Re: [PATCH 02/14] phy: allwinner: phy-sun6i-mipi-dphy: Support D-PHY Rx mode for MIPI CSI-2

[Paul Kocialkowski]

Hi,

On Mon 26 Oct 20, 16:38, Maxime Ripard wrote:
> On Fri, Oct 23, 2020 at 07:45:34PM +0200, Paul Kocialkowski wrote:
> > The Allwinner A31 D-PHY supports both Rx and Tx modes. While the latter
> > is already supported and used for MIPI DSI this adds support for the
> > former, to be used with MIPI CSI-2.
> > 
> > This implementation is inspired by the Allwinner BSP implementation.
> 
> Mentionning which BSP you took this from would be helpful

Sure! It's from the Github repo linked from https://linux-sunxi.org/V3s.
Would you like that I mention this URL explicitly or would it be enough to
mention "Allwinner's V3s Linux SDK" as they seem to call it?

> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@xxxxxxxxxxx>
> > ---
> >  drivers/phy/allwinner/phy-sun6i-mipi-dphy.c | 164 +++++++++++++++++++-
> >  1 file changed, 160 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/phy/allwinner/phy-sun6i-mipi-dphy.c b/drivers/phy/allwinner/phy-sun6i-mipi-dphy.c
> > index 1fa761ba6cbb..8bcd4bb79f60 100644
> > --- a/drivers/phy/allwinner/phy-sun6i-mipi-dphy.c
> > +++ b/drivers/phy/allwinner/phy-sun6i-mipi-dphy.c
> > @@ -24,6 +24,14 @@
> >  #define SUN6I_DPHY_TX_CTL_REG		0x04
> >  #define SUN6I_DPHY_TX_CTL_HS_TX_CLK_CONT	BIT(28)
> >  
> > +#define SUN6I_DPHY_RX_CTL_REG		0x08
> > +#define SUN6I_DPHY_RX_CTL_EN_DBC	BIT(31)
> > +#define SUN6I_DPHY_RX_CTL_RX_CLK_FORCE	BIT(24)
> > +#define SUN6I_DPHY_RX_CTL_RX_D3_FORCE	BIT(23)
> > +#define SUN6I_DPHY_RX_CTL_RX_D2_FORCE	BIT(22)
> > +#define SUN6I_DPHY_RX_CTL_RX_D1_FORCE	BIT(21)
> > +#define SUN6I_DPHY_RX_CTL_RX_D0_FORCE	BIT(20)
> > +
> 
> It's hard to tell from the diff, but it looks like you aligned the
> BIT(..) with the register?

That's correct, yes.

> If so, you should follow the what the rest of this driver (ie, one more
> indentation for register values).

I'll fix it in the next revision!

