Re: [PATCH 02/12] drm/i915/bxt: Enable BXT DSI PLL

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 22 May 2015, Uma Shankar <uma.shankar@intel.com> wrote:
> From: Shashank Sharma <shashank.sharma@intel.com>
>
> This patch adds new functions for BXT clock and PLL programming.
> They are:
> 1. configure_dsi_pll for BXT.
>    This function does the basic math and generates the divider ratio
>    based on requested pixclock, and program clock registers.
> 2. enable_dsi_pll function.
>    This function programs the calculated clock values on the PLL.
> 3. intel_enable_dsi_pll
>    Wrapper function to use same code for multiple platforms. It checks the
>    platform and calls appropriate core pll enable function.
>
> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h      |   35 ++++++++++++++
>  drivers/gpu/drm/i915/intel_dsi.c     |    2 +-
>  drivers/gpu/drm/i915/intel_dsi.h     |    2 +-
>  drivers/gpu/drm/i915/intel_dsi_pll.c |   85 +++++++++++++++++++++++++++++++++-
>  4 files changed, 121 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 46ef269..b63bdce 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7352,6 +7352,41 @@ enum skl_disp_power_wells {
>  
>  /* MIPI DSI registers */
>  
> +/* BXT DSI PLL Control */

The macro name says this already, no need for the comment.

> +#define BXT_DSI_PLL_CTL                               0x161000
> +#define BXT_DSI_PLL_MASK_PVD_RATIO                   (3 << 16)

The convention is to have _SHIFT and _MASK at the end of the name.

> +#define BXT_DSI_PLL_PVD_RATIO_1                      (1<<16)

Spaces around <<. Please also add macro for _SHIFT.

> +#define BXT_DSIC_16X_BY2                             (1 << 10)
> +#define BXT_DSIC_16X_BY3                             (1 << 11)
> +#define BXT_DSIC_16X_BY4                             (3 << 10)

The convention is to shift the same amount for each alternative in a bit
field. E.g. (1 << 10), (2 << 10), (3 << 10).

> +#define BXT_DSIA_16X_BY2                             (1 << 8)
> +#define BXT_DSIA_16X_BY3                             (1 << 9)
> +#define BXT_DSIA_16X_BY4                             (3 << 8)

Same.

> +#define BXT_DSI_MASK_FREQ_SEL                        (0xF << 8)

_MASK at the end of the name, and the convention is to define _SHIFT
first, _MASK next, and the possible alternatives after that, i.e.

#define  FOO_SHIFT		16
#define  FOO_MASK		(3 << 16)
#define  FOO_A			(1 << 16)

> +#define BXT_DSI_PLL_RATIO_MAX                        0x7D
> +#define BXT_DSI_PLL_RATIO_MIN                        0x22
> +#define BXT_DSI_MASK_PLL_RATIO                       0x7F

Same as above. The mask is 8 bits, i.e. 0xff.

The convention is to have bit names shifted by two spaces. For example,

#define REGISTER_NAME					0x50000
#define   SOME_BIT					(1 << 5)

And please no empty lines between bit names, group them together.

> +#define BXT_REF_CLOCK_KHZ                            19500
> +
> +#define BXT_DSI_PLL_ENABLE                            0x46080
> +#define BXT_DSI_PLL_DO_ENABLE                         (1 << 31)
> +#define BXT_DSI_PLL_LOCKED                            (1 << 30)
> +
> +/* BXT power well control2, for driver */

The macro name says this already, no need for the comment.

> +#define BXT_PWR_WELL_CTL2                             0x45404
> +#define BXT_PWR_WELL_2_ENABLE                         (1 << 31)
> +#define BXT_PWR_WELL_2_ENABLED                        (1 << 30)
> +#define BXT_PWR_WELL_1_ENABLE                         (1 << 29)
> +#define BXT_PWR_WELL_1_ENABLED                        (1 << 28)
> +#define BXT_PWR_WELL_ENABLED  (BXT_PWR_WELL_1_ENABLED | \
> +				BXT_PWR_WELL_2_ENABLED)
> +#define GEN9_FUSE_STATUS                               0x42000
> +#define GEN9_FUSE_PG2_ENABLED                          (1 << 25)
> +#define GEN9_FUSE_PG1_ENABLED                          (1 << 26)
> +#define GEN9_FUSE_PG0_ENABLED                          (1 << 27)
> +

BXT_PWR_WELL_CTL2 and GEN9_FUSE_STATUS are not used in this series at
all, please remove them from this patch (and perhaps send them in a
separate patch).

