Re: [PATCH v8 15/19] drm/mediatek: Add mt8195 Embedded DisplayPort driver

From: Guillaume Ranquet <granquet@baylibre.com>
To: CK Hu <ck.hu@mediatek.com>,
	airlied@linux.ie,  angelogioacchino.delregno@collabora.com,
	chunfeng.yun@mediatek.com,  chunkuang.hu@kernel.org,
	daniel@ffwll.ch, deller@gmx.de,  jitao.shi@mediatek.com,
	kishon@ti.com, maarten.lankhorst@linux.intel.com,
	 matthias.bgg@gmail.com, mripard@kernel.org,
	p.zabel@pengutronix.de,  robh+dt@kernel.org, tzimmermann@suse.de,
	vkoul@kernel.org
Cc: devicetree@vger.kernel.org, linux-fbdev@vger.kernel.org,
	kernel test robot <lkp@intel.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Markus Schneider-Pargmann <msp@baylibre.com>,
	linux-mediatek@lists.infradead.org,
	linux-phy@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v8 15/19] drm/mediatek: Add mt8195 Embedded DisplayPort driver
Date: Fri, 25 Feb 2022 05:04:46 -0800	[thread overview]
Message-ID: <CABnWg9tv5rgvLgc59PhqCFtPNL+gAVQ-LauAFG=7zuW_yV=PUA@mail.gmail.com> (raw)
In-Reply-To: <9069bd9d83653fbb286f9e8fa53827b1639d1923.camel@mediatek.com>

Quoting CK Hu (2022-02-25 10:45:26)
> Hi, Guillaume:
>
> On Fri, 2022-02-18 at 15:54 +0100, Guillaume Ranquet wrote:
> > From: Markus Schneider-Pargmann <msp@baylibre.com>
> >
> > This patch adds a DisplayPort driver for the Mediatek mt8195 SoC.
> >
> > It supports the mt8195, the embedded DisplayPort units. It offers
> > hot-plug-detection and DisplayPort 1.4 with up to 4 lanes.
> >
> > The driver creates a child device for the phy. The child device will
> > never exist without the parent being active. As they are sharing a
> > register range, the parent passes a regmap pointer to the child so
> > that
> > both can work with the same register range. The phy driver sets
> > device
> > data that is read by the parent to get the phy device that can be
> > used
> > to control the phy properties.
> >
> > This driver is based on an initial version by
> > Jason-JH.Lin <jason-jh.lin@mediatek.com>.
> >
> > Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> > Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> > Reported-by: kernel test robot <lkp@intel.com>
> > ---
> >  drivers/gpu/drm/mediatek/Kconfig       |    7 +
> >  drivers/gpu/drm/mediatek/Makefile      |    2 +
> >  drivers/gpu/drm/mediatek/mtk_dp.c      | 2358
> > ++++++++++++++++++++++++
> >  drivers/gpu/drm/mediatek/mtk_dp_reg.h  |  568 ++++++
> >  drivers/gpu/drm/mediatek/mtk_drm_drv.c |    1 +
> >  drivers/gpu/drm/mediatek/mtk_drm_drv.h |    1 +
> >  6 files changed, 2937 insertions(+)
> >  create mode 100644 drivers/gpu/drm/mediatek/mtk_dp.c
> >  create mode 100644 drivers/gpu/drm/mediatek/mtk_dp_reg.h
> >
> >
>
> [snip]
>
> > +
> > +static u32 *mtk_dp_bridge_atomic_get_output_bus_fmts(struct
> > drm_bridge *bridge,
> > +                                                  struct
> > drm_bridge_state *bridge_state,
> > +                                                  struct
> > drm_crtc_state *crtc_state,
> > +                                                  struct
> > drm_connector_state *conn_state,
> > +                                                  unsigned int
> > *num_output_fmts)
> > +{
> > +     u32 *output_fmts;
> > +
> > +     *num_output_fmts = 0;
> > +     output_fmts = kcalloc(1, sizeof(*output_fmts), GFP_KERNEL);
> > +     if (!output_fmts)
> > +             return NULL;
> > +     *num_output_fmts = 1;
> > +     output_fmts[0] = MEDIA_BUS_FMT_FIXED;
> > +     return output_fmts;
> > +}
> > +
> > +static const u32 mt8195_input_fmts[] = {
> > +     MEDIA_BUS_FMT_RGB888_1X24,
> > +     MEDIA_BUS_FMT_YUV8_1X24,
> > +     MEDIA_BUS_FMT_YUYV8_1X16,
> > +};
>
> This means DPINTF output format, right? Does DPINTF switch output
> buffer format?
>
I'll circle back with mediatek engineers, as I don't have a clue here.