> >  #define SUN6I_DPHY_TX_TIME0_REG		0x10
> >  #define SUN6I_DPHY_TX_TIME0_HS_TRAIL(n)		(((n) & 0xff) << 24)
> >  #define SUN6I_DPHY_TX_TIME0_HS_PREPARE(n)	(((n) & 0xff) << 16)
> > @@ -44,12 +52,29 @@
> >  #define SUN6I_DPHY_TX_TIME4_HS_TX_ANA1(n)	(((n) & 0xff) << 8)
> >  #define SUN6I_DPHY_TX_TIME4_HS_TX_ANA0(n)	((n) & 0xff)
> >  
> > +#define SUN6I_DPHY_RX_TIME0_REG		0x30
> > +#define SUN6I_DPHY_RX_TIME0_HS_RX_SYNC(n)	(((n) & 0xff) << 24)
> > +#define SUN6I_DPHY_RX_TIME0_HS_RX_CLK_MISS(n)	(((n) & 0xff) << 16)
> > +#define SUN6I_DPHY_RX_TIME0_LP_RX(n)		(((n) & 0xff) << 8)
> > +
> > +#define SUN6I_DPHY_RX_TIME1_REG		0x34
> > +#define SUN6I_DPHY_RX_TIME1_RX_DLY(n)		(((n) & 0xfff) << 20)
> > +#define SUN6I_DPHY_RX_TIME1_LP_RX_ULPS_WP(n)	((n) & 0xfffff)
> > +
> > +#define SUN6I_DPHY_RX_TIME2_REG		0x38
> > +#define SUN6I_DPHY_RX_TIME2_HS_RX_ANA1(n)	(((n) & 0xff) << 8)
> > +#define SUN6I_DPHY_RX_TIME2_HS_RX_ANA0(n)	((n) & 0xff)
> > +
> > +#define SUN6I_DPHY_RX_TIME3_REG		0x40
> > +#define SUN6I_DPHY_RX_TIME3_LPRST_DLY(n)	(((n) & 0xffff) << 16)
> > +
> >  #define SUN6I_DPHY_ANA0_REG		0x4c
> >  #define SUN6I_DPHY_ANA0_REG_PWS			BIT(31)
> >  #define SUN6I_DPHY_ANA0_REG_DMPC		BIT(28)
> >  #define SUN6I_DPHY_ANA0_REG_DMPD(n)		(((n) & 0xf) << 24)
> >  #define SUN6I_DPHY_ANA0_REG_SLV(n)		(((n) & 7) << 12)
> >  #define SUN6I_DPHY_ANA0_REG_DEN(n)		(((n) & 0xf) << 8)
> > +#define SUN6I_DPHY_ANA0_REG_SFB(n)		(((n) & 3) << 2)
> >  
> >  #define SUN6I_DPHY_ANA1_REG		0x50
> >  #define SUN6I_DPHY_ANA1_REG_VTTMODE		BIT(31)
> > @@ -92,6 +117,8 @@ struct sun6i_dphy {
> >  
> >  	struct phy				*phy;
> >  	struct phy_configure_opts_mipi_dphy	config;
> > +
> > +	int					submode;
> >  };
> >  
> >  static int sun6i_dphy_init(struct phy *phy)
> > @@ -105,6 +132,18 @@ static int sun6i_dphy_init(struct phy *phy)
> >  	return 0;
> >  }
> >  
> > +static int sun6i_dphy_set_mode(struct phy *phy, enum phy_mode mode, int submode)
> > +{
> > +	struct sun6i_dphy *dphy = phy_get_drvdata(phy);
> > +
> > +	if (mode != PHY_MODE_MIPI_DPHY)
> > +		return -EINVAL;
> > +
> > +	dphy->submode = submode;
> > +
> > +	return 0;
> > +}
> > +
> >  static int sun6i_dphy_configure(struct phy *phy, union phy_configure_opts *opts)
> >  {
> >  	struct sun6i_dphy *dphy = phy_get_drvdata(phy);
> > @@ -119,9 +158,8 @@ static int sun6i_dphy_configure(struct phy *phy, union phy_configure_opts *opts)
> >  	return 0;
> >  }
> >  
> > -static int sun6i_dphy_power_on(struct phy *phy)
> > +static int sun6i_dphy_tx_power_on(struct sun6i_dphy *dphy)
> >  {
> > -	struct sun6i_dphy *dphy = phy_get_drvdata(phy);
> >  	u8 lanes_mask = GENMASK(dphy->config.lanes - 1, 0);
> >  
> >  	regmap_write(dphy->regs, SUN6I_DPHY_TX_CTL_REG,
> > @@ -211,12 +249,129 @@ static int sun6i_dphy_power_on(struct phy *phy)
> >  	return 0;
> >  }
> >  
> > +static int sun6i_dphy_rx_power_on(struct sun6i_dphy *dphy)
> > +{
> > +	/* Physical clock rate is actually half of symbol rate with DDR. */
> > +	unsigned long mipi_symbol_rate = dphy->config.hs_clk_rate;
> > +	unsigned long dphy_clk_rate;
> > +	unsigned int rx_dly;
> > +	unsigned int lprst_dly;
> > +	u32 value;
> > +
> > +	dphy_clk_rate = clk_get_rate(dphy->mod_clk);
> > +	if (!dphy_clk_rate)
> > +		return -1;
> 
> Returning -1 is weird here?

What do you think would be a more appropriate error code to return?
It looks like some other drivers return -EINVAL when that happens (but many
don't do the check).

