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Message-ID: <hkz5zdhy7i6tmmpntvqydck6fnpegpbletfwj6h7mtppkw3qub@bzfvf2vfcudj>
Date: Thu, 21 Aug 2025 14:38:43 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Icenowy Zheng <uwu@...nowy.me>
Cc: Troy Mitchell <troy.mitchell@...ux.spacemit.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Drew Fustini <fustini@...nel.org>,
Guo Ren <guoren@...nel.org>, Fu Wei <wefu@...hat.com>,
Philipp Zabel <p.zabel@...gutronix.de>,
Heiko Stuebner <heiko@...ech.de>,
Andrzej Hajda <andrzej.hajda@...el.com>,
Neil Armstrong <neil.armstrong@...aro.org>,
Robert Foss <rfoss@...nel.org>,
Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
Jonas Karlman <jonas@...boo.se>,
Jernej Skrabec <jernej.skrabec@...il.com>,
Michal Wilczynski <m.wilczynski@...sung.com>,
Han Gao <rabenda.cn@...il.com>, Yao Zi <ziyao@...root.org>,
dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [RFC PATCH 5/8] drm/bridge: add a driver for T-Head TH1520 HDMI
controller
On Mon, Aug 18, 2025 at 03:47:28PM +0800, Icenowy Zheng wrote:
> 在 2025-08-18星期一的 15:45 +0800，Troy Mitchell写道：
> > On Sun, Aug 17, 2025 at 01:10:44AM +0800, Icenowy Zheng wrote:
> > > 在 2025-08-16星期六的 19:24 +0300，Dmitry Baryshkov写道：
> > > > On Fri, Aug 15, 2025 at 12:40:45AM +0800, Icenowy Zheng wrote:
> > > > > T-Head TH1520 SoC contains a Synopsys DesignWare HDMI
> > > > > controller
> > > > > (paired
> > > > > with DesignWare HDMI TX PHY Gen2) that takes the "DP" output
> > > > > from
> > > > > the
> > > > > display controller.
> > > > >
> > > > > Add a driver for this controller utilizing the common
> > > > > DesignWare
> > > > > HDMI
> > > > > code in the kernel.
> > > > >
> > > > > Signed-off-by: Icenowy Zheng <uwu@...nowy.me>
> > > > > ---
> > > > > MAINTAINERS | 1 +
> > > > > drivers/gpu/drm/bridge/Kconfig | 10 ++
> > > > > drivers/gpu/drm/bridge/Makefile | 1 +
> > > > > drivers/gpu/drm/bridge/th1520-dw-hdmi.c | 170
> > > > > ++++++++++++++++++++++++
> > > > > 4 files changed, 182 insertions(+)
> > > > > create mode 100644 drivers/gpu/drm/bridge/th1520-dw-hdmi.c
> > > > >
> > > > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > > > index fe168477caa45..eb84e36ded6d5 100644
> > > > > --- a/MAINTAINERS
> > > > > +++ b/MAINTAINERS
> > > > > @@ -21728,6 +21728,7 @@
> > > > > F: Documentation/devicetree/bindings/reset/thead,th1520-
> > > > > reset.yaml
> > > > > F: arch/riscv/boot/dts/thead/
> > > > > F: drivers/clk/thead/clk-th1520-ap.c
> > > > > F: drivers/firmware/thead,th1520-aon.c
> > > > > +F: drivers/gpu/drm/bridge/th1520-dw-hdmi.c
> > > > > F: drivers/mailbox/mailbox-th1520.c
> > > > > F: drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
> > > > > F: drivers/pinctrl/pinctrl-th1520.c
> > > > > diff --git a/drivers/gpu/drm/bridge/Kconfig
> > > > > b/drivers/gpu/drm/bridge/Kconfig
> > > > > index b9e0ca85226a6..f75e6ad04179f 100644
> > > > > --- a/drivers/gpu/drm/bridge/Kconfig
> > > > > +++ b/drivers/gpu/drm/bridge/Kconfig
> > > > > @@ -322,6 +322,16 @@ config DRM_THINE_THC63LVD1024
> > > > > help
> > > > > Thine THC63LVD1024 LVDS/parallel converter driver.
> > > > >
> > > > > +config DRM_THEAD_TH1520_DW_HDMI
> > > > > + tristate "T-Head TH1520 DesignWare HDMI bridge"
> > > > > + depends on OF
> > > > > + depends on COMMON_CLK
> > > > > + depends on ARCH_THEAD || COMPILE_TEST
> > > > > + select DRM_DW_HDMI
> > > > > + help
> > > > > + Choose this to enable support for the internal HDMI
> > > > > bridge found
> > > > > + on the T-Head TH1520 SoC.
