Re: [BXT MIPI PATCH v2 07/13] drm/i915/bxt: Program Tx Rx and Dphy clocks

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

On Sun, 26 Jul 2015, Uma Shankar <uma.shankar@intel.com> wrote:
> From: Shashank Sharma <shashank.sharma@intel.com>
>
> BXT DSI clocks are different than previous platforms. So adding a
> new function to program following clocks and dividers:
> 1. Program variable divider to generate input to Tx clock divider
>    (Output value must be < 39.5Mhz)
> 2. Select divide by 2 option to get < 20Mhz for Tx clock
> 3. Program 8by3 divider to generate Rx clock
>
> v2: Fixed Jani's review comments. Adjusted the Macro defintion as
>     per convention. Simplified the logic for bit definitions for
>     MIPI PORT A and PORT C in same registers.
>
> 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      |   40 +++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_dsi_pll.c |   41 ++++++++++++++++++++++++++++++++++
>  2 files changed, 81 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 7559062..310afd4 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7445,6 +7445,46 @@ enum skl_disp_power_wells {
>  
>  #define _MIPI_PORT(port, a, c)	_PORT3(port, a, 0, c)	/* ports A and C only */
>  
> +/* BXT MIPI clock controls */
> +#define BXT_MAX_VAR_OUTPUT_KHZ			39500
> +
> +#define BXT_MIPI_CLOCK_CTL			0x46090
> +#define  BXT_MIPI_DIV_SHIFT			16
> +/* Var clock divider to generate TX source. Result must be < 39.5 M */
> +#define  BXT_MIPI1_ESCLK_VAR_DIV_MASK		(0x3F << 26)
> +#define  BXT_MIPI2_ESCLK_VAR_DIV_MASK		(0x3F << 10)
> +#define  BXT_MIPI_ESCLK_VAR_DIV_MASK(port)	\
> +		(0x3F << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 10))
> +#define  BXT_MIPI_ESCLK_VAR_DIV(port, val)            \
> +		(val << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 10))
> +/* TX control divider to select actual TX clock output from (8x/var) */
> +#define  BXT_MIPI1_TX_ESCLK_FIXDIV_MASK		(3 << 21)
> +#define  BXT_MIPI2_TX_ESCLK_FIXDIV_MASK		(3 << 5)
> +#define  BXT_MIPI_TX_ESCLK_FIXDIV_MASK(port)	\
> +		(3 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 5))
> +#define  BXT_MIPI_TX_ESCLK_8XDIV_BY2(port)	\
> +		(0x0 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 5))
> +#define  BXT_MIPI_TX_ESCLK_8XDIV_BY4(port)	\
> +		(0x1 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 5))
> +#define  BXT_MIPI_TX_ESCLK_8XDIV_BY8(port)	\
> +		(0x2 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 5))
> +/* RX control divider to select actual RX clock output from 8x*/
> +#define  BXT_MIPI1_RX_ESCLK_FIXDIV_MASK		(3 << 19)
> +#define  BXT_MIPI2_RX_ESCLK_FIXDIV_MASK		(3 << 3)
> +#define  BXT_MIPI_RX_ESCLK_FIXDIV_MASK(port)	\
> +		(3 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 3))
> +#define  BXT_MIPI_RX_ESCLK_8X_BY2(port)	\
> +		(1 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 3))
> +#define  BXT_MIPI_RX_ESCLK_8X_BY3(port)	\
> +		(2 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 3))
> +#define  BXT_MIPI_RX_ESCLK_8X_BY4(port)	\
> +		(3 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT + 3))
> +/* BXT: Always prog DPHY dividers to 00 */
> +#define  BXT_MIPI_1_DPHY_DIVIDER_MASK		(3 << 16)
> +#define  BXT_MIPI_2_DPHY_DIVIDER_MASK		(3 << 0)
> +#define  BXT_MIPI_DPHY_DIVIDER_MASK(port)	\
> +		(3 << ((port == PORT_A) * BXT_MIPI_DIV_SHIFT))

Meh. Please define the shifts and masks for all fields, and if you want
to have macros with port argument, please use _MIPI_PORT for defining
them.

