Message-ID: <20181121132132.zeecryxvkh2wyyyg@flea>
Date:   Wed, 21 Nov 2018 14:21:32 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Sakari Ailus <sakari.ailus@....fi>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-media@...r.kernel.org,
        Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Chen-Yu Tsai <wens@...e.org>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        Krzysztof Witos <kwitos@...ence.com>,
        Rafal Ciepiela <rafalc@...ence.com>
Subject: Re: [PATCH v2 8/9] phy: Add Cadence D-PHY support

Hi Sakari,

On Mon, Nov 19, 2018 at 11:24:20PM +0200, Sakari Ailus wrote:
> Hi Maxime,
> 
> On Tue, Nov 06, 2018 at 03:54:20PM +0100, Maxime Ripard wrote:
> > Cadence has designed a D-PHY that can be used by the, currently in tree,
> > DSI bridge (DRM), CSI Transceiver and CSI Receiver (v4l2) drivers.
> > 
> > Only the DSI driver has an ad-hoc driver for that phy at the moment, while
> > the v4l2 drivers are completely missing any phy support. In order to make
> > that phy support available to all these drivers, without having to
> > duplicate that code three times, let's create a generic phy framework
> > driver.
> > 
> > Signed-off-by: Maxime Ripard <maxime.ripard@...tlin.com>
> > ---
> >  Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt |  21 +-
> >  Documentation/devicetree/bindings/phy/cdns,dphy.txt           |  20 +-
> 
> Coould you split out the DT binding changes into a separate patch?

Will do.