> > > > > +
> > > > > config DRM_TOSHIBA_TC358762
> > > > > tristate "TC358762 DSI/DPI bridge"
> > > > > depends on OF
> > > > > diff --git a/drivers/gpu/drm/bridge/Makefile
> > > > > b/drivers/gpu/drm/bridge/Makefile
> > > > > index 245e8a27e3fc5..421e445ff1cd9 100644
> > > > > --- a/drivers/gpu/drm/bridge/Makefile
> > > > > +++ b/drivers/gpu/drm/bridge/Makefile
> > > > > @@ -27,6 +27,7 @@ obj-$(CONFIG_DRM_SIL_SII8620) += sil-
> > > > > sii8620.o
> > > > > obj-$(CONFIG_DRM_SII902X) += sii902x.o
> > > > > obj-$(CONFIG_DRM_SII9234) += sii9234.o
> > > > > obj-$(CONFIG_DRM_SIMPLE_BRIDGE) += simple-bridge.o
> > > > > +obj-$(CONFIG_DRM_THEAD_TH1520_DW_HDMI) += th1520-dw-hdmi.o
> > > > > obj-$(CONFIG_DRM_THINE_THC63LVD1024) += thc63lvd1024.o
> > > > > obj-$(CONFIG_DRM_TOSHIBA_TC358762) += tc358762.o
> > > > > obj-$(CONFIG_DRM_TOSHIBA_TC358764) += tc358764.o
> > > > > diff --git a/drivers/gpu/drm/bridge/th1520-dw-hdmi.c
> > > > > b/drivers/gpu/drm/bridge/th1520-dw-hdmi.c
> > > > > new file mode 100644
> > > > > index 0000000000000..f8dddf3cb0cca
> > > > > --- /dev/null
> > > > > +++ b/drivers/gpu/drm/bridge/th1520-dw-hdmi.c
> > > > > @@ -0,0 +1,170 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0+
> > > > > +/*
> > > > > + * Copyright (C) 2025 Icenowy Zheng <uwu@...nowy.me>
> > > > > + *
> > > > > + * Based on rcar_dw_hdmi.c, which is:
> > > > > + * Copyright (C) 2016 Renesas Electronics Corporation
> > > > > + * Based on imx8mp-hdmi-tx.c, which is:
> > > > > + * Copyright (C) 2022 Pengutronix, Lucas Stach
> > > > > <kernel@...gutronix.de>
> > > > > + */
> > > > > +
> > > > > +#include <linux/clk.h>
> > > > > +#include <linux/mod_devicetable.h>
> > > > > +#include <linux/module.h>
> > > > > +#include <linux/platform_device.h>
> > > > > +#include <linux/reset.h>
> > > > > +
> > > > > +#include <drm/bridge/dw_hdmi.h>
> > > > > +#include <drm/drm_modes.h>
> > > > > +
> > > > > +#define TH1520_HDMI_PHY_OPMODE_PLLCFG 0x06 /* Mode of
> > > > > operation and PLL dividers */
> > > > > +#define TH1520_HDMI_PHY_CKSYMTXCTRL 0x09 /* Clock Symbol
> > > > > and
> > > > > Transmitter Control Register */
> > > > > +#define TH1520_HDMI_PHY_VLEVCTRL 0x0e /* Voltage
> > > > > Level
> > > > > Control Register */
> > > > > +#define TH1520_HDMI_PHY_PLLCURRGMPCTRL 0x10 /* PLL current
> > > > > and
> > > > > Gmp (conductance) */
> > > > > +#define TH1520_HDMI_PHY_PLLDIVCTRL 0x11 /* PLL dividers
> > > > > */
> > > > > +#define TH1520_HDMI_PHY_TXTERM 0x19 /* Transmission
> > > > > Termination Register */
> > > > > +
> > > > > +struct th1520_hdmi_phy_params {
> > > > > + unsigned long mpixelclock;
> > > > > + u16 opmode_pllcfg;
> > > > > + u16 pllcurrgmpctrl;
> > > > > + u16 plldivctrl;
> > > > > + u16 cksymtxctrl;
> > > > > + u16 vlevctrl;
> > > > > + u16 txterm;
> > > > > +};
> > > > > +
> > > > > +static const struct th1520_hdmi_phy_params
> > > > > th1520_hdmi_phy_params[] = {
> > > > > + { 35500000, 0x0003, 0x0283, 0x0628, 0x8088, 0x01a0,
> > > > > 0x0007
> > > > > },
> > > > > + { 44900000, 0x0003, 0x0285, 0x0228, 0x8088, 0x01a0,
> > > > > 0x0007
> > > > > },
> > > > > + { 71000000, 0x0002, 0x1183, 0x0614, 0x8088, 0x01a0,
> > > > > 0x0007
> > > > > },
> > > > > + { 90000000, 0x0002, 0x1142, 0x0214, 0x8088, 0x01a0,
> > > > > 0x0007
> > > > > },