> > +
> > +	/* Hardcoded timing parameters from the Allwinner BSP. */
> > +	regmap_write(dphy->regs, SUN6I_DPHY_RX_TIME0_REG,
> > +		     SUN6I_DPHY_RX_TIME0_HS_RX_SYNC(255) |
> > +		     SUN6I_DPHY_RX_TIME0_HS_RX_CLK_MISS(255) |
> > +		     SUN6I_DPHY_RX_TIME0_LP_RX(255));
> > +
> > +	/*
> > +	 * Formula from the Allwinner BSP, with hardcoded coefficients
> > +	 * (probably internal divider/multiplier).
> > +	 */
> > +	rx_dly = 8 * (unsigned int)(dphy_clk_rate / (mipi_symbol_rate / 8));
> > +
> > +	/*
> > +	 * The Allwinner BSP has an alternative formula for LP_RX_ULPS_WP:
> > +	 * lp_ulps_wp_cnt = lp_ulps_wp_ms * lp_clk / 1000
> > +	 * but does not use it and hardcodes 255 instead.
> > +	 */
> > +	regmap_write(dphy->regs, SUN6I_DPHY_RX_TIME1_REG,
> > +		     SUN6I_DPHY_RX_TIME1_RX_DLY(rx_dly) |
> > +		     SUN6I_DPHY_RX_TIME1_LP_RX_ULPS_WP(255));
> > +
> > +	/* HS_RX_ANA0 value is hardcoded in the Allwinner BSP. */
> > +	regmap_write(dphy->regs, SUN6I_DPHY_RX_TIME2_REG,
> > +		     SUN6I_DPHY_RX_TIME2_HS_RX_ANA0(4));
> > +
> > +	/*
> > +	 * Formula from the Allwinner BSP, with hardcoded coefficients
> > +	 * (probably internal divider/multiplier).
> > +	 */
> > +	lprst_dly = 4 * (unsigned int)(dphy_clk_rate / (mipi_symbol_rate / 2));
> > +
> > +	regmap_write(dphy->regs, SUN6I_DPHY_RX_TIME3_REG,
> > +		     SUN6I_DPHY_RX_TIME3_LPRST_DLY(lprst_dly));
> > +
> > +	/* Analog parameters are hardcoded in the Allwinner BSP. */
> > +	regmap_write(dphy->regs, SUN6I_DPHY_ANA0_REG,
> > +		     SUN6I_DPHY_ANA0_REG_PWS |
> > +		     SUN6I_DPHY_ANA0_REG_SLV(7) |
> > +		     SUN6I_DPHY_ANA0_REG_SFB(2));
> > +
> > +	regmap_write(dphy->regs, SUN6I_DPHY_ANA1_REG,
> > +		     SUN6I_DPHY_ANA1_REG_SVTT(4));
> > +
> > +	regmap_write(dphy->regs, SUN6I_DPHY_ANA4_REG,
> > +		     SUN6I_DPHY_ANA4_REG_DMPLVC |
> > +		     SUN6I_DPHY_ANA4_REG_DMPLVD(1));
> > +
> > +	regmap_write(dphy->regs, SUN6I_DPHY_ANA2_REG,
> > +		     SUN6I_DPHY_ANA2_REG_ENIB);
> > +
> > +	regmap_write(dphy->regs, SUN6I_DPHY_ANA3_REG,
> > +		     SUN6I_DPHY_ANA3_EN_LDOR |
> > +		     SUN6I_DPHY_ANA3_EN_LDOC |
> > +		     SUN6I_DPHY_ANA3_EN_LDOD);
> > +
> > +	/*
> > +	 * Delay comes from the Allwinner BSP, likely for internal regulator
> > +	 * ramp-up.
> > +	 */
> > +	udelay(3);
> > +
> > +	value = SUN6I_DPHY_RX_CTL_EN_DBC | SUN6I_DPHY_RX_CTL_RX_CLK_FORCE;
> > +
> > +	/*
> > +	 * Rx data lane force-enable bits are used as regular RX enable by the
> > +	 * Allwinner BSP.
> > +	 */
> > +	if (dphy->config.lanes >= 1)
> > +		value |= SUN6I_DPHY_RX_CTL_RX_D0_FORCE;
> > +	if (dphy->config.lanes >= 2)
> > +		value |= SUN6I_DPHY_RX_CTL_RX_D1_FORCE;
> > +	if (dphy->config.lanes >= 3)
> > +		value |= SUN6I_DPHY_RX_CTL_RX_D2_FORCE;
> > +	if (dphy->config.lanes == 4)
> > +		value |= SUN6I_DPHY_RX_CTL_RX_D3_FORCE;
> > +
> > +	regmap_write(dphy->regs, SUN6I_DPHY_RX_CTL_REG, value);
> > +
> > +	regmap_write(dphy->regs, SUN6I_DPHY_GCTL_REG,
> > +		     SUN6I_DPHY_GCTL_LANE_NUM(dphy->config.lanes) |
> > +		     SUN6I_DPHY_GCTL_EN);
> > +
> > +	return 0;
> > +}
> > +
> > +static int sun6i_dphy_power_on(struct phy *phy)
> > +{
> > +	struct sun6i_dphy *dphy = phy_get_drvdata(phy);
> > +
> > +	switch (dphy->submode) {
> > +	case PHY_MIPI_DPHY_SUBMODE_TX:
> > +		return sun6i_dphy_tx_power_on(dphy);
> > +	case PHY_MIPI_DPHY_SUBMODE_RX:
> > +		return sun6i_dphy_rx_power_on(dphy);
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> 
> Can one call power_on before set_mode?

I didn't find anything indicating this is illegal. What would happen here is
that the D-PHY would be configured to PHY_MIPI_DPHY_SUBMODE_TX (submode == 0)
at power-on if set_mode is not called before.

I think it's fair to expect that it's too late to change the mode once the PHY
was powered on. Maybe we should return -EBUSY on set_mode when power on was
already requested?

> >  static int sun6i_dphy_power_off(struct phy *phy)
> >  {
> >  	struct sun6i_dphy *dphy = phy_get_drvdata(phy);
> >  
> > -	regmap_update_bits(dphy->regs, SUN6I_DPHY_ANA1_REG,
> > -			   SUN6I_DPHY_ANA1_REG_VTTMODE, 0);
> > +	regmap_write(dphy->regs, SUN6I_DPHY_GCTL_REG, 0);
> > +
> > +	regmap_write(dphy->regs, SUN6I_DPHY_ANA0_REG, 0);
> > +	regmap_write(dphy->regs, SUN6I_DPHY_ANA1_REG, 0);
> 
> This looks like a change that should be mentioned (or in a separate
> patch).

Right, this is a general change that applies to both Tx and Rx to cut-off the
internal regulators. It's not directly related to this change so I think making
it a preliminary patch would make sense.

Thanks for the review!

Paul


-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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