From 215be713d05dfb037818b53c402753934e881d76 Mon Sep 17 00:00:00 2001
From: Samuel Holland <samuel@sholland.org>
Date: Tue, 11 Feb 2020 01:28:58 -0600
Subject: drm/sun4i: dsi: Remove incorrect use of runtime PM
Git-commit: 215be713d05dfb037818b53c402753934e881d76
Patch-mainline: v5.7-rc1
References: bsc#1113956
The driver currently uses runtime PM to perform some of the module
initialization and cleanup. This has three problems:
1) There is no Kconfig dependency on CONFIG_PM, so if runtime PM is
disabled, the driver will not work at all, since the module will
never be initialized.
2) The driver does not ensure that the device is suspended when
sun6i_dsi_probe() fails or when sun6i_dsi_remove() is called. It
simply disables runtime PM. From the docs of pm_runtime_disable():
The device can be either active or suspended after its runtime PM
has been disabled.
And indeed, the device will likely still be active if sun6i_dsi_probe
fails. For example, if the panel driver is not yet loaded, we have
the following sequence:
sun6i_dsi_probe()
pm_runtime_enable()
mipi_dsi_host_register()
of_mipi_dsi_device_add(child)
...device_add()...
__device_attach()
pm_runtime_get_sync(dev->parent) -> Causes resume
bus_for_each_drv()
__device_attach_driver() -> No match for panel
pm_runtime_put(dev->parent) -> Async idle request
component_add()
__component_add()
try_to_bring_up_masters()
try_to_bring_up_master()
sun4i_drv_bind()
component_bind_all()
component_bind()
sun6i_dsi_bind() -> Fails with -EPROBE_DEFER
mipi_dsi_host_unregister()
pm_runtime_disable()
__pm_runtime_disable()
__pm_runtime_barrier() -> Idle request is still pending
cancel_work_sync() -> DSI host is *not* suspended!
Since the device is not suspended, the clock and regulator are never
disabled. The imbalance causes a WARN at devres free time.
3) The driver relies on being suspended when sun6i_dsi_encoder_enable()
is called. The resume callback has a comment that says:
Some part of it can only be done once we get a number of
lanes, see sun6i_dsi_inst_init
And then part of the resume callback only runs if dsi->device is not
NULL (that is, if sun6i_dsi_attach() has been called). However, as
the above call graph shows, the resume callback is guaranteed to be
called before sun6i_dsi_attach(); it is called before child devices
get their drivers attached.
Therefore, part of the controller initialization will only run if the
device is suspended between the calls to mipi_dsi_host_register() and
component_add() (which ends up calling sun6i_dsi_encoder_enable()).
Again, as shown by the above call graph, this is not the case. It
appears that the controller happens to work because it is still
initialized by the bootloader.
Because the connector is hardcoded to always be connected, the
device's runtime PM reference is not dropped until system suspend,
when sun4i_drv_drm_sys_suspend() ends up calling
sun6i_dsi_encoder_disable(). However, that is done as a system sleep
PM hook, and at that point the system PM core has already taken
another runtime PM reference, so sun6i_dsi_runtime_suspend() is
not called. Likewise, by the time the PM core releases its reference,
sun4i_drv_drm_sys_resume() has already re-enabled the encoder.
So after system suspend and resume, we have *still never called*
sun6i_dsi_inst_init(), and now that the rest of the display pipeline
has been reset, the DSI host is unable to communicate with the panel,
causing VBLANK timeouts.
Fix all of these issues by inlining the runtime PM hooks into the
encoder enable/disable functions, which are guaranteed to run after a
panel is attached. This allows sun6i_dsi_inst_init() to be called
unconditionally. Furthermore, this causes the hardware to be turned off
during system suspend and reinitialized on resume, which was not
happening before.
Fixes: 133add5b5ad4 ("drm/sun4i: Add Allwinner A31 MIPI-DSI controller support")
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200211072858.30784-4-samuel@sholland.org
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
[ ptesarik: Remove enable/disable regulator, because SLE15-SP1 does not
contain upstream commit 1c056ad87117c47a02b73df63555788b751968c4. ]
Signed-off-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 72 ++++++++-------------------------
1 file changed, 19 insertions(+), 53 deletions(-)
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -10,7 +10,6 @@
#include <linux/component.h>
#include <linux/crc-ccitt.h>
#include <linux/of_address.h>
-#include <linux/pm_runtime.h>
#include <linux/regmap.h>
#include <linux/reset.h>
#include <linux/slab.h>
@@ -623,7 +622,23 @@ static void sun6i_dsi_encoder_enable(str
DRM_DEBUG_DRIVER("Enabling DSI output\n");
- pm_runtime_get_sync(dsi->dev);
+ reset_control_deassert(dsi->reset);
+ clk_prepare_enable(dsi->mod_clk);
+
+ /*
+ * Enable the DSI block.
