On Wed, Apr 17, 2024 at 08:11:35AM +0530, Dharma Balasubiramani wrote:
> Add a new LVDS controller driver for sam9x7 which does the following:
> - Prepares and enables the LVDS Peripheral clock
> - Defines its connector type as DRM_MODE_CONNECTOR_LVDS and adds itself
> to the global bridge list.
> - Identifies its output endpoint as panel and adds it to the encoder
> display pipeline
> - Enables the LVDS serializer
>
> Signed-off-by: Manikandan Muralidharan <manikandan.m@xxxxxxxxxxxxx>
> Signed-off-by: Dharma Balasubiramani <dharma.b@xxxxxxxxxxxxx>
> ---
> Changelog
> v5 -> v6
> - No Changes.
> v4 -> v5
> - Drop the unused variable 'format'.
> - Use DRM wrapper for dev_err() to maintain uniformity.
> - return -ENODEV instead of -EINVAL to maintain consistency with other DRM
> bridge drivers.
> v3 -> v4
> - No changes.
> v2 ->v3
> - Correct Typo error "serializer".
> - Consolidate get() and prepare() functions and use devm_clk_get_prepared().
> - Remove unused variable 'ret' in probe().
> - Use devm_pm_runtime_enable() and drop the mchp_lvds_remove().
> v1 -> v2
> - Drop 'res' variable and combine two lines into one.
> - Handle deferred probe properly, use dev_err_probe().
> - Don't print anything on deferred probe. Dropped print.
> - Remove the MODULE_ALIAS and add MODULE_DEVICE_TABLE().
> - symbol 'mchp_lvds_driver' was not declared. It should be static.
> ---
> drivers/gpu/drm/bridge/Kconfig | 7 +
> drivers/gpu/drm/bridge/Makefile | 1 +
> drivers/gpu/drm/bridge/microchip-lvds.c | 228 ++++++++++++++++++++++++
> 3 files changed, 236 insertions(+)
> create mode 100644 drivers/gpu/drm/bridge/microchip-lvds.c
>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index efd996f6c138..889098e2d65f 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -190,6 +190,13 @@ config DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW
> to DP++. This is used with the i.MX6 imx-ldb
> driver. You are likely to say N here.
>
> +config DRM_MICROCHIP_LVDS_SERIALIZER
> + tristate "Microchip LVDS serializer support"
> + depends on OF
> + depends on DRM_ATMEL_HLCDC
> + help
> + Support for Microchip's LVDS serializer.
> +
> config DRM_NWL_MIPI_DSI
> tristate "Northwest Logic MIPI DSI Host controller"
> depends on DRM
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 017b5832733b..7df87b582dca 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -13,6 +13,7 @@ obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
> obj-$(CONFIG_DRM_LONTIUM_LT9611UXC) += lontium-lt9611uxc.o
> obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
> obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
> +obj-$(CONFIG_DRM_MICROCHIP_LVDS_SERIALIZER) += microchip-lvds.o
> obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
> obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
> obj-$(CONFIG_DRM_PARADE_PS8640) += parade-ps8640.o
> diff --git a/drivers/gpu/drm/bridge/microchip-lvds.c b/drivers/gpu/drm/bridge/microchip-lvds.c
> new file mode 100644
> index 000000000000..149704f498a6
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/microchip-lvds.c
> @@ -0,0 +1,228 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2023 Microchip Technology Inc. and its subsidiaries
