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Subject: Re: [PATCH v3 1/2] DRM: ARC: add HDMI 2.0 TX encoder support
To:     Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>,
        dri-devel@lists.freedesktop.org,
        Alexey Brodkin <Alexey.Brodkin@synopsys.com>,
        linux-snps-arc@lists.infradead.org, linux-kernel@vger.kernel.org,
        David Airlie <airlied@linux.ie>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>, devicetree@vger.kernel.org,
        Rob Herring <robh+dt@kernel.org>,
        Sam Ravnborg <sam@ravnborg.org>
References: <20200414232929.22788-1-Eugeniy.Paltsev@synopsys.com>
 <20200414232929.22788-2-Eugeniy.Paltsev@synopsys.com>
 <20200415173320.GG3456981@phenom.ffwll.local>
From:   Neil Armstrong <narmstrong@baylibre.com>
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Organization: Baylibre
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Date:   Tue, 21 Apr 2020 17:55:38 +0200
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On 15/04/2020 19:33, Daniel Vetter wrote:
> On Wed, Apr 15, 2020 at 02:29:28AM +0300, Eugeniy Paltsev wrote:
>> The Synopsys ARC SoCs (like HSDK4xD) include on-chip DesignWare HDMI
>> encoders. Support them with a platform driver to provide platform glue
>> data to the dw-hdmi driver.
>>
>> Acked-by: Sam Ravnborg <sam@ravnborg.org>
>> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
>> ---
>>  MAINTAINERS                       |   6 ++
>>  drivers/gpu/drm/Makefile          |   2 +-
>>  drivers/gpu/drm/arc/Kconfig       |   7 ++
>>  drivers/gpu/drm/arc/Makefile      |   1 +
>>  drivers/gpu/drm/arc/arc-dw-hdmi.c | 116 ++++++++++++++++++++++++++++++
>>  5 files changed, 131 insertions(+), 1 deletion(-)
>>  create mode 100644 drivers/gpu/drm/arc/arc-dw-hdmi.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index a6fbdf354d34..2aaed1190370 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -1258,6 +1258,12 @@ S:	Supported
>>  F:	drivers/gpu/drm/arc/
>>  F:	Documentation/devicetree/bindings/display/snps,arcpgu.txt
>>  
>> +ARC DW HDMI DRIVER
>> +M:	Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
>> +S:	Supported
>> +F:	drivers/gpu/drm/arc/arc-dw-hdmi.c
>> +F:	Documentation/devicetree/bindings/display/bridge/snps,arc-dw-hdmi.yaml
>> +
>>  ARCNET NETWORK LAYER
>>  M:	Michael Grzeschik <m.grzeschik@pengutronix.de>
>>  L:	netdev@vger.kernel.org
>> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
>> index 6493088a0fdd..5b0bcf7f45cd 100644
>> --- a/drivers/gpu/drm/Makefile
>> +++ b/drivers/gpu/drm/Makefile
>> @@ -109,7 +109,7 @@ obj-y			+= panel/
>>  obj-y			+= bridge/
>>  obj-$(CONFIG_DRM_FSL_DCU) += fsl-dcu/
>>  obj-$(CONFIG_DRM_ETNAVIV) += etnaviv/
>> -obj-$(CONFIG_DRM_ARCPGU)+= arc/
>> +obj-y			+= arc/
>>  obj-y			+= hisilicon/
>>  obj-$(CONFIG_DRM_ZTE)	+= zte/
>>  obj-$(CONFIG_DRM_MXSFB)	+= mxsfb/
>> diff --git a/drivers/gpu/drm/arc/Kconfig b/drivers/gpu/drm/arc/Kconfig
>> index e8f3d63e0b91..baec9d2a4fba 100644
>> --- a/drivers/gpu/drm/arc/Kconfig
>> +++ b/drivers/gpu/drm/arc/Kconfig
>> @@ -8,3 +8,10 @@ config DRM_ARCPGU
>>  	  Choose this option if you have an ARC PGU controller.
>>  
>>  	  If M is selected the module will be called arcpgu.
>> +
>> +config DRM_ARC_DW_HDMI
>> +	tristate "ARC DW HDMI"
>> +	depends on DRM && OF
>> +	select DRM_DW_HDMI
>> +	help
>> +	  Synopsys DW HDMI driver for various ARC development boards
>> diff --git a/drivers/gpu/drm/arc/Makefile b/drivers/gpu/drm/arc/Makefile