>  #define _MIPI_PORT(port, a, c)	_PORT3(port, a, 0, c)	/* ports A and C only */
>  
>  #define _MIPIA_PORT_CTRL			(VLV_DISPLAY_BASE + 0x61190)
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index 2419929e..1927546 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -903,8 +903,8 @@ static void intel_dsi_pre_pll_enable(struct intel_encoder *encoder)
>  	DRM_DEBUG_KMS("\n");
>  
>  	intel_dsi_prepare(encoder);
> +	intel_enable_dsi_pll(encoder);
>  
> -	vlv_enable_dsi_pll(encoder);
>  }
>  
>  static enum drm_connector_status
> diff --git a/drivers/gpu/drm/i915/intel_dsi.h b/drivers/gpu/drm/i915/intel_dsi.h
> index 2784ac4..20cfcf07 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.h
> +++ b/drivers/gpu/drm/i915/intel_dsi.h
> @@ -121,7 +121,7 @@ static inline struct intel_dsi *enc_to_intel_dsi(struct drm_encoder *encoder)
>  	return container_of(encoder, struct intel_dsi, base.base);
>  }
>  
> -extern void vlv_enable_dsi_pll(struct intel_encoder *encoder);
> +extern void intel_enable_dsi_pll(struct intel_encoder *encoder);
>  extern void vlv_disable_dsi_pll(struct intel_encoder *encoder);
>  extern u32 vlv_get_dsi_pclk(struct intel_encoder *encoder, int pipe_bpp);
>  
> diff --git a/drivers/gpu/drm/i915/intel_dsi_pll.c b/drivers/gpu/drm/i915/intel_dsi_pll.c
> index 9688d99..a58f0a1 100644
> --- a/drivers/gpu/drm/i915/intel_dsi_pll.c
> +++ b/drivers/gpu/drm/i915/intel_dsi_pll.c
> @@ -237,7 +237,7 @@ static void vlv_configure_dsi_pll(struct intel_encoder *encoder)
>  	vlv_cck_write(dev_priv, CCK_REG_DSI_PLL_CONTROL, dsi_mnp.dsi_pll_ctrl);
>  }
>  
> -void vlv_enable_dsi_pll(struct intel_encoder *encoder)
> +static void vlv_enable_dsi_pll(struct intel_encoder *encoder)
>  {
>  	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
>  	u32 tmp;
> @@ -368,3 +368,86 @@ u32 vlv_get_dsi_pclk(struct intel_encoder *encoder, int pipe_bpp)
>  
>  	return pclk;
>  }
> +
> +static bool bxt_configure_dsi_pll(struct intel_encoder *encoder)
> +{
> +	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
> +	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
> +	u8 dsi_ratio;
> +	u32 dsi_clk;
> +	u32 val = 0;

Unnecessary initialization.

> +
> +	dsi_clk = dsi_clk_from_pclk(intel_dsi->pclk, intel_dsi->pixel_format,
> +			intel_dsi->lane_count);
> +
> +	/*
> +	 * From clock diagram, to get PLL ratio divider, divide double of DSI
> +	 * link rate (i.e., 2*8x=16x frequency value) by ref clock. Make sure to
> +	 * round 'up' the result
> +	 */
> +	dsi_ratio = DIV_ROUND_UP(dsi_clk * 2, BXT_REF_CLOCK_KHZ);
> +	if (dsi_ratio < BXT_DSI_PLL_RATIO_MIN ||
> +			dsi_ratio > BXT_DSI_PLL_RATIO_MAX) {
> +		DRM_ERROR("Cant get a suitable ratio from DSI PLL ratios\n");
> +		return false;
> +	}
> +
> +	/*
> +	 * Program DSI ratio and Select MIPIC and MIPIA PLL output as 8x
> +	 * Spec says both have to be programmed, even if one is not getting
> +	 * used. Configure MIPI_CLOCK_CTL dividers in modeset
> +	 */
> +	val = I915_READ(BXT_DSI_PLL_CTL);
> +	val &= ~BXT_DSI_PLL_MASK_PVD_RATIO;
> +	val &= ~BXT_DSI_MASK_FREQ_SEL;
> +	val &= ~BXT_DSI_MASK_PLL_RATIO;
> +	val |= (dsi_ratio | BXT_DSIA_16X_BY2 | BXT_DSIC_16X_BY2);
> +
> +	/* Prog PVD ratio =1 if ratio <= 50 */

I can read that from the code. The comments are for telling the reader
*why* this is being done. What's the magic 50?

> +	if (dsi_ratio <= 50) {
> +		val &= ~BXT_DSI_PLL_MASK_PVD_RATIO;
> +		val |= BXT_DSI_PLL_PVD_RATIO_1;
> +	}
> +
> +	I915_WRITE(BXT_DSI_PLL_CTL, val);

Hmm, POSTING_READ?

> +	return true;
> +}
> +
> +static void bxt_enable_dsi_pll(struct intel_encoder *encoder)
> +{
> +	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
> +	u32 val = 0;

Unnecessary initialization, the first thing you do with val is assign to
it.

> +
> +	DRM_DEBUG_KMS("\n");
> +

Perhaps you should check if DSI PLL is enabled here, and disable with a
warning if it is?

> +	/* Configure PLL vales */
> +	if (!bxt_configure_dsi_pll(encoder)) {
> +		DRM_ERROR("Configure DSI PLL failed, abort PLL enable\n");
> +		return;
> +	}
> +
> +	/* Enable DSI PLL */
> +	val = I915_READ(BXT_DSI_PLL_ENABLE);
> +	val |= BXT_DSI_PLL_DO_ENABLE;
> +	I915_WRITE(BXT_DSI_PLL_ENABLE, val);
> +
> +	/* Timeout and fail if PLL not locked */
> +	if (wait_for(I915_READ(BXT_DSI_PLL_ENABLE) & BXT_DSI_PLL_LOCKED, 1)) {
> +		DRM_ERROR("DSI PLL  not locked\n");
> +		return;
> +	}
> +
> +	DRM_DEBUG_KMS("DSI PLL locked\n");
> +}
> +
> +void intel_enable_dsi_pll(struct intel_encoder *encoder)
> +{
> +	struct drm_device *dev = encoder->base.dev;
> +
> +	if (IS_VALLEYVIEW(dev))
> +		vlv_enable_dsi_pll(encoder);
> +	else if (IS_BROXTON(dev))
> +		bxt_enable_dsi_pll(encoder);
> +	else
> +		DRM_ERROR("Invalid DSI device to pre_pll_enable\n");

Please drop all such else branches. It's already evident that having a
few of them around leads to more and more added, and there is no end to
it.

> +}
> -- 
> 1.7.9.5
>
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-- 
Jani Nikula, Intel Open Source Technology Center
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