[PATCH 4/4] drm/mediatek: config mipitx impedance with calibration data

[CK Hu]

Hi, Jitao:

On Mon, 2019-12-16 at 16:29 +0800, Jitao Shi wrote:
> Read calibration data from nvmem, and config mipitx impedance with
> calibration data to make sure their impedance are 100ohm.
> 
> Signed-off-by: Jitao Shi <jitao.shi at mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_mipi_tx.h        |  1 +
>  drivers/gpu/drm/mediatek/mtk_mt8183_mipi_tx.c | 63 +++++++++++++++++++
>  2 files changed, 64 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_mipi_tx.h b/drivers/gpu/drm/mediatek/mtk_mipi_tx.h
> index eea44327fe9f..a1b6292145de 100644
> --- a/drivers/gpu/drm/mediatek/mtk_mipi_tx.h
> +++ b/drivers/gpu/drm/mediatek/mtk_mipi_tx.h
> @@ -28,6 +28,7 @@ struct mtk_mipi_tx {
>  	void __iomem *regs;
>  	u32 data_rate;
>  	u32 mipitx_drive;
> +	u32 rt_code[5];
>  	const struct mtk_mipitx_data *driver_data;
>  	struct clk_hw pll_hw;
>  	struct clk *pll;
> diff --git a/drivers/gpu/drm/mediatek/mtk_mt8183_mipi_tx.c b/drivers/gpu/drm/mediatek/mtk_mt8183_mipi_tx.c
> index 124fdf95f1e5..f624516944bb 100644
> --- a/drivers/gpu/drm/mediatek/mtk_mt8183_mipi_tx.c
> +++ b/drivers/gpu/drm/mediatek/mtk_mt8183_mipi_tx.c
> @@ -5,6 +5,8 @@
>   */
>  
>  #include "mtk_mipi_tx.h"
> +#include <linux/nvmem-consumer.h>
> +#include <linux/slab.h>
>  
>  #define MIPITX_LANE_CON		0x000c
>  #define RG_DSI_CPHY_T1DRV_EN		BIT(0)
> @@ -28,6 +30,7 @@
>  #define MIPITX_PLL_CON4		0x003c
>  #define RG_DSI_PLL_IBIAS		(3 << 10)
>  
> +#define MIPITX_D2P_RTCODE	0x0100
>  #define MIPITX_D2_SW_CTL_EN	0x0144
>  #define MIPITX_D0_SW_CTL_EN	0x0244
>  #define MIPITX_CK_CKMODE_EN	0x0328
> @@ -108,6 +111,64 @@ static const struct clk_ops mtk_mipi_tx_pll_ops = {
>  	.recalc_rate = mtk_mipi_tx_pll_recalc_rate,
>  };
>  
> +static int mtk_mipi_tx_config_calibration_data(struct mtk_mipi_tx *mipi_tx)
> +{
> +	u32 *buf = NULL;

Need not to assign NULL to buf, it would be assigned some value later.

> +	int i, j;
> +	struct nvmem_cell *cell;
> +	struct device *dev = mipi_tx->dev;
> +	size_t len;
> +
> +	cell = nvmem_cell_get(dev, "calibration-data");
> +	if (IS_ERR(cell)) {
> +		dev_warn(dev, "nvmem_cell_get fail\n");

In [1], nvmem is optional property, so I think you should use dev_dbg()
or dev_info().

[1]
http://lists.infradead.org/pipermail/linux-mediatek/2019-December/025640.html

> +		return -EINVAL;

The caller does not process return value, so I think you don't need to
return value.

> +	}
> +
> +	buf = (u32 *)nvmem_cell_read(cell, &len);
> +
> +	nvmem_cell_put(cell);
> +
> +	if (IS_ERR(buf)) {
> +		dev_warn(dev, "can't get data\n");
> +		return -EINVAL;
> +	}
> +
> +	if (len < 3 * sizeof(u32)) {
> +		dev_warn(dev, "invalid calibration data\n");
> +		kfree(buf);
> +		return -EINVAL;
> +	}
> +
> +	mipi_tx->rt_code[0] = ((buf[0] >> 6 & 0x1F) << 5) |

You don't access rt_code[] out of this function, so I think this could
be local variable.

> +			      (buf[0] >> 11 & 0x1F);

Lower case 0x1f.

> +	mipi_tx->rt_code[1] = ((buf[1] >> 27 & 0x1F) << 5) |
> +			      (buf[0] >> 1 & 0x1F);
> +	mipi_tx->rt_code[2] = ((buf[1] >> 17 & 0x1F) << 5) |
> +			      (buf[1] >> 22 & 0x1F);
> +	mipi_tx->rt_code[3] = ((buf[1] >> 7 & 0x1F) << 5) |
> +			      (buf[1] >> 12 & 0x1F);
> +	mipi_tx->rt_code[4] = ((buf[2] >> 27 & 0x1F) << 5) |
> +			      (buf[1] >> 2 & 0x1F);

Why not just save rt_code in nvmem and you don't need to translate here?
If you need to do so, please add description for this.

> +
> +	for (i = 0; i < 5; i++) {
> +		if ((mipi_tx->rt_code[i] & 0x1F) == 0)
> +			mipi_tx->rt_code[i] |= 0x10;
> +
> +		if ((mipi_tx->rt_code[i] >> 5 & 0x1F) == 0)
> +			mipi_tx->rt_code[i] |= 0x10 << 5;
> +
> +		for (j = 0; j < 10; j++) {
> +			mtk_mipi_tx_update_bits(mipi_tx,
> +				MIPITX_D2P_RTCODE * (i + 1) + j * 4,
> +				1, mipi_tx->rt_code[i] >> j & 1);
> +		}

There is only one statement in for-loop, so you could get rid of {}.

Regards,
CK

> +	}
> +
> +	kfree(buf);
> +	return 0;
> +}
> +
>  static void mtk_mipi_tx_power_on_signal(struct phy *phy)
>  {
>  	struct mtk_mipi_tx *mipi_tx = phy_get_drvdata(phy);
> @@ -130,6 +191,8 @@ static void mtk_mipi_tx_power_on_signal(struct phy *phy)
>  				RG_DSI_HSTX_LDO_REF_SEL,
>  				mipi_tx->mipitx_drive << 6);
>  
> +	mtk_mipi_tx_config_calibration_data(mipi_tx);
> +
>  	mtk_mipi_tx_set_bits(mipi_tx, MIPITX_CK_CKMODE_EN, DSI_CK_CKMODE_EN);
>  }
>