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SubjectRe: [PATCH 04/10] phy: dphy: Add configuration helpers
On Wed, Sep 05, 2018 at 04:46:05PM +0300, Laurent Pinchart wrote:
> 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 ?

Probably not :)

> > 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 ?

I will. This was taken from the Tegra DSI driver, so I'm not sure what
these are exactly, but that should be addressed.

> > + */
> > +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 ?

It avoids a kernel panic and it's not in a hot patch, so I'd say yes?

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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