> >  drivers/phy/cadence/Kconfig                                   |  13 +-
> >  drivers/phy/cadence/Makefile                                  |   1 +-
> >  drivers/phy/cadence/cdns-dphy.c                               | 459 +++++++-
> >  5 files changed, 492 insertions(+), 22 deletions(-)
> >  create mode 100644 Documentation/devicetree/bindings/phy/cdns,dphy.txt
> >  create mode 100644 drivers/phy/cadence/cdns-dphy.c
> > 
> > diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt b/Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt
> > index f5725bb6c61c..525a4bfd8634 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt
> > +++ b/Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt
> > @@ -31,28 +31,7 @@ Required subnodes:
> >  - one subnode per DSI device connected on the DSI bus. Each DSI device should
> >    contain a reg property encoding its virtual channel.
> >  
> > -Cadence DPHY
> > -============
> > -
> > -Cadence DPHY block.
> > -
> > -Required properties:
> > -- compatible: should be set to "cdns,dphy".
> > -- reg: physical base address and length of the DPHY registers.
> > -- clocks: DPHY reference clocks.
> > -- clock-names: must contain "psm" and "pll_ref".
> > -- #phy-cells: must be set to 0.
> > -
> > -
> >  Example:
> > -	dphy0: dphy@...e0000{
> > -		compatible = "cdns,dphy";
> > -		reg = <0x0 0xfd0e0000 0x0 0x1000>;
> > -		clocks = <&psm_clk>, <&pll_ref_clk>;
> > -		clock-names = "psm", "pll_ref";
> > -		#phy-cells = <0>;
> > -	};
> > -
> >  	dsi0: dsi@...c0000 {
> >  		compatible = "cdns,dsi";
> >  		reg = <0x0 0xfd0c0000 0x0 0x1000>;
> > diff --git a/Documentation/devicetree/bindings/phy/cdns,dphy.txt b/Documentation/devicetree/bindings/phy/cdns,dphy.txt
> > new file mode 100644
> > index 000000000000..1095bc4e72d9
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/phy/cdns,dphy.txt
> > @@ -0,0 +1,20 @@
> > +Cadence DPHY
> > +============
> > +
> > +Cadence DPHY block.
> > +
> > +Required properties:
> > +- compatible: should be set to "cdns,dphy".
> > +- reg: physical base address and length of the DPHY registers.
> > +- clocks: DPHY reference clocks.
> > +- clock-names: must contain "psm" and "pll_ref".
> > +- #phy-cells: must be set to 0.
> > +
> > +Example:
> > +	dphy0: dphy@...e0000{
> > +		compatible = "cdns,dphy";
> > +		reg = <0x0 0xfd0e0000 0x0 0x1000>;
> > +		clocks = <&psm_clk>, <&pll_ref_clk>;
> > +		clock-names = "psm", "pll_ref";
> > +		#phy-cells = <0>;
> > +	};
> > diff --git a/drivers/phy/cadence/Kconfig b/drivers/phy/cadence/Kconfig
> > index 57fff7de4031..240effa81046 100644
> > --- a/drivers/phy/cadence/Kconfig
> > +++ b/drivers/phy/cadence/Kconfig
> > @@ -1,6 +1,7 @@
> >  #
> > -# Phy driver for Cadence MHDP DisplayPort controller
> > +# Phy drivers for Cadence IPs
> >  #
> > +
> >  config PHY_CADENCE_DP
> >  	tristate "Cadence MHDP DisplayPort PHY driver"
> >  	depends on OF
> > @@ -8,3 +9,13 @@ config PHY_CADENCE_DP
> >  	select GENERIC_PHY
> >  	help
> >  	  Support for Cadence MHDP DisplayPort PHY.
> > +
> > +config PHY_CADENCE_DPHY
> > +	tristate "Cadence D-PHY Support"
> > +	depends on HAS_IOMEM && OF
> > +	select GENERIC_PHY
> > +	select GENERIC_PHY_MIPI_DPHY
> > +	help
> > +	  Choose this option if you have a Cadence D-PHY in your
> > +	  system. If M is selected, the module will be called
> > +	  cdns-csi.
> > diff --git a/drivers/phy/cadence/Makefile b/drivers/phy/cadence/Makefile
> > index e5b0a11cf28a..64cb9ea66ceb 100644
> > --- a/drivers/phy/cadence/Makefile
> > +++ b/drivers/phy/cadence/Makefile
> > @@ -1 +1,2 @@
> >  obj-$(CONFIG_PHY_CADENCE_DP)	+= phy-cadence-dp.o
> > +obj-$(CONFIG_PHY_CADENCE_DPHY)	+= cdns-dphy.o
> > diff --git a/drivers/phy/cadence/cdns-dphy.c b/drivers/phy/cadence/cdns-dphy.c
> > new file mode 100644
> > index 000000000000..a398b401e5d3
> > --- /dev/null
> > +++ b/drivers/phy/cadence/cdns-dphy.c
> > @@ -0,0 +1,459 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright: 2017-2018 Cadence Design Systems, Inc.
> > + */
> > +
> > +#include <linux/bitops.h>
> > +#include <linux/clk.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/of_address.h>
> > +#include <linux/of_device.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/reset.h>
> > +
> > +#include <linux/phy/phy.h>
> > +#include <linux/phy/phy-mipi-dphy.h>
> > +
> > +#define REG_WAKEUP_TIME_NS		800
> > +#define DPHY_PLL_RATE_HZ		108000000
> > +
> > +/* DPHY registers */
> > +#define DPHY_PMA_CMN(reg)		(reg)
> > +#define DPHY_PMA_LCLK(reg)		(0x100 + (reg))
> > +#define DPHY_PMA_LDATA(lane, reg)	(0x200 + ((lane) * 0x100) + (reg))
> > +#define DPHY_PMA_RCLK(reg)		(0x600 + (reg))
> > +#define DPHY_PMA_RDATA(lane, reg)	(0x700 + ((lane) * 0x100) + (reg))
> > +#define DPHY_PCS(reg)			(0xb00 + (reg))
> > +
> > +#define DPHY_CMN_SSM			DPHY_PMA_CMN(0x20)
> > +#define DPHY_CMN_SSM_EN			BIT(0)
> > +#define DPHY_CMN_TX_MODE_EN		BIT(9)
> > +
> > +#define DPHY_CMN_PWM			DPHY_PMA_CMN(0x40)
> > +#define DPHY_CMN_PWM_DIV(x)		((x) << 20)
> > +#define DPHY_CMN_PWM_LOW(x)		((x) << 10)
> > +#define DPHY_CMN_PWM_HIGH(x)		(x)
> > +
> > +#define DPHY_CMN_FBDIV			DPHY_PMA_CMN(0x4c)
> > +#define DPHY_CMN_FBDIV_VAL(low, high)	(((high) << 11) | ((low) << 22))
> > +#define DPHY_CMN_FBDIV_FROM_REG		(BIT(10) | BIT(21))
> > +
> > +#define DPHY_CMN_OPIPDIV		DPHY_PMA_CMN(0x50)
