On Mon, Dec 16, 2019 at 4:46 PM Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote: > > On Sat, Dec 14, 2019 at 6:38 AM Laurent Pinchart > <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > > > > Hi Hsin-Yi and Nicolas, > > > > Thank you for the patch. > > > > On Wed, Dec 11, 2019 at 02:19:09PM +0800, Hsin-Yi Wang wrote: > > > From: Nicolas Boichat <drinkcat@xxxxxxxxxxxx> > > > > > > ANX7688 is a HDMI to DP converter (as well as USB-C port controller), > > > that has an internal microcontroller. > > > > > > The only reason a Linux kernel driver is necessary is to reject > > > resolutions that require more bandwidth than what is available on > > > the DP side. DP bandwidth and lane count are reported by the bridge > > > via 2 registers on I2C. > > > > How about power, doesn't this chip have power supplies that potentially > > need to be controlled ? > > > Ideally we should add power supplies as well, but the power is > supplied by ec in mt8173 oak board. And we only have this board can > test this driver. If we add power supplies in driver we can't test it. To clarify a bit more, this is because this chip is actually a TCPC+mux+HDMI=>DP converter (https://www.analogix.com/en/products/convertersbridges/anx7688). In Chromebook architecture, TCPC+mux is controlled by the EC (including power and other control pins), and the only reason we need a driver for the HDMI=>DP converter is to get the number of lanes on the DP side and filter out resolutions. Also, the converter is on a different I2C address and it could almost be considered as a separate device. (of course we could write a kernel driver for the TCPC+mux but we'll leave that to others if there's ever a board that is built with the TCPC part connected to the AP) > > > Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx> > > > Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> > > > --- > > > drivers/gpu/drm/bridge/Kconfig | 9 + > > > drivers/gpu/drm/bridge/Makefile | 1 + > > > drivers/gpu/drm/bridge/analogix-anx7688.c | 202 ++++++++++++++++++++++ > > > 3 files changed, 212 insertions(+) > > > create mode 100644 drivers/gpu/drm/bridge/analogix-anx7688.c > > > > > > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig > > > index 34362976cd6f..1f3fc6bec842 100644 > > > --- a/drivers/gpu/drm/bridge/Kconfig > > > +++ b/drivers/gpu/drm/bridge/Kconfig > > > @@ -16,6 +16,15 @@ config DRM_PANEL_BRIDGE > > > menu "Display Interface Bridges" > > > depends on DRM && DRM_BRIDGE > > > > > > +config DRM_ANALOGIX_ANX7688 > > > + tristate "Analogix ANX7688 bridge" > > > + select DRM_KMS_HELPER > > > + select REGMAP_I2C > > > + ---help--- > > > + ANX7688 is a transmitter to support DisplayPort over USB-C for > > > + smartphone and tablets. > > > + This driver only supports the HDMI to DP component of the chip. > > > + > > > config DRM_ANALOGIX_ANX78XX > > > tristate "Analogix ANX78XX bridge" > > > select DRM_KMS_HELPER > > > diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile > > > index 4934fcf5a6f8..7a1e0ec032e6 100644 > > > --- a/drivers/gpu/drm/bridge/Makefile > > > +++ b/drivers/gpu/drm/bridge/Makefile > > > @@ -1,4 +1,5 @@ > > > # SPDX-License-Identifier: GPL-2.0 > > > +obj-$(CONFIG_DRM_ANALOGIX_ANX7688) += analogix-anx7688.o > > > obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o > > > obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o > > > obj-$(CONFIG_DRM_DUMB_VGA_DAC) += dumb-vga-dac.o > > > diff --git a/drivers/gpu/drm/bridge/analogix-anx7688.c b/drivers/gpu/drm/bridge/analogix-anx7688.c > > > new file mode 100644 > > > index 000000000000..baaed48d6201 > > > --- /dev/null > > > +++ b/drivers/gpu/drm/bridge/analogix-anx7688.c > > > @@ -0,0 +1,202 @@ > > > +// SPDX-License-Identifier: GPL-2.0-only > > > +/* > > > + * ANX7688 HDMI->DP bridge driver > > > + * > > > + * Copyright 2016 Google LLC > > > + */ > > > + > > > +#include <linux/i2c.h> > > > +#include <linux/module.h> > > > +#include <linux/regmap.h> > > > +#include <drm/drm_bridge.h> > > > + > > > +/* Register addresses */ > > > +#define VENDOR_ID_REG 0x00 > > > +#define DEVICE_ID_REG 0x02 > > > + > > > +#define FW_VERSION_REG 0x80 > > > + > > > +#define DP_BANDWIDTH_REG 0x85 > > > +#define DP_LANE_COUNT_REG 0x86 > > > > Are these registers defined by the ANX7688 hardware, or by the firmware > > running on the chip (and, I assume, developed by Google) ? > > > By firmware developed by ANX provided to Google. We asked for these registers to be added to ANX FW, and this is the FW that is used by all elm/hana Chromebooks (I have no idea about other ANX customers...). We have facilities to update the ANX FW from coreboot/depthcharge on Chromebooks, but that does not really matter: the factory FW of all MP Chromebooks does provide these registers. Thanks.