> + *
> + * Author: Manikandan Muralidharan <manikandan.m@xxxxxxxxxxxxx>
> + * Author: Dharma Balasubiramani <dharma.b@xxxxxxxxxxxxx>
> + *
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/component.h>
> +#include <linux/delay.h>
> +#include <linux/jiffies.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/of_graph.h>
> +#include <linux/pinctrl/devinfo.h>
> +#include <linux/phy/phy.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_of.h>
> +#include <drm/drm_panel.h>
> +#include <drm/drm_print.h>
> +#include <drm/drm_probe_helper.h>
> +#include <drm/drm_simple_kms_helper.h>
> +
> +#define LVDS_POLL_TIMEOUT_MS 1000
> +
> +/* LVDSC register offsets */
> +#define LVDSC_CR 0x00
> +#define LVDSC_CFGR 0x04
> +#define LVDSC_SR 0x0C
> +#define LVDSC_WPMR 0xE4
> +
> +/* Bitfields in LVDSC_CR (Control Register) */
> +#define LVDSC_CR_SER_EN BIT(0)
> +
> +/* Bitfields in LVDSC_CFGR (Configuration Register) */
> +#define LVDSC_CFGR_PIXSIZE_24BITS 0
> +#define LVDSC_CFGR_DEN_POL_HIGH 0
> +#define LVDSC_CFGR_DC_UNBALANCED 0
> +#define LVDSC_CFGR_MAPPING_JEIDA BIT(6)
> +
> +/*Bitfields in LVDSC_SR */
> +#define LVDSC_SR_CS BIT(0)
> +
> +/* Bitfields in LVDSC_WPMR (Write Protection Mode Register) */
> +#define LVDSC_WPMR_WPKEY_MASK GENMASK(31, 8)
> +#define LVDSC_WPMR_WPKEY_PSSWD 0x4C5644
> +
> +struct mchp_lvds {
> + struct device *dev;
> + void __iomem *regs;
> + struct clk *pclk;
> + struct drm_panel *panel;
> + struct drm_bridge bridge;
> + struct drm_bridge *panel_bridge;
> +};
> +
> +static inline struct mchp_lvds *bridge_to_lvds(struct drm_bridge *bridge)
> +{
> + return container_of(bridge, struct mchp_lvds, bridge);
> +}
> +
> +static inline u32 lvds_readl(struct mchp_lvds *lvds, u32 offset)
> +{
> + return readl_relaxed(lvds->regs + offset);
> +}
> +
> +static inline void lvds_writel(struct mchp_lvds *lvds, u32 offset, u32 val)
> +{
> + writel_relaxed(val, lvds->regs + offset);
> +}
> +
> +static void lvds_serialiser_on(struct mchp_lvds *lvds)
> +{
> + unsigned long timeout = jiffies + msecs_to_jiffies(LVDS_POLL_TIMEOUT_MS);
> +
> + /* The LVDSC registers can only be written if WPEN is cleared */
> + lvds_writel(lvds, LVDSC_WPMR, (LVDSC_WPMR_WPKEY_PSSWD &
> + LVDSC_WPMR_WPKEY_MASK));
> +
> + /* Wait for the status of configuration registers to be changed */
> + while (lvds_readl(lvds, LVDSC_SR) & LVDSC_SR_CS) {
> + if (time_after(jiffies, timeout)) {
> + DRM_DEV_ERROR(lvds->dev, "%s: timeout error\n",
> + __func__);
> + return;
> + }
> + usleep_range(1000, 2000);
> + }
> +
> + /* Configure the LVDSC */
> + lvds_writel(lvds, LVDSC_CFGR, (LVDSC_CFGR_MAPPING_JEIDA |
> + LVDSC_CFGR_DC_UNBALANCED |
> + LVDSC_CFGR_DEN_POL_HIGH |
> + LVDSC_CFGR_PIXSIZE_24BITS));
> +
> + /* Enable the LVDS serializer */
> + lvds_writel(lvds, LVDSC_CR, LVDSC_CR_SER_EN);
> +}
> +
> +static int mchp_lvds_attach(struct drm_bridge *bridge,
> + enum drm_bridge_attach_flags flags)
> +{
> + struct mchp_lvds *lvds = bridge_to_lvds(bridge);
> +
> + bridge->encoder->encoder_type = DRM_MODE_ENCODER_LVDS;
Why do you need to touch encoder_type here? It's not your bridge's
responsibility.