> > +
> > +static u32 *mtk_dp_bridge_atomic_get_input_bus_fmts(struct
> > drm_bridge *bridge,
> > +                                                 struct
> > drm_bridge_state *bridge_state,
> > +                                                 struct
> > drm_crtc_state *crtc_state,
> > +                                                 struct
> > drm_connector_state *conn_state,
> > +                                                 u32 output_fmt,
> > +                                                 unsigned int
> > *num_input_fmts)
> > +{
> > +     u32 *input_fmts;
> > +     struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
> > +     struct drm_display_mode *mode = &crtc_state->adjusted_mode;
> > +     struct drm_display_info *display_info =
> > +             &conn_state->connector->display_info;
> > +     u32 rx_linkrate;
> > +     u32 bpp;
> > +
> > +     bpp = (display_info->color_formats & DRM_COLOR_FORMAT_YCRCB422)
> > ? 16 :
> > +
> >       24;
> > +     rx_linkrate = (u32)mtk_dp->train_info.link_rate * 27000;
> > +     *num_input_fmts = 0;
> > +     input_fmts = kcalloc(ARRAY_SIZE(mt8195_input_fmts),
> > sizeof(*input_fmts),
> > +                          GFP_KERNEL);
> > +     if (!input_fmts)
> > +             return NULL;
> > +
> > +     *num_input_fmts = ARRAY_SIZE(mt8195_input_fmts);
> > +
> > +     memcpy(input_fmts, mt8195_input_fmts,
> > +            sizeof(*input_fmts) * ARRAY_SIZE(mt8195_input_fmts));
> > +
> > +     if (((rx_linkrate * mtk_dp->train_info.lane_count) <
> > +          (mode->clock * 24 / 8)) &&
> > +         ((rx_linkrate * mtk_dp->train_info.lane_count) >
> > +          (mode->clock * 16 / 8)) &&
> > +         (display_info->color_formats & DRM_COLOR_FORMAT_YCRCB422))
> > {
> > +             kfree(input_fmts);
> > +             input_fmts = kcalloc(1, sizeof(*input_fmts),
> > GFP_KERNEL);
> > +             *num_input_fmts = 1;
> > +             input_fmts[0] = MEDIA_BUS_FMT_YUYV8_1X16;
> > +     }
> > +
> > +     return input_fmts;
> > +}
> > +
>
> [snip]
>
> > +
> > +static int mtk_dp_probe(struct platform_device *pdev)
> > +{
> > +     struct mtk_dp *mtk_dp;
> > +     struct device *dev = &pdev->dev;
> > +     int ret;
> > +     int irq_num = 0;
> > +
> > +     mtk_dp = devm_kzalloc(dev, sizeof(*mtk_dp), GFP_KERNEL);
> > +     if (!mtk_dp)
> > +             return -ENOMEM;
> > +
> > +     mtk_dp->dev = dev;
> > +
> > +     irq_num = platform_get_irq(pdev, 0);
> > +     if (irq_num < 0) {
> > +             dev_err(dev, "failed to request dp irq resource\n");
> > +             return irq_num;
> > +     }
> > +
> > +     mtk_dp->next_bridge = devm_drm_of_get_bridge(dev, dev->of_node,
> > 1, 0);
> > +     if (IS_ERR(mtk_dp->next_bridge)) {
> > +             ret = PTR_ERR(mtk_dp->next_bridge);
> > +             dev_err_probe(dev, ret, "Failed to get bridge\n");
> > +             return ret;
> > +     }
> > +
> > +     ret = mtk_dp_dt_parse(mtk_dp, pdev);
> > +     if (ret)
> > +             return ret;
> > +
> > +     mtk_dp_aux_init(mtk_dp);
> > +
> > +     ret = devm_request_threaded_irq(dev, irq_num, mtk_dp_hpd_event,
> > +                                     mtk_dp_hpd_event_thread,
> > +                                     IRQ_TYPE_LEVEL_HIGH,
> > dev_name(dev),
> > +                                     mtk_dp);
>
> Embedded displayport is always connected, right? Why do we need process
> hot plug? Move this to the patch of external displayport.
>
That was my initial plan, remove all the HPD related "stuff"... but something
is being done in the irq that is needed to get eDP working.
I haven't been able to retrieve the EDID with the irq removed.

As I'm not knowledgeable in this domain or on the architecture, I couldn't
get to the bottom of it with the available documentation I have.

Probably something is done in the irq for eDP that should happen outside?
I will try for v9 to remove hot plug detection entirely for the
initial eDP support.