>> index c7028b7427b3..7a156d8c2c3c 100644
>> --- a/drivers/gpu/drm/arc/Makefile
>> +++ b/drivers/gpu/drm/arc/Makefile
>> @@ -1,3 +1,4 @@
>>  # SPDX-License-Identifier: GPL-2.0-only
>>  arcpgu-y := arcpgu_crtc.o arcpgu_hdmi.o arcpgu_sim.o arcpgu_drv.o
>>  obj-$(CONFIG_DRM_ARCPGU) += arcpgu.o
>> +obj-$(CONFIG_DRM_ARC_DW_HDMI) += arc-dw-hdmi.o
>> diff --git a/drivers/gpu/drm/arc/arc-dw-hdmi.c b/drivers/gpu/drm/arc/arc-dw-hdmi.c
>> new file mode 100644
>> index 000000000000..46a6ee09b302
>> --- /dev/null
>> +++ b/drivers/gpu/drm/arc/arc-dw-hdmi.c
>> @@ -0,0 +1,116 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +//
>> +// Synopsys DW HDMI driver for various ARC development boards
>> +//
>> +// Copyright (C) 2020 Synopsys
>> +// Author: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
>> +
>> +#include <linux/component.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <drm/bridge/dw_hdmi.h>
>> +#include <drm/drm_crtc_helper.h>
>> +#include <drm/drm_edid.h>
>> +#include <drm/drm_encoder_slave.h>
>> +#include <drm/drm_of.h>
>> +
>> +static const struct dw_hdmi_mpll_config snps_hdmi_mpll_cfg[] = {
>> +	{
>> +		27000000, {
>> +			{ 0x00B3, 0x0000 },
>> +			{ 0x00B3, 0x0000 },
>> +			{ 0x00B3, 0x0000 }
>> +		},
>> +	}, {
>> +		74250000, {
>> +			{ 0x0072, 0x0001},
>> +			{ 0x0072, 0x0001},
>> +			{ 0x0072, 0x0001}
>> +		},
>> +	}, {
>> +		148500000, {
>> +			{ 0x0051, 0x0002},
>> +			{ 0x0051, 0x0002},
>> +			{ 0x0051, 0x0002}
>> +		},
>> +	}, {
>> +		~0UL, {
>> +			{ 0x00B3, 0x0000 },
>> +			{ 0x00B3, 0x0000 },
>> +			{ 0x00B3, 0x0000 },
>> +		},
>> +	}
>> +};
>> +
>> +static const struct dw_hdmi_curr_ctrl snps_hdmi_cur_ctr[] = {
>> +	/* pixelclk    bpp8    bpp10   bpp12 */
>> +	{ 27000000,  { 0x0000, 0x0000, 0x0000 }, },
>> +	{ 74250000,  { 0x0008, 0x0008, 0x0008 }, },
>> +	{ 148500000, { 0x001b, 0x001b, 0x001b }, },
>> +	{ ~0UL,      { 0x0000, 0x0000, 0x0000 }, }
>> +};
>> +
>> +
>> +static const struct dw_hdmi_phy_config snps_hdmi_phy_config[] = {
>> +	/* pixelclk   symbol  term    vlev */
>> +	{ 27000000,   0x8009, 0x0004, 0x0232},
>> +	{ 74250000,   0x8009, 0x0004, 0x0232},
>> +	{ 148500000,  0x8009, 0x0004, 0x0232},
>> +	{ ~0UL,       0x8009, 0x0004, 0x0232}
>> +};
>> +
>> +static struct dw_hdmi_plat_data snps_dw_hdmi_drv_data = {
>> +	.mpll_cfg   = snps_hdmi_mpll_cfg,
>> +	.cur_ctr    = snps_hdmi_cur_ctr,
>> +	.phy_config = snps_hdmi_phy_config,
>> +};
>> +
>> +static const struct of_device_id snps_dw_hdmi_dt_ids[] = {
>> +	{ .compatible = "snps,arc-dw-hdmi-hsdk", .data = &snps_dw_hdmi_drv_data },
>> +	{ /* sentinel */ }
>> +};
>> +MODULE_DEVICE_TABLE(of, snps_dw_hdmi_dt_ids);
>> +
>> +static int snps_dw_hdmi_probe(struct platform_device *pdev)
>> +{
>> +	const struct dw_hdmi_plat_data *plat_data;
>> +	const struct of_device_id *match;
>> +	struct dw_hdmi *hdmi;
>> +
>> +	if (!pdev->dev.of_node)
>> +		return -ENODEV;
>> +
>> +	match = of_match_node(snps_dw_hdmi_dt_ids, pdev->dev.of_node);
>> +	plat_data = match->data;
>> +
>> +	hdmi = dw_hdmi_probe(pdev, plat_data);
> 
> So this is kinda not how bridge drivers are supposed to be done nowadays,
> direct calling into the driver was the old way, and dw-hdmi still works
> like that. Modern way is roughly
> - bridge drivers bind automatically to any bridge they support
> - bridge drivers publish a bridge with drm_bridge_add()
> - the driver using the bridge fishes out with dt magic using
>   of_drm_find_bridge() or another of the related of_ functions

