linux-kernel - Re: [PATCH v2 2/3] phy: cdns-dphy: Add band config for dphy tx

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Message-ID: <YrLPz8OTaMImArC4@pendragon.ideasonboard.com>
Date:   Wed, 22 Jun 2022 11:16:15 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Rahul T R <r-ravikumar@...com>
Cc:     linux-phy@...ts.infradead.org, kishon@...com, vkoul@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        p.yadav@...com, tomi.valkeinen@...asonboard.com,
        linux-kernel@...r.kernel.org, jpawar@...ence.com,
        sjakhade@...ence.com, mparab@...ence.com,
        devicetree@...r.kernel.org, vigneshr@...com, lee.jones@...aro.org
Subject: Re: [PATCH v2 2/3] phy: cdns-dphy: Add band config for dphy tx

Hi Rahul,

Thank you for the patch.

On Wed, Jun 22, 2022 at 01:23:39PM +0530, Rahul T R wrote:
> Add support for band ctrl config for dphy tx.
> 
> Signed-off-by: Rahul T R <r-ravikumar@...com>
> ---
>  drivers/phy/cadence/cdns-dphy.c | 52 ++++++++++++++++++++++++++++++++-
>  1 file changed, 51 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/phy/cadence/cdns-dphy.c b/drivers/phy/cadence/cdns-dphy.c
> index ba042e39cfaf..ddfa524d8ce7 100644
> --- a/drivers/phy/cadence/cdns-dphy.c
> +++ b/drivers/phy/cadence/cdns-dphy.c
> @@ -4,6 +4,7 @@
>   */
>  
>  #include <linux/bitops.h>
> +#include <linux/bitfield.h>

Nitpicking, bitfield goes before bitops :-)

>  #include <linux/clk.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
> @@ -45,6 +46,10 @@
>  #define DPHY_CMN_OPDIV_FROM_REG		BIT(6)
>  #define DPHY_CMN_OPDIV(x)		((x) << 7)
>  
> +#define DPHY_BAND_CFG			DPHY_PCS(0x0)
> +#define DPHY_BAND_CFG_LEFT_BAND		GENMASK(4, 0)
> +#define DPHY_BAND_CFG_RIGHT_BAND	GENMASK(9, 5)
> +
>  #define DPHY_PSM_CFG			DPHY_PCS(0x4)
>  #define DPHY_PSM_CFG_FROM_REG		BIT(0)
>  #define DPHY_PSM_CLK_DIV(x)		((x) << 1)
> @@ -92,6 +97,22 @@ struct cdns_dphy {
>  	struct phy *phy;
>  };
>  
> +struct cdns_dphy_band {
> +	unsigned int min_rate;
> +	unsigned int max_rate;
> +};
> +
> +/* Order of bands is important since the index is the band number. */
> +static struct cdns_dphy_band tx_bands[] = {

static const

> +	{80, 100}, {100, 120}, {120, 160}, {160, 200}, {200, 240},
> +	{240, 320}, {320, 390}, {390, 450}, {450, 510}, {510, 560},
> +	{560, 640}, {640, 690}, {690, 770}, {770, 870}, {870, 950},
> +	{950, 1000}, {1000, 1200}, {1200, 1400}, {1400, 1600}, {1600, 1800},
> +	{1800, 2000}, {2000, 2200}, {2200, 2500}

The max_rate value of band N is always equal to the min_rate value of
band N+1. Could we store one only ?

> +};
> +
> +static int num_tx_bands = ARRAY_SIZE(tx_bands);

You can use ARRAY_SIZE(tx_bands) directly below and drop this.

> +
>  static int cdns_dsi_get_dphy_pll_cfg(struct cdns_dphy *dphy,
>  				     struct cdns_dphy_cfg *cfg,
>  				     struct phy_configure_opts_mipi_dphy *opts,
> @@ -232,6 +253,26 @@ static int cdns_dphy_config_from_opts(struct phy *phy,
>  	return 0;
>  }
>  
> +static int cdns_dphy_tx_get_band_ctrl(unsigned long hs_clk_rate)
> +{
> +	unsigned int rate;
> +	int i;
> +
> +	rate = hs_clk_rate / 1000000UL;
> +
> +	if (rate < tx_bands[0].min_rate || rate >= tx_bands[num_tx_bands - 1].max_rate)
> +		return -EOPNOTSUPP;
> +
> +	for (i = 0; i < num_tx_bands; i++) {
> +		if (rate >= tx_bands[i].min_rate && rate < tx_bands[i].max_rate)
> +			return i;
> +	}
> +
> +	/* Unreachable. */
> +	WARN(1, "Reached unreachable code.");

I'd drop the WARN() if it's really unreachable.

> +	return -EINVAL;
> +}
> +
>  static int cdns_dphy_validate(struct phy *phy, enum phy_mode mode, int submode,
>  			      union phy_configure_opts *opts)
>  {
> @@ -247,7 +288,8 @@ static int cdns_dphy_configure(struct phy *phy, union phy_configure_opts *opts)
>  {
>  	struct cdns_dphy *dphy = phy_get_drvdata(phy);
>  	struct cdns_dphy_cfg cfg = { 0 };
> -	int ret;
> +	int ret, band_ctrl;
> +	unsigned int reg;
>  
>  	ret = cdns_dphy_config_from_opts(phy, &opts->mipi_dphy, &cfg);
>  	if (ret)
> @@ -276,6 +318,14 @@ static int cdns_dphy_configure(struct phy *phy, union phy_configure_opts *opts)
>  	 */
>  	cdns_dphy_set_pll_cfg(dphy, &cfg);
>  
> +	band_ctrl = cdns_dphy_tx_get_band_ctrl(opts->mipi_dphy.hs_clk_rate);
> +	if (band_ctrl < 0)
> +		return band_ctrl;
> +
> +	reg = FIELD_PREP(DPHY_BAND_CFG_LEFT_BAND, band_ctrl) |
> +	      FIELD_PREP(DPHY_BAND_CFG_RIGHT_BAND, band_ctrl);
> +	writel(reg, dphy->regs + DPHY_BAND_CFG);
> +
>  	return 0;
>  }
>  

-- 
Regards,

Laurent Pinchart