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Message-ID: <267d49d8-a73a-0317-cb50-0f63f0ced049@baylibre.com>
Date: Tue, 21 Apr 2020 17:55:38 +0200
From: Neil Armstrong <narmstrong@...libre.com>
To: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
dri-devel@...ts.freedesktop.org,
Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
David Airlie <airlied@...ux.ie>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, devicetree@...r.kernel.org,
Rob Herring <robh+dt@...nel.org>,
Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH v3 1/2] DRM: ARC: add HDMI 2.0 TX encoder support
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@...nborg.org>
>> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.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@...opsys.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@...gutronix.de>
>> L: netdev@...r.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@...opsys.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@...opsys.com>");
>> --
>> 2.21.1
>>
>
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