dw-hdmi is an IP, with some platform specific code and arrays to make it work
on very different systems, thus we can't use this scheme everywhere....

Some platforms (like r-car) uses the "right" model because the IP is integrated
as-is with the default PHY and as an independent IP on the system.

It's definitely not the case on Rockchip/Amlogic/Allwinner systems,
and even worse on Amlogic system having a glue on top of the IP, and a
custom PHY instead of the Synopsys PHY.

Thus it would be great this would be the case on a Synopsys SoC... but like
other platforms they have platform specific parameters.

All this has been discussed and reviewed a few years ago, I would
personally prefer "fishing out a bridge using dt magic" instead having
1k glue code around the IP.

Neil

> 
> I know a bit late, just spotted this because you brought your series here
> up in my arc cleanup series, but can you pls look into adjusting
> accordingly?
> 
> I shouldn't take more than moving this binding here into the dw-hdmi
> driver, and switching arc itself over to the of_drm_find_bridge() call.
> That way we could slowly work to transform old bridge drivers like dw-hdmi
> to the new way, instead of adding more cases that will never get
> converted.
> 
> Other upside is that arc stays a neat&tiny driver :-)
> 
> Thanks, Daniel
> 
>> +	if (IS_ERR(hdmi))
>> +		return PTR_ERR(hdmi);
>> +
>> +	platform_set_drvdata(pdev, hdmi);
>> +
>> +	return 0;
>> +}
>> +
>> +static int snps_dw_hdmi_remove(struct platform_device *pdev)
>> +{
>> +	struct dw_hdmi *hdmi = platform_get_drvdata(pdev);
>> +
>> +	dw_hdmi_remove(hdmi);
>> +
>> +	return 0;
>> +}
>> +
>> +static struct platform_driver snps_dw_hdmi_platform_driver = {
>> +	.probe  = snps_dw_hdmi_probe,
>> +	.remove = snps_dw_hdmi_remove,
>> +	.driver = {
>> +		.name = KBUILD_MODNAME,
>> +		.of_match_table = snps_dw_hdmi_dt_ids,
>> +	},
>> +};
>> +module_platform_driver(snps_dw_hdmi_platform_driver);
>> +
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_DESCRIPTION("ARC specific DW-HDMI driver extension");
>> +MODULE_AUTHOR("Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>");
>> -- 
>> 2.21.1
>>
>