On Thu, May 19, 2022 at 09:26:59AM -0700, Guillaume Ranquet wrote:

On Thu, 12 May 2022 09:44, Maxime Ripard [off-list ref] wrote:

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Hi,

On Wed, May 11, 2022 at 05:59:13AM -0700, Guillaume Ranquet wrote:

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+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_crtc.h>
+#include <drm/dp/drm_dp_helper.h>
+#include <drm/drm_edid.h>
+#include <drm/drm_of.h>
+#include <drm/drm_panel.h>
+#include <drm/drm_print.h>
+#include <drm/drm_probe_helper.h>
+#include <linux/arm-smccc.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/phy/phy.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+#include <sound/hdmi-codec.h>
+#include <video/videomode.h>
+
+#include "mtk_dp_reg.h"
+
+#define MTK_DP_AUX_WAIT_REPLY_COUNT 20
+#define MTK_DP_CHECK_SINK_CAP_TIMEOUT_COUNT 3
+
+//TODO: platform/device data or dts?

DTS :)

It's probably going to be a platform_data struct for v10...
If I have time, I'll change it to a dts property for v10.

I can't really imagine a case where we would need platform_data
nowadays. If you have a device tree, then it should be part of the
binding.

What issue would you like to address by using a platform_data?

Ok, I'll migrate to dt then. I didn't realize platform_data were depreciated.

Angelo wants the MAX_LINRATE and MAX_LANES defines to be configurable.
I imagined platform_data would be more appropriate as (per my understanding) the
limitation is associated with a specific SoC.

The entire device tree is nothing but a collection of data associated to
a specific SoC though :)

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+static struct edid *mtk_dp_get_edid(struct drm_bridge *bridge,
+				    struct drm_connector *connector)
+{
+	struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
+	bool enabled = mtk_dp->enabled;
+	struct edid *new_edid = NULL;
+
+	if (!enabled)
+		drm_bridge_chain_pre_enable(bridge);
+
+	drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D0);
+	usleep_range(2000, 5000);
+
+	if (mtk_dp_plug_state(mtk_dp))
+		new_edid = drm_get_edid(connector, &mtk_dp->aux.ddc);
+
+	if (!enabled)
+		drm_bridge_chain_post_disable(bridge);

Are you sure we can't get a mode set while get_edid is called?

If we can, then you could end up disabling the device while it's being
powered on.

I'm a bit unsure, I need to spend more time in the drm stack to make sure.
I'll get back to you when I have a definitive answer.

So, it looks like it's ok.

get_edid is your implementation of get_modes, which is called by
drm_helper_probe_single_connector_modes

https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_probe_helper.c#L416

This is the standard implemantion of fill_modes, which is called
whenever the get_connector ioctl is called (or similar paths, like
drm_client_modeset_probe)

drm_helper_probe_single_connector_modes is under the assumption that the
mode_config.mutex is held though, and that the big lock. So it should be
serialized there.

Just for future proofing though, it would be better to use refcounting
there. Would runtime_pm work for you there?

Thx for looking into this for me.
Not sure runtime_pm works here as it would only refcount if compiled
with CONFIG_PM?

It should be enabled in most configurations these days, and you can
always depend on it in your Kconfig option.

I'd rather use the enabled field as a refcounter instead of a boolean.

It's a bit more ad-hoc, but that would work too. Make sure to use a lock
or atomic operations though

Maxime