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SubjectRe: [PATCH 04/10] phy: dphy: Add configuration helpers
Date
Hi Maxime,

Thank you for the patch.

On Wednesday, 5 September 2018 12:16:35 EEST Maxime Ripard wrote:
> The MIPI D-PHY spec defines default values and boundaries for most of the
> parameters it defines. Introduce helpers to help drivers get meaningful
> values based on their current parameters, and validate the boundaries of
> these parameters if needed.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> ---
> drivers/phy/Kconfig | 8 ++-
> drivers/phy/Makefile | 1 +-
> drivers/phy/phy-core-mipi-dphy.c | 160 +++++++++++++++++++++++++++++++-
> include/linux/phy/phy-mipi-dphy.h | 6 +-
> 4 files changed, 175 insertions(+)
> create mode 100644 drivers/phy/phy-core-mipi-dphy.c
>
> diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
> index 5c8d452e35e2..06bd22bd1f4a 100644
> --- a/drivers/phy/Kconfig
> +++ b/drivers/phy/Kconfig
> @@ -15,6 +15,14 @@ config GENERIC_PHY
> phy users can obtain reference to the PHY. All the users of this
> framework should select this config.
>
> +config GENERIC_PHY_MIPI_DPHY
> + bool "MIPI D-PHY support"
> + help
> + Generic MIPI D-PHY support.
> +
> + Provides a number of helpers a core functions for MIPI D-PHY
> + drivers to us.

Do we really need to make this user-selectable ?

> config PHY_LPC18XX_USB_OTG
> tristate "NXP LPC18xx/43xx SoC USB OTG PHY driver"
> depends on OF && (ARCH_LPC18XX || COMPILE_TEST)
> diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile
> index 84e3bd9c5665..71c29d2b9af7 100644
> --- a/drivers/phy/Makefile
> +++ b/drivers/phy/Makefile
> @@ -4,6 +4,7 @@
> #
>
> obj-$(CONFIG_GENERIC_PHY) += phy-core.o
> +obj-$(CONFIG_GENERIC_PHY_MIPI_DPHY) += phy-core-mipi-dphy.o
> obj-$(CONFIG_PHY_LPC18XX_USB_OTG) += phy-lpc18xx-usb-otg.o
> obj-$(CONFIG_PHY_XGENE) += phy-xgene.o
> obj-$(CONFIG_PHY_PISTACHIO_USB) += phy-pistachio-usb.o
> diff --git a/drivers/phy/phy-core-mipi-dphy.c
> b/drivers/phy/phy-core-mipi-dphy.c new file mode 100644
> index 000000000000..6c1ddc7734a2
> --- /dev/null
> +++ b/drivers/phy/phy-core-mipi-dphy.c
> @@ -0,0 +1,160 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2013 NVIDIA Corporation
> + * Copyright (C) 2018 Cadence Design Systems Inc.
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/export.h>
> +#include <linux/kernel.h>
> +#include <linux/time64.h>
> +
> +#include <linux/phy/phy.h>
> +#include <linux/phy/phy-mipi-dphy.h>
> +
> +/*
> + * Default D-PHY timings based on MIPI D-PHY specification. Derived from
> the
> + * valid ranges specified in Section 6.9, Table 14, Page 40 of the D-PHY
> + * specification (v1.2) with minor adjustments.

Could you list those adjustments ?

> + */
> +int phy_mipi_dphy_get_default_config(unsigned long pixel_clock,
> + unsigned int bpp,
> + unsigned int lanes,
> + struct phy_configure_opts_mipi_dphy *cfg)
> +{
> + unsigned long hs_clk_rate;
> + unsigned long ui;
> +
> + if (!cfg)
> + return -EINVAL;

Should we really expect cfg to be NULL ?

