Re: [Intel-gfx] [PATCH v4 14/23] drm/i915/adl_p: Tx escape clock with DSI

["Kulkarni, Vandita" <vandita.kulkarni@intel.com>]

> -----Original Message-----
> From: Roper, Matthew D <matthew.d.roper@intel.com>
> Sent: Saturday, May 15, 2021 8:40 AM
> To: intel-gfx@lists.freedesktop.org
> Cc: Kahola, Mika <mika.kahola@intel.com>; Kulkarni, Vandita
> <vandita.kulkarni@intel.com>; Taylor, Clinton A
> <clinton.a.taylor@intel.com>; Roper, Matthew D
> <matthew.d.roper@intel.com>
> Subject: [PATCH v4 14/23] drm/i915/adl_p: Tx escape clock with DSI
> 
> From: Mika Kahola <mika.kahola@intel.com>
> 
> Today when the DSI controller is paired with the Combo-PHY it uses the high-
> speed (HS) Word clock for its low power (LP) transmit PPI communication to
> the DPHY. The interface signaling only changes state at an Escape clock
> frequency (i.e. its effectively running on a virtual Tx Escape clock that is
> controlled by counters w/in the controller), but all the interface flops are
> running off the HS clock.
> 
> This has the following drawbacks:
> 
>  * It is a deviation from the PPI spec which assumes signaling is
>    running on a physical Escape clock
>  * The PV timings are over constrained (HS timed to 312.5MHz vs.
>    an Escape clock of 20MHz max)
> 
> This feature is proposing to change the LP Tx communication between the
> controller and the DPHY from a virtual Tx Escape clock to a physical clock.
> 
> To do this we need to program two "M" divisors. One for the usual
> DSI_ESC_CLK_DIV and DPHY_ESC_CLK_DIV register and one for
> MIPIO_DWORD8.
> 
> For DSI_ESC_CLK_DIV and DPHY_ESC_CLK_DIV registers the "M" is calculated
> as following
> 
> Nt = ceil(f_link/160) (theoretical word clock) Nact = max[3, Nt + (Nt + 1)%2]
> (actual word clock) M = Nact * 8
> 
> For MIPIO_DWORD8 register, the divisor "M" is calculated as following
> 
> M = (Nact - 1)/2
> 
> BSpec: 55171
> 
> Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> Signed-off-by: Clinton Taylor <Clinton.A.Taylor@intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>

Looks good to me.
Reviewed-by: Vandita Kulkarni <vandita.kulkarni@intel.com>

> ---
>  drivers/gpu/drm/i915/display/icl_dsi.c | 21 +++++++++++++++++++--
>  drivers/gpu/drm/i915/i915_reg.h        |  6 ++++++
>  2 files changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/icl_dsi.c
> b/drivers/gpu/drm/i915/display/icl_dsi.c
> index ce544e20f35c..27251b97f0c3 100644
> --- a/drivers/gpu/drm/i915/display/icl_dsi.c
> +++ b/drivers/gpu/drm/i915/display/icl_dsi.c
> @@ -363,10 +363,19 @@ static void gen11_dsi_program_esc_clk_div(struct
> intel_encoder *encoder,
>  	struct intel_dsi *intel_dsi = enc_to_intel_dsi(encoder);
>  	enum port port;
>  	int afe_clk_khz;
> -	u32 esc_clk_div_m;
> +	int theo_word_clk, act_word_clk;
> +	u32 esc_clk_div_m, esc_clk_div_m_phy;
> 
>  	afe_clk_khz = afe_clk(encoder, crtc_state);
> -	esc_clk_div_m = DIV_ROUND_UP(afe_clk_khz, DSI_MAX_ESC_CLK);
> +
> +	if (IS_ALDERLAKE_S(dev_priv) || IS_ALDERLAKE_P(dev_priv)) {
> +		theo_word_clk = DIV_ROUND_UP(afe_clk_khz, 8 *
> DSI_MAX_ESC_CLK);
> +		act_word_clk = max(3, theo_word_clk + (theo_word_clk + 1)
> % 2);
> +		esc_clk_div_m = act_word_clk * 8;
> +		esc_clk_div_m_phy = (act_word_clk - 1)/2;
> +	} else {
> +		esc_clk_div_m = DIV_ROUND_UP(afe_clk_khz,
> DSI_MAX_ESC_CLK);
> +	}
> 
>  	for_each_dsi_port(port, intel_dsi->ports) {
>  		intel_de_write(dev_priv, ICL_DSI_ESC_CLK_DIV(port), @@ -
> 379,6 +388,14 @@ static void gen11_dsi_program_esc_clk_div(struct
> intel_encoder *encoder,
>  			       esc_clk_div_m & ICL_ESC_CLK_DIV_MASK);
>  		intel_de_posting_read(dev_priv,
> ICL_DPHY_ESC_CLK_DIV(port));
>  	}
> +
> +	if (IS_ALDERLAKE_S(dev_priv) || IS_ALDERLAKE_P(dev_priv)) {
> +		for_each_dsi_port(port, intel_dsi->ports) {
> +			intel_de_write(dev_priv, ADL_MIPIO_DW(port, 8),
> +				       esc_clk_div_m_phy &
> TX_ESC_CLK_DIV_PHY);
> +			intel_de_posting_read(dev_priv,
> ADL_MIPIO_DW(port, 8));
> +		}
> +	}
>  }
> 
>  static void get_dsi_io_power_domains(struct drm_i915_private *dev_priv,
> diff --git a/drivers/gpu/drm/i915/i915_reg.h
> b/drivers/gpu/drm/i915/i915_reg.h index 0e7a2616b3cd..2906dff26868
> 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -11336,6 +11336,12 @@ enum skl_power_gate {
>  #define  ICL_ESC_CLK_DIV_SHIFT			0
>  #define DSI_MAX_ESC_CLK			20000		/* in KHz */
> 
> +#define _ADL_MIPIO_REG			0x180
> +#define ADL_MIPIO_DW(port, dw)
> 	_MMIO(_ICL_COMBOPHY(port) + _ADL_MIPIO_REG + 4 * (dw))
> +#define   TX_ESC_CLK_DIV_PHY_SEL	REGBIT(16)
> +#define   TX_ESC_CLK_DIV_PHY_MASK	REG_GENMASK(23, 16)
> +#define   TX_ESC_CLK_DIV_PHY
> 	REG_FIELD_PREP(TX_ESC_CLK_DIV_PHY_MASK, 0x7f)
> +
>  #define _DSI_CMD_FRMCTL_0		0x6b034
>  #define _DSI_CMD_FRMCTL_1		0x6b834
>  #define DSI_CMD_FRMCTL(port)		_MMIO_PORT(port,	\
> --
> 2.25.4

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