> > > > > + { 121750000, 0x0001, 0x20c0, 0x060a, 0x8088, 0x01a0,
> > > > > 0x0007
> > > > > },
> > > > > + { 165000000, 0x0001, 0x2080, 0x020a, 0x8088, 0x01a0,
> > > > > 0x0007
> > > > > },
> > > > > + { 198000000, 0x0000, 0x3040, 0x0605, 0x83c8, 0x0120,
> > > > > 0x0004
> > > > > },
> > > > > + { 297000000, 0x0000, 0x3041, 0x0205, 0x81dc, 0x0200,
> > > > > 0x0005
> > > > > },
> > > > > + { 371250000, 0x0640, 0x3041, 0x0205, 0x80f6, 0x0140,
> > > > > 0x0000
> > > > > },
> > > > > + { 495000000, 0x0640, 0x3080, 0x0005, 0x80f6, 0x0140,
> > > > > 0x0000
> > > > > },
> > > > > + { 594000000, 0x0640, 0x3080, 0x0005, 0x80fa, 0x01e0,
> > > > > 0x0004
> > > > > },
> > > > > + { ~0UL, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
> > > > > 0x0000
> > > > > }
> > > > > +};
> > > > > +
> > > > > +struct th1520_hdmi {
> > > > > + struct dw_hdmi_plat_data plat_data;
> > > > > + struct dw_hdmi *dw_hdmi;
> > > > > + struct clk *pixclk;
> > > > > + struct reset_control *mainrst, *prst;
> > > > > +};
> > > > > +
> > > > > +static enum drm_mode_status
> > > > > +th1520_hdmi_mode_valid(struct dw_hdmi *hdmi, void *data,
> > > > > + const struct drm_display_info *info,
> > > > > + const struct drm_display_mode *mode)
> > > > > +{
> > > > > + /*
> > > > > + * The maximum supported clock frequency is 594 MHz, as
> > > > > shown in the PHY
> > > > > + * parameters table.
> > > > > + */
> > > > > + if (mode->clock > 594000)
> > > > > + return MODE_CLOCK_HIGH;
> > > >
> > > > We should rewrite DW bridge into HDMI ops. It would help us to
> > > > get
> > > > rid
> > > > of such functions. With it in place it will be handled by the
> > > > generic
> > > > TMDS clock rate check.
> > >
> > > Yes, but this mode_valid hook here is part of the private interface
> > > of
> > > DW bridge, instead of implementing anything for other parts of DRM
> > > subsystem.
> > >
> > > Even if the TMDS clock rate check is utilized by the DW bridge, the
> > > bridge's interface should be modified to expose something to set
> > > the
> > > maximum clock rate.
> > >
> > > >
> > > > > +
> > > > > + return MODE_OK;
> > > > > +}
> > > > > +
> > > > > +static int th1520_hdmi_phy_configure(struct dw_hdmi *hdmi,
> > > > > void
> > > > > *data,
> > > > > + unsigned long mpixelclock)
> > > > > +{
> > > > > + const struct th1520_hdmi_phy_params *params =
> > > > > th1520_hdmi_phy_params;
> > > > > +
> > > > > + for (; params->mpixelclock != ~0UL; ++params) {
> > > > > + if (mpixelclock <= params->mpixelclock)
> > > > > + break;
> > > >
> > > > for (...) {
> > > > if (mpixelclock <= params->mpixelclock)
> > > > return th1520_program_phy();
> > >
> > > There's no such a function here, and this check isn't used for
> > > another
> > > time, so having the matching code and programming code extracted
> > > out
> > > can help nothing.
> > I think Dmitry meant that the following code should be moved into
> > a new function, th1520_program_phy().
> >
> > This makes the code cleaner and also avoids one extra if check.
>
> As there's no code reuse, it does not make code cleaner.
It removes necessity for the extra ~0UL entry in the array and removes
the post-loop check whether we found an entry or not.
--
With best wishes
Dmitry
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