> > +     if (ret) {
> > +             dev_err(dev, "failed to request mediatek dptx irq\n");
> > +             return -EPROBE_DEFER;
> > +     }
> > +
> > +     mutex_init(&mtk_dp->dp_lock);
>
> Why need dp_lock, please provide the case information.
>
> > +     mutex_init(&mtk_dp->edid_lock);
>
> edid_lock is necessary when irq exist.
>
> > +
> > +     platform_set_drvdata(pdev, mtk_dp);
> > +
> > +     mtk_dp->phy_dev = platform_device_register_data(dev, "mediatek-
> > dp-phy",
> > +                                                     PLATFORM_DEVID_
> > AUTO,
> > +                                                     &mtk_dp->regs,
> > +                                                     sizeof(struct
> > regmap *));
> > +     if (IS_ERR(mtk_dp->phy_dev)) {
> > +             dev_err(dev, "Failed to create device mediatek-dp-phy:
> > %ld\n",
> > +                     PTR_ERR(mtk_dp->phy_dev));
> > +             return PTR_ERR(mtk_dp->phy_dev);
> > +     }
> > +
> > +     mtk_dp_get_calibration_data(mtk_dp);
> > +
> > +     mtk_dp->phy = devm_phy_get(&mtk_dp->phy_dev->dev, "dp");
> > +     if (IS_ERR(mtk_dp->phy)) {
> > +             dev_err(dev, "Failed to get phy: %ld\n",
> > PTR_ERR(mtk_dp->phy));
> > +             platform_device_unregister(mtk_dp->phy_dev);
> > +             return PTR_ERR(mtk_dp->phy);
> > +     }
> > +
> > +     mtk_dp->bridge.funcs = &mtk_dp_bridge_funcs;
> > +     mtk_dp->bridge.of_node = dev->of_node;
> > +     mtk_dp->bridge.type = DRM_MODE_CONNECTOR_eDP;
> > +
> > +     mtk_dp->bridge.ops =
> > +             DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID |
> > DRM_BRIDGE_OP_HPD;
>
> DRM_BRIDGE_OP_DETECT? DRM_BRIDGE_OP_HPD?
>
> > +     drm_bridge_add(&mtk_dp->bridge);
> > +
> > +     pm_runtime_enable(dev);
> > +     pm_runtime_get_sync(dev);
> > +
> > +     return 0;
> > +}
> > +
> >
>
> [snip]
>
> > diff --git a/drivers/gpu/drm/mediatek/mtk_dp_reg.h
> > b/drivers/gpu/drm/mediatek/mtk_dp_reg.h
> > new file mode 100644
> > index 0000000000000..79952ac30e9e6
> > --- /dev/null
> > +++ b/drivers/gpu/drm/mediatek/mtk_dp_reg.h
> > @@ -0,0 +1,568 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (c) 2019 MediaTek Inc.
> > + * Copyright (c) 2021 BayLibre
> > + */
> > +#ifndef _MTK_DP_REG_H_
> > +#define _MTK_DP_REG_H_
> > +
> > +#define MTK_DP_SIP_CONTROL_AARCH32 0x82000523
> > +#define MTK_DP_SIP_ATF_VIDEO_UNMUTE 0x20
> > +#define MTK_DP_SIP_ATF_EDP_VIDEO_UNMUTE 0x21
> > +
> > +#define DP_PHY_GLB_BIAS_GEN_00 0x0000
> > +#define RG_XTP_GLB_BIAS_INTR_CTRL (0x1f << 16)
> > +
> > +#define DP_PHY_GLB_DPAUX_TX 0x0008
> > +#define RG_CKM_PT0_CKTX_IMPSEL (0xf << 20)
> > +
> > +#define DP_PHY_LANE_TX_0 0x104
> > +#define RG_XTP_LN0_TX_IMPSEL_PMOS (0xf << 12)
> > +#define RG_XTP_LN0_TX_IMPSEL_NMOS (0xf << 16)
> > +
> > +#define DP_PHY_LANE_TX_1 0x204
> > +#define RG_XTP_LN1_TX_IMPSEL_PMOS (0xf << 12)
> > +#define RG_XTP_LN1_TX_IMPSEL_NMOS (0xf << 16)
> > +
> > +#define DP_PHY_LANE_TX_2 0x304
> > +#define RG_XTP_LN2_TX_IMPSEL_PMOS (0xf << 12)
> > +#define RG_XTP_LN2_TX_IMPSEL_NMOS (0xf << 16)
> > +
> > +#define DP_PHY_LANE_TX_3 0x404
> > +#define RG_XTP_LN3_TX_IMPSEL_PMOS (0xf << 12)
> > +#define RG_XTP_LN3_TX_IMPSEL_NMOS (0xf << 16)
>
> These register should be controlled by dp_phy driver?
>
> Regards,
> CK
>
> > +
> > +#define TOP_OFFSET 0x2000
> > +#define ENC0_OFFSET 0x3000
> > +#define ENC1_OFFSET 0x3200
> > +#define TRANS_OFFSET 0x3400
> > +#define AUX_OFFSET 0x3600
> > +#define SEC_OFFSET 0x4000
> > +
> >
>