:    Robert Chiras <robert.chiras@nxp.com>
  S: Maintained
  F: Documentation/devicetree/bindings/display/panel/raydium,rm67191.yaml
  F: drivers/gpu/drm/panel/panel-raydium-rm67191.c

+DRM DRIVER FOR SAMSUNG AMB655X PANEL
+M:  Caleb Connolly <caleb@postmarketos.org>
+S:  Maintained
+T:  git https://gitlab.freedesktop.org/drm/misc/kernel.git
+F:  Documentation/devicetree/bindings/display/panel/samsung,amb655x.yaml
+F:  drivers/gpu/drm/panel/panel-samsung-amb655x.c
+
  DRM DRIVER FOR SAMSUNG DB7430 PANELS
  M: Linus Walleij <linus.walleij@linaro.org>
  S: Maintained
  T: git https://gitlab.freedesktop.org/drm/misc/kernel.git

diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index bf4eadfe21cb..7203d16ab20a 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig

@@ -590,8 +590,17 @@ config DRM_PANEL_SAMSUNG_S6E88A0_AMS452EF01
     depends on OF
     select DRM_MIPI_DSI
     select VIDEOMODE_HELPERS

+config DRM_PANEL_SAMSUNG_AMB655X
+    tristate "Samsung AMB655X DSI panel"
+    depends on OF
+    depends on DRM_MIPI_DSI
+    depends on BACKLIGHT_CLASS_DEVICE
+    help
+      DRM panel driver for the Samsung AMB655X panel.
+      This panel has a resolution of 1080x2400 @ 60hz or 120Hz.
+
  config DRM_PANEL_SAMSUNG_ATNA33XC20
     tristate "Samsung ATNA33XC20 eDP panel"
     depends on OF
     depends on BACKLIGHT_CLASS_DEVICE

diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
index 051b75b3df7b..be6d500a56a4 100644
--- a/drivers/gpu/drm/panel/Makefile
+++ b/drivers/gpu/drm/panel/Makefile

@@ -58,8 +58,9 @@ obj-$(CONFIG_DRM_PANEL_RAYDIUM_RM67191) += panel-raydium-rm67191.o
  obj-$(CONFIG_DRM_PANEL_RAYDIUM_RM68200) += panel-raydium-rm68200.o
  obj-$(CONFIG_DRM_PANEL_RAYDIUM_RM692E5) += panel-raydium-rm692e5.o
  obj-$(CONFIG_DRM_PANEL_RAYDIUM_RM69380) += panel-raydium-rm69380.o
  obj-$(CONFIG_DRM_PANEL_RONBO_RB070D30) += panel-ronbo-rb070d30.o
+obj-$(CONFIG_DRM_PANEL_SAMSUNG_AMB655X) += panel-samsung-amb655x.o
  obj-$(CONFIG_DRM_PANEL_SAMSUNG_ATNA33XC20) += panel-samsung-atna33xc20.o
  obj-$(CONFIG_DRM_PANEL_SAMSUNG_DB7430) += panel-samsung-db7430.o
  obj-$(CONFIG_DRM_PANEL_SAMSUNG_LD9040) += panel-samsung-ld9040.o
  obj-$(CONFIG_DRM_PANEL_SAMSUNG_S6D16D0) += panel-samsung-s6d16d0.o

quoted

+static int samsung_amb655x_prepare(struct drm_panel *panel)
+{
+    struct samsung_amb655x *ctx = to_samsung_amb655x(panel);
+    struct device *dev = &ctx->dsi->dev;
+    int ret;
+
+    /*
+     * During the first call to prepare, the regulators are already enabled
+     * since they're boot-on. Avoid enabling them twice so we keep the refcounts
+     * balanced.

I see your intent, but I don't think this is fully correct. If the
driver gets rebound, then it will perform one extra disable call. On the
next driver probe / enable / disable / remove cycle the driver will
perform one more, underflowing enable count. I think
regulator_init_complete_work_function should give the phone enough time
to boot the panel.

I do make an extra call to regulator_bulk_enable() in probe(), does that
balance things out?

Hmm, I missed it. But if you have it, why not just have a single
regulator_bulk_enable() in pre_enable() like everybody else does?

quoted

quoted

+     */
+    if (!regulator_is_enabled(ctx->supplies[0].consumer)) {
+            ret = regulator_bulk_enable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
+            if (ret) {
+                    dev_err(dev, "Failed to enable regulators: %d\n", ret);
+                    return ret;
+            }
+    }
+

-- 
With best wishes
Dmitry