> +
> + return drm_bridge_attach(bridge->encoder, lvds->panel_bridge,
> + bridge, flags);
> +}
> +
> +static void mchp_lvds_enable(struct drm_bridge *bridge)
> +{
> + struct mchp_lvds *lvds = bridge_to_lvds(bridge);
> + int ret;
> +
> + ret = clk_enable(lvds->pclk);
> + if (ret < 0) {
> + DRM_DEV_ERROR(lvds->dev, "failed to enable lvds pclk %d\n", ret);
> + return;
> + }
> +
> + ret = pm_runtime_get_sync(lvds->dev);
> + if (ret < 0) {
> + DRM_DEV_ERROR(lvds->dev, "failed to get pm runtime: %d\n", ret);
> + clk_disable(lvds->pclk);
This can result in unbalanced clk_disable(), if pm_runtime_get_sync()
fails. This function calls clk_disable(), but the framework has no way
to know that .enable() was not successful and calls .disable(), which
also calls clk_disable().
Please consider turning pclk into pm_clk so that its state is managed
automatically (or at least moving clk_enable/disable into pm_ops).
> + return;
> + }
> +
> + lvds_serialiser_on(lvds);
> +}
> +
> +static void mchp_lvds_disable(struct drm_bridge *bridge)
> +{
> + struct mchp_lvds *lvds = bridge_to_lvds(bridge);
> +
> + pm_runtime_put(lvds->dev);
> + clk_disable(lvds->pclk);
> +}
> +
> +static const struct drm_bridge_funcs mchp_lvds_bridge_funcs = {
> + .attach = mchp_lvds_attach,
> + .enable = mchp_lvds_enable,
> + .disable = mchp_lvds_disable,
> +};
> +
> +static int mchp_lvds_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct mchp_lvds *lvds;
> + struct device_node *port;
> +
> + if (!dev->of_node)
> + return -ENODEV;
> +
> + lvds = devm_kzalloc(&pdev->dev, sizeof(*lvds), GFP_KERNEL);
> + if (!lvds)
> + return -ENOMEM;
> +
> + lvds->dev = dev;
> +
> + lvds->regs = devm_ioremap_resource(lvds->dev,
> + platform_get_resource(pdev, IORESOURCE_MEM, 0));
> + if (IS_ERR(lvds->regs))
> + return PTR_ERR(lvds->regs);
> +
> + lvds->pclk = devm_clk_get_prepared(lvds->dev, "pclk");
Why do you need _prepared version?
> + if (IS_ERR(lvds->pclk))
> + return dev_err_probe(lvds->dev, PTR_ERR(lvds->pclk),
> + "could not get pclk_lvds prepared\n");
> +
> + port = of_graph_get_remote_node(dev->of_node, 1, 0);
> + if (!port) {
> + DRM_DEV_ERROR(dev,
> + "can't find port point, please init lvds panel port!\n");
> + return -ENODEV;
> + }
> +
> + lvds->panel = of_drm_find_panel(port);
> + of_node_put(port);
> +
> + if (IS_ERR(lvds->panel))
> + return -EPROBE_DEFER;
> +
> + lvds->panel_bridge = devm_drm_panel_bridge_add(dev, lvds->panel);
Please use instead:
devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
> +
> + if (IS_ERR(lvds->panel_bridge))
> + return PTR_ERR(lvds->panel_bridge);
> +
> + lvds->bridge.of_node = dev->of_node;
> + lvds->bridge.type = DRM_MODE_CONNECTOR_LVDS;
> + lvds->bridge.funcs = &mchp_lvds_bridge_funcs;
> +
> + dev_set_drvdata(dev, lvds);
> + devm_pm_runtime_enable(dev);
Error check is missing.
> +
> + drm_bridge_add(&lvds->bridge);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id mchp_lvds_dt_ids[] = {
> + {
> + .compatible = "microchip,sam9x75-lvds",
> + },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, mchp_lvds_dt_ids);
> +
> +static struct platform_driver mchp_lvds_driver = {
> + .probe = mchp_lvds_probe,
> + .driver = {
> + .name = "microchip-lvds",
> + .of_match_table = mchp_lvds_dt_ids,
> + },
> +};
> +module_platform_driver(mchp_lvds_driver);
> +
> +MODULE_AUTHOR("Manikandan Muralidharan <manikandan.m@xxxxxxxxxxxxx>");
> +MODULE_AUTHOR("Dharma Balasubiramani <dharma.b@xxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Low Voltage Differential Signaling Controller Driver");
> +MODULE_LICENSE("GPL");
> --
> 2.25.1
>
--
With best wishes
Dmitry
