Re: [PATCH v5 02/16] phy: Distinguish between Rx and Tx for MIPI D-PHY with submodes
From: Paul Kocialkowski <hidden>
Date: 2021-05-26 14:24:10
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Hi everyone, On Fri 15 Jan 21, 21:01, Paul Kocialkowski wrote:
As some D-PHY controllers support both Rx and Tx mode, we need a way for users to explicitly request one or the other. For instance, Rx mode can be used along with MIPI CSI-2 while Tx mode can be used with MIPI DSI. Introduce new MIPI D-PHY PHY submodes to use with PHY_MODE_MIPI_DPHY. The default (zero value) is kept to Tx so only the rkisp1 driver, which uses D-PHY in Rx mode, needs to be adapted.
I think it was Laurent who brought up on IRC that using a submode is probably not a correct way to distinguish between Rx and Tx modes. Thinking about it again, it feels like selecting the direction at run-time would only be relevant if there's D-PHY hardware than can do both Tx and Rx *and* that can be muxed to either a MIPI DSI and a CSI-2 controller at run-time. For the Allwinner case, the D-PHY is the same hardware for both but there will be one instance attached to each controller, not a single shared instance. It feels rather unlikely that a device with both MIPI DSI and CSI-2 would only have one PHY for the two as this wouldn't allow concurrent use of the two controllers. Even in a case where there'd be n controllers and m < n bi-directional PHYs, it feels safe to assume that a static attribution would be sufficient. As a result it feels more relevant to have this distinction in device-tree rather than via the PHY API. What do you think? Any suggestion on how this should be represented in device-tree? Cheers, Paul
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Signed-off-by: Paul Kocialkowski <redacted> Acked-by: Helen Koike <redacted> --- drivers/media/platform/rockchip/rkisp1/rkisp1-isp.c | 3 ++- include/linux/phy/phy-mipi-dphy.h | 13 +++++++++++++ 2 files changed, 15 insertions(+), 1 deletion(-)diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-isp.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-isp.c index 2e5b57e3aedc..cab261644102 100644 --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-isp.c +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-isp.c@@ -948,7 +948,8 @@ static int rkisp1_mipi_csi2_start(struct rkisp1_isp *isp, phy_mipi_dphy_get_default_config(pixel_clock, isp->sink_fmt->bus_width, sensor->lanes, cfg); - phy_set_mode(sensor->dphy, PHY_MODE_MIPI_DPHY); + phy_set_mode_ext(cdev->dphy, PHY_MODE_MIPI_DPHY, + PHY_MIPI_DPHY_SUBMODE_RX); phy_configure(sensor->dphy, &opts); phy_power_on(sensor->dphy);diff --git a/include/linux/phy/phy-mipi-dphy.h b/include/linux/phy/phy-mipi-dphy.h index a877ffee845d..0f57ef46a8b5 100644 --- a/include/linux/phy/phy-mipi-dphy.h +++ b/include/linux/phy/phy-mipi-dphy.h@@ -6,6 +6,19 @@ #ifndef __PHY_MIPI_DPHY_H_ #define __PHY_MIPI_DPHY_H_ +/** + * enum phy_mipi_dphy_submode - MIPI D-PHY sub-mode + * + * A MIPI D-PHY can be used to transmit or receive data. + * Since some controllers can support both, the direction to enable is specified + * with the PHY sub-mode. Transmit is assumed by default with phy_set_mode. + */ + +enum phy_mipi_dphy_submode { + PHY_MIPI_DPHY_SUBMODE_TX = 0, + PHY_MIPI_DPHY_SUBMODE_RX, +}; + /** * struct phy_configure_opts_mipi_dphy - MIPI D-PHY configuration set *-- 2.30.0
-- Paul Kocialkowski, Bootlin Embedded Linux and kernel engineering https://bootlin.com