For example,

#define  _BXT_MIPI1_TX_ESCLK_FIXDIV_MASK		(3 << 21)
#define  _BXT_MIPI2_TX_ESCLK_FIXDIV_MASK		(3 << 5)
#define  BXT_MIPI_TX_ESCLK_FIXDIV_MASK(port) \
	_MIPI_PORT(port, _BXT_MIPI1_TX_ESCLK_FIXDIV_MASK, _BXT_MIPI2_TX_ESCLK_FIXDIV_MASK)


> +
>  /* BXT MIPI mode configure */
>  #define  _BXT_MIPIA_TRANS_HACTIVE			0x6B0F8
>  #define  _BXT_MIPIC_TRANS_HACTIVE			0x6B8F8
> diff --git a/drivers/gpu/drm/i915/intel_dsi_pll.c b/drivers/gpu/drm/i915/intel_dsi_pll.c
> index f335e6c..0b74399 100644
> --- a/drivers/gpu/drm/i915/intel_dsi_pll.c
> +++ b/drivers/gpu/drm/i915/intel_dsi_pll.c
> @@ -384,6 +384,41 @@ u32 vlv_get_dsi_pclk(struct intel_encoder *encoder, int pipe_bpp)
>  	return pclk;
>  }
>  
> +/* Program BXT Mipi clocks and dividers */
> +static void bxt_dsi_program_clocks(struct drm_device *dev, enum port port)
> +{
> +	u32 tmp;
> +	u32 divider;
> +	u32 dsi_rate;
> +	u32 pll_ratio;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +
> +	/* Clear old configurations */
> +	tmp = I915_READ(BXT_MIPI_CLOCK_CTL);
> +	tmp &= ~(BXT_MIPI_TX_ESCLK_FIXDIV_MASK(port));
> +	tmp &= ~(BXT_MIPI_RX_ESCLK_FIXDIV_MASK(port));
> +	tmp &= ~(BXT_MIPI_ESCLK_VAR_DIV_MASK(port));
> +	tmp &= ~(BXT_MIPI_DPHY_DIVIDER_MASK(port));
> +
> +	/* Get the current DSI rate(actual) */
> +	pll_ratio = I915_READ(BXT_DSI_PLL_CTL) &
> +				BXT_DSI_PLL_RATIO_MASK;

Please do not use registers as temp storage. Pass the information into
this function instead.

> +	dsi_rate = (BXT_REF_CLOCK_KHZ * pll_ratio) / 2;
> +
> +	/* Max possible output of clock is 39.5 MHz, program value -1 */
> +	divider = (dsi_rate / BXT_MAX_VAR_OUTPUT_KHZ) - 1;
> +	tmp |= BXT_MIPI_ESCLK_VAR_DIV(port, divider);
> +
> +	/* Tx escape clock should be >=20MHz, so select divide by 2 */

Here the comment is useful as it contains rationale...

> +	tmp |= BXT_MIPI_TX_ESCLK_8XDIV_BY2(port);
> +
> +	/* Rx escape clock, select fix divide by 3 clock */

...however this just describes what should be obvious from the code.

> +	tmp |= BXT_MIPI_RX_ESCLK_8X_BY3(port);
> +
> +	/* Do the honors */

Useless comment.

> +	I915_WRITE(BXT_MIPI_CLOCK_CTL, tmp);
> +}
> +
>  static bool bxt_configure_dsi_pll(struct intel_encoder *encoder)
>  {
>  	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
> @@ -435,6 +470,8 @@ static bool bxt_configure_dsi_pll(struct intel_encoder *encoder)
>  static void bxt_enable_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);
> +	enum port port;
>  	u32 val;
>  
>  	DRM_DEBUG_KMS("\n");
> @@ -453,6 +490,10 @@ static void bxt_enable_dsi_pll(struct intel_encoder *encoder)
>  		return;
>  	}
>  
> +	/* Now program TX, RX, Dphy clocks */
> +	for_each_dsi_port(port, intel_dsi->ports)
> +		bxt_dsi_program_clocks(encoder->base.dev, port);
> +
>  	/* Enable DSI PLL */
>  	val = I915_READ(BXT_DSI_PLL_ENABLE);
>  	val |= BXT_DSI_PLL_DO_ENABLE;
> -- 
> 1.7.9.5
>

-- 
Jani Nikula, Intel Open Source Technology Center
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