> > +#define DPHY_CMN_IPDIV_FROM_REG		BIT(0)
> > +#define DPHY_CMN_IPDIV(x)		((x) << 1)
> > +#define DPHY_CMN_OPDIV_FROM_REG		BIT(6)
> > +#define DPHY_CMN_OPDIV(x)		((x) << 7)
> > +
> > +#define DPHY_PSM_CFG			DPHY_PCS(0x4)
> > +#define DPHY_PSM_CFG_FROM_REG		BIT(0)
> > +#define DPHY_PSM_CLK_DIV(x)		((x) << 1)
> > +
> > +#define DSI_HBP_FRAME_OVERHEAD		12
> > +#define DSI_HSA_FRAME_OVERHEAD		14
> > +#define DSI_HFP_FRAME_OVERHEAD		6
> > +#define DSI_HSS_VSS_VSE_FRAME_OVERHEAD	4
> > +#define DSI_BLANKING_FRAME_OVERHEAD	6
> > +#define DSI_NULL_FRAME_OVERHEAD		6
> > +#define DSI_EOT_PKT_SIZE		4
> > +
> > +struct cdns_dphy_cfg {
> > +	u8 pll_ipdiv;
> > +	u8 pll_opdiv;
> > +	u16 pll_fbdiv;
> > +	unsigned int nlanes;
> > +};
> > +
> > +enum cdns_dphy_clk_lane_cfg {
> > +	DPHY_CLK_CFG_LEFT_DRIVES_ALL = 0,
> > +	DPHY_CLK_CFG_LEFT_DRIVES_RIGHT = 1,
> > +	DPHY_CLK_CFG_LEFT_DRIVES_LEFT = 2,
> > +	DPHY_CLK_CFG_RIGHT_DRIVES_ALL = 3,
> > +};
> > +
> > +struct cdns_dphy;
> > +struct cdns_dphy_ops {
> > +	int (*probe)(struct cdns_dphy *dphy);
> > +	void (*remove)(struct cdns_dphy *dphy);
> > +	void (*set_psm_div)(struct cdns_dphy *dphy, u8 div);
> > +	void (*set_clk_lane_cfg)(struct cdns_dphy *dphy,
> > +				 enum cdns_dphy_clk_lane_cfg cfg);
> > +	void (*set_pll_cfg)(struct cdns_dphy *dphy,
> > +			    const struct cdns_dphy_cfg *cfg);
> > +	unsigned long (*get_wakeup_time_ns)(struct cdns_dphy *dphy);
> > +};
> > +
> > +struct cdns_dphy {
> > +	struct cdns_dphy_cfg cfg;
> > +	void __iomem *regs;
> > +	struct clk *psm_clk;
> > +	struct clk *pll_ref_clk;
> > +	const struct cdns_dphy_ops *ops;
> > +	struct phy *phy;
> > +};
> > +
> > +static int cdns_dsi_get_dphy_pll_cfg(struct cdns_dphy *dphy,
> > +				     struct cdns_dphy_cfg *cfg,
> > +				     struct phy_configure_opts_mipi_dphy *opts,
> > +				     unsigned int *dsi_hfp_ext)
> > +{
> > +	u64 dlane_bps, dlane_bps_max, fbdiv, fbdiv_max, adj_dsi_htotal;
> > +	unsigned long pll_ref_hz = clk_get_rate(dphy->pll_ref_clk);
> > +
> > +	memset(cfg, 0, sizeof(*cfg));
> > +
> > +	if (pll_ref_hz < 9600000 || pll_ref_hz >= 150000000)
> > +		return -EINVAL;
> > +	else if (pll_ref_hz < 19200000)
> > +		cfg->pll_ipdiv = 1;
> > +	else if (pll_ref_hz < 38400000)
> > +		cfg->pll_ipdiv = 2;
> > +	else if (pll_ref_hz < 76800000)
> > +		cfg->pll_ipdiv = 4;
> > +	else
> > +		cfg->pll_ipdiv = 8;
> > +
> > +	dlane_bps = opts->hs_clk_rate;
> > +
> > +	if (dlane_bps > 2500000000UL || dlane_bps < 160000000UL)
> > +		return -EINVAL;
> > +	else if (dlane_bps >= 1250000000)
> > +		cfg->pll_opdiv = 1;
> > +	else if (dlane_bps >= 630000000)
> > +		cfg->pll_opdiv = 2;
> > +	else if (dlane_bps >= 320000000)
> > +		cfg->pll_opdiv = 4;
> > +	else if (dlane_bps >= 160000000)
> > +		cfg->pll_opdiv = 8;
> > +
> > +	/*
> > +	 * Allow a deviation of 0.2% on the per-lane data rate to try to
> > +	 * recover a potential mismatch between DPI and PPI clks.
> > +	 */
> > +	dlane_bps_max = dlane_bps + DIV_ROUND_DOWN_ULL(dlane_bps, 500);
> > +	fbdiv_max = DIV_ROUND_DOWN_ULL(dlane_bps_max * 2 *
> > +				       cfg->pll_opdiv * cfg->pll_ipdiv,
> > +				       pll_ref_hz);
> > +	fbdiv = DIV_ROUND_UP_ULL(dlane_bps * 2 * cfg->pll_opdiv *
> > +				 cfg->pll_ipdiv,
> > +				 pll_ref_hz);
> > +
> > +	/*
> > +	 * Iterate over all acceptable fbdiv and try to find an adjusted DSI
> > +	 * htotal length providing an exact match.
> > +	 *
> > +	 * Note that we could do something even trickier by relying on the fact
> > +	 * that a new line is not necessarily aligned on a lane boundary, so,
> > +	 * by making adj_dsi_htotal non aligned on a dsi_lanes we can improve a
> > +	 * bit the precision. With this, the step would be
> > +	 *
> > +	 *	pll_ref_hz / (2 * opdiv * ipdiv * nlanes)
> > +	 *
> > +	 * instead of
> > +	 *
> > +	 *	pll_ref_hz / (2 * opdiv * ipdiv)
> > +	 *
> > +	 * The drawback of this approach is that we would need to make sure the
> > +	 * number or lines is a multiple of the realignment periodicity which is
> > +	 * a function of the number of lanes and the original misalignment. For
> > +	 * example, for NLANES = 4 and HTOTAL % NLANES = 3, it takes 4 lines
> > +	 * to realign on a lane:
> > +	 * LINE 0: expected number of bytes, starts emitting first byte of
> > +	 *	   LINE 1 on LANE 3
> > +	 * LINE 1: expected number of bytes, starts emitting first 2 bytes of
> > +	 *	   LINE 2 on LANES 2 and 3
> > +	 * LINE 2: expected number of bytes, starts emitting first 3 bytes of
> > +	 *	   of LINE 3 on LANES 1, 2 and 3
> > +	 * LINE 3: one byte less, now things are realigned on LANE 0 for LINE 4
> > +	 *
> > +	 * I figured this extra complexity was not worth the benefit, but if
> > +	 * someone really has unfixable mismatch, that would be something to
> > +	 * investigate.
> > +	 */
> > +	for (; fbdiv <= fbdiv_max; fbdiv++) {
> > +		u32 rem;
> > +
> > +		/*
> > +		 * Do the division in 2 steps to avoid an overflow on the
> > +		 * divider.
> > +		 */
> > +		rem = do_div(adj_dsi_htotal, opts->hs_clk_rate);
> 
> Hmm. I don't see adj_dsi_htotal being set anywhere. I suppose that can't be
> intended.
> 
> > +		if (rem)
> > +			continue;
> > +
> > +		rem = do_div(adj_dsi_htotal,
> > +			     cfg->pll_opdiv * cfg->pll_ipdiv * 2 * 8);
> > +		if (rem)
> > +			continue;
> 
> Is fbdiv supposed to be used in the formula somewhere?

