Date: Mon, 26 Feb 2024 04:00:52 +0000
From: <Dharma.B@...rochip.com>
To: <andrzej.hajda@...el.com>, <neil.armstrong@...aro.org>,
	<rfoss@...nel.org>, <Laurent.pinchart@...asonboard.com>, <jonas@...boo.se>,
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	<dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<Hari.PrasathGE@...rochip.com>, <akpm@...ux-foundation.org>, <deller@....de>
Subject: Re: [PATCH v4 2/4] drm/bridge: add lvds controller support for sam9x7


Hi Folks,

Your feedback is valuable, and I'm eager to address any concerns or make
improvements as needed. Thank you for your consideration.

On 09/02/24 8:37 pm, Dharma B - I70843 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@...rochip.com>
> Signed-off-by: Dharma Balasubiramani <dharma.b@...rochip.com>
> ---
> Changelog
> 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 3e6a4e2044c0..74ca0edb4e0d 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -173,6 +173,13 @@ 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 2b892b7ed59e..e3804e93d324 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -11,6 +11,7 @@ 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..d3fd9d722e36
> --- /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@...rochip.com>
> + * Author: Dharma Balasubiramani <dharma.b@...rochip.com>
> + *
> + */
> +
> +#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;
> +	int format; /* vesa or jeida format */
> +	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)) {
> +			dev_err(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;
> +
> +	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);
> +		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");
> +	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 -EINVAL;
> +	}
> +
> +	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);
> +
> +	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);
> +
> +	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@...rochip.com>");
> +MODULE_AUTHOR("Dharma Balasubiramani <dharma.b@...rochip.com>");
> +MODULE_DESCRIPTION("Low Voltage Differential Signaling Controller Driver");
> +MODULE_LICENSE("GPL");

-- 
With Best Regards,
Dharma B.

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