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

CK Hu
2019-12-20T02:36:16Z

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@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);
> }
>