Hmmm, right. Something's fishy here.

> > +static int cdns_dphy_exit(struct phy *phy)
> > +{
> > +	struct cdns_dphy *dphy = phy_get_drvdata(phy);
> > +
> > +	clk_disable_unprepare(dphy->pll_ref_clk);
> > +	clk_disable_unprepare(dphy->psm_clk);
> 
> Wouldn't this belong to power_off() (and enabling the clocks to
> power_on())?

Yep, it would make more sense.

> > +
> > +	return 0;
> > +}
> > +
> > +static struct phy_ops cdns_dphy_ops = {
> 
> const
> 
> > +	.configure	= cdns_dphy_configure,
> > +	.validate	= cdns_dphy_validate,
> > +	.power_on	= cdns_dphy_power_on,
> 
> How does it stop? Or does it? :-)

It's only been run in a simulator so far, so I'm not sure "turn on"
and "turn off" are concepts that can apply to this driver at this
point :)

> > +	.init		= cdns_dphy_init,
> 
> It'd be nice to maintain the order the same as in here (unless there are
> reasons to do otherwise, of course).

What do you mean?

> > +		ret = dphy->ops->probe(dphy);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	dphy->phy = devm_phy_create(&pdev->dev, NULL, &cdns_dphy_ops);
> > +	if (IS_ERR(dphy->phy)) {
> > +		dev_err(&pdev->dev, "failed to create PHY\n");
> > +		return PTR_ERR(dphy->phy);
> 
> Would it be appropriate to call the remove callback here?

Definitely, I'll add it.

Thanks!
Maxime

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

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