> + hs_clk_rate = pixel_clock * bpp / lanes;
> + ui = DIV_ROUND_UP(NSEC_PER_SEC, hs_clk_rate);
> +
> + cfg->clk_miss = 0;
> + cfg->clk_post = 70 + 52 * ui;
> + cfg->clk_pre = 8;
> + cfg->clk_prepare = 65;
> + cfg->clk_settle = 95;
> + cfg->clk_term_en = 0;
> + cfg->clk_trail = 80;
> + cfg->clk_zero = 260;
> + cfg->d_term_en = 0;
> + cfg->eot = 0;
> + cfg->hs_exit = 120;
> + cfg->hs_prepare = 65 + 5 * ui;
> + cfg->hs_zero = 145 + 5 * ui;
> + cfg->hs_settle = 85 + 6 * ui;
> + cfg->hs_skip = 40;
> +
> + /*
> + * The MIPI D-PHY specification (Section 6.9, v1.2, Table 14, Page 40)
> + * contains this formula as:
> + *
> + * T_HS-TRAIL = max(n * 8 * ui, 60 + n * 4 * ui)
> + *
> + * where n = 1 for forward-direction HS mode and n = 4 for reverse-
> + * direction HS mode. There's only one setting and this function does
> + * not parameterize on anything other that ui, so this code will
> + * assumes that reverse-direction HS mode is supported and uses n = 4.
> + */
> + cfg->hs_trail = max(4 * 8 * ui, 60 + 4 * 4 * ui);
> +
> + cfg->init = 100000;
> + cfg->lpx = 60;
> + cfg->ta_get = 5 * cfg->lpx;
> + cfg->ta_go = 4 * cfg->lpx;
> + cfg->ta_sure = 2 * cfg->lpx;
> + cfg->wakeup = 1000000;
> +
> + cfg->hs_clk_rate = hs_clk_rate;
> + cfg->lanes = lanes;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(phy_mipi_dphy_get_default_config);
> +
> +/*
> + * Validate D-PHY configuration according to MIPI D-PHY specification
> + * (v1.2, Section Section 6.9 "Global Operation Timing Parameters").
> + */
> +int phy_mipi_dphy_config_validate(struct phy_configure_opts_mipi_dphy *cfg)
> +{
> + unsigned long ui;
> +
> + if (!cfg)
> + return -EINVAL;

Same here.

> + ui = DIV_ROUND_UP(NSEC_PER_SEC, cfg->hs_clk_rate);
> +
> + if (cfg->clk_miss > 60)
> + return -EINVAL;
> +
> + if (cfg->clk_post < (60 + 52 * ui))
> + return -EINVAL;
> +
> + if (cfg->clk_pre < 8)
> + return -EINVAL;
> +
> + if (cfg->clk_prepare < 38 || cfg->clk_prepare > 95)
> + return -EINVAL;
> +
> + if (cfg->clk_settle < 95 || cfg->clk_settle > 300)
> + return -EINVAL;
> +
> + if (cfg->clk_term_en > 38)
> + return -EINVAL;
> +
> + if (cfg->clk_trail < 60)
> + return -EINVAL;
> +
> + if (cfg->clk_prepare + cfg->clk_zero < 300)
> + return -EINVAL;
> +
> + if (cfg->d_term_en > 35 + 4 * ui)
> + return -EINVAL;
> +
> + if (cfg->eot > 105 + 12 * ui)
> + return -EINVAL;
> +
> + if (cfg->hs_exit < 100)
> + return -EINVAL;
> +
> + if (cfg->hs_prepare < 40 + 4 * ui ||
> + cfg->hs_prepare > 85 + 6 * ui)
> + return -EINVAL;
> +
> + if (cfg->hs_prepare + cfg->hs_zero < 145 + 10 * ui)
> + return -EINVAL;
> +
> + if ((cfg->hs_settle < 85 + 6 * ui) ||
> + (cfg->hs_settle > 145 + 10 * ui))
> + return -EINVAL;
> +
> + if (cfg->hs_skip < 40 || cfg->hs_skip > 55 + 4 * ui)
> + return -EINVAL;
> +
> + if (cfg->hs_trail < max(8 * ui, 60 + 4 * ui))
> + return -EINVAL;
> +
> + if (cfg->init < 100000)
> + return -EINVAL;
> +
> + if (cfg->lpx < 50)
> + return -EINVAL;
> +
> + if (cfg->ta_get != 5 * cfg->lpx)
> + return -EINVAL;
> +
> + if (cfg->ta_go != 4 * cfg->lpx)
> + return -EINVAL;
> +
> + if (cfg->ta_sure < cfg->lpx || cfg->ta_sure > 2 * cfg->lpx)
> + return -EINVAL;
> +
> + if (cfg->wakeup < 1000000)
> + return -EINVAL;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(phy_mipi_dphy_config_validate);
> diff --git a/include/linux/phy/phy-mipi-dphy.h
> b/include/linux/phy/phy-mipi-dphy.h index 792724145290..7656d057198f 100644
> --- a/include/linux/phy/phy-mipi-dphy.h
> +++ b/include/linux/phy/phy-mipi-dphy.h
> @@ -238,4 +238,10 @@ struct phy_configure_opts_mipi_dphy {
> /* TODO: Add other modes (burst, commands, etc) */
> #define MIPI_DPHY_MODE_VIDEO_SYNC_PULSE BIT(0)
>
> +int phy_mipi_dphy_get_default_config(unsigned long pixel_clock,
> + unsigned int bpp,
> + unsigned int lanes,
> + struct phy_configure_opts_mipi_dphy *cfg);
> +int phy_mipi_dphy_config_validate(struct phy_configure_opts_mipi_dphy
> *cfg);
> +
> #endif /* __PHY_MIPI_DPHY_H_ */


--
Regards,

Laurent Pinchart



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