+ */
+ regmap_write(dsi->regs, SUN6I_DSI_CTL_REG, SUN6I_DSI_CTL_EN);
+
+ regmap_write(dsi->regs, SUN6I_DSI_BASIC_CTL0_REG,
+ SUN6I_DSI_BASIC_CTL0_ECC_EN | SUN6I_DSI_BASIC_CTL0_CRC_EN);
+
+ regmap_write(dsi->regs, SUN6I_DSI_TRANS_START_REG, 10);
+ regmap_write(dsi->regs, SUN6I_DSI_TRANS_ZERO_REG, 0);
+
+ sun6i_dsi_inst_init(dsi, dsi->device);
+
+ regmap_write(dsi->regs, SUN6I_DSI_DEBUG_DATA_REG, 0xff);
delay = sun6i_dsi_get_video_start_delay(dsi, mode);
regmap_write(dsi->regs, SUN6I_DSI_BASIC_CTL1_REG,
@@ -682,7 +702,8 @@ static void sun6i_dsi_encoder_disable(st
sun6i_dphy_power_off(dsi->dphy);
sun6i_dphy_exit(dsi->dphy);
- pm_runtime_put(dsi->dev);
+ clk_disable_unprepare(dsi->mod_clk);
+ reset_control_assert(dsi->reset);
}
static int sun6i_dsi_get_modes(struct drm_connector *connector)
@@ -1036,8 +1058,6 @@ static int sun6i_dsi_probe(struct platfo
goto err_unprotect_clk;
}
- pm_runtime_enable(dev);
-
ret = mipi_dsi_host_register(&dsi->host);
if (ret) {
dev_err(dev, "Couldn't register MIPI-DSI host\n");
@@ -1055,7 +1075,6 @@ static int sun6i_dsi_probe(struct platfo
err_remove_dsi_host:
mipi_dsi_host_unregister(&dsi->host);
err_remove_phy:
- pm_runtime_disable(dev);
sun6i_dphy_remove(dsi);
err_unprotect_clk:
return ret;
@@ -1068,57 +1087,11 @@ static int sun6i_dsi_remove(struct platf
component_del(&pdev->dev, &sun6i_dsi_ops);
mipi_dsi_host_unregister(&dsi->host);
- pm_runtime_disable(dev);
sun6i_dphy_remove(dsi);
return 0;
}
-static int __maybe_unused sun6i_dsi_runtime_resume(struct device *dev)
-{
- struct sun6i_dsi *dsi = dev_get_drvdata(dev);
-
- reset_control_deassert(dsi->reset);
- clk_prepare_enable(dsi->mod_clk);
-
- /*
- * Enable the DSI block.
- *
- * Some part of it can only be done once we get a number of
- * lanes, see sun6i_dsi_inst_init
- */
- regmap_write(dsi->regs, SUN6I_DSI_CTL_REG, SUN6I_DSI_CTL_EN);
-
- regmap_write(dsi->regs, SUN6I_DSI_BASIC_CTL0_REG,
- SUN6I_DSI_BASIC_CTL0_ECC_EN | SUN6I_DSI_BASIC_CTL0_CRC_EN);
-
- regmap_write(dsi->regs, SUN6I_DSI_TRANS_START_REG, 10);
- regmap_write(dsi->regs, SUN6I_DSI_TRANS_ZERO_REG, 0);
-
- if (dsi->device)
- sun6i_dsi_inst_init(dsi, dsi->device);
-
- regmap_write(dsi->regs, SUN6I_DSI_DEBUG_DATA_REG, 0xff);
-
- return 0;
-}
-
-static int __maybe_unused sun6i_dsi_runtime_suspend(struct device *dev)
-{
- struct sun6i_dsi *dsi = dev_get_drvdata(dev);
-
- clk_disable_unprepare(dsi->mod_clk);
- reset_control_assert(dsi->reset);
-
- return 0;
-}
-
-static const struct dev_pm_ops sun6i_dsi_pm_ops = {
- SET_RUNTIME_PM_OPS(sun6i_dsi_runtime_suspend,
- sun6i_dsi_runtime_resume,
- NULL)
-};
-
static const struct of_device_id sun6i_dsi_of_table[] = {
{ .compatible = "allwinner,sun6i-a31-mipi-dsi" },
{ }
@@ -1131,7 +1104,6 @@ static struct platform_driver sun6i_dsi_
.driver = {
.name = "sun6i-mipi-dsi",
.of_match_table = sun6i_dsi_of_table,
- .pm = &sun6i_dsi_pm_ops,
},
};
module_platform_driver(sun6i_dsi_platform_driver);