On Wed, 2022-06-08 at 16:45 +0800, CK Hu wrote:

Hi, Rex:

On Mon, 2022-05-23 at 12:47 +0200, Guillaume Ranquet wrote:

quoted

From: Markus Schneider-Pargmann <msp@baylibre.com>

This patch adds a DisplayPort driver for the Mediatek mt8195 SoC.

It supports the mt8195, the embedded DisplayPort units. It offers
DisplayPort 1.4 with up to 4 lanes.

The driver creates a child device for the phy. The child device
will
never exist without the parent being active. As they are sharing a
register range, the parent passes a regmap pointer to the child so
that
both can work with the same register range. The phy driver sets
device
data that is read by the parent to get the phy device that can be
used
to control the phy properties.

This driver is based on an initial version by
Jason-JH.Lin [off-list ref].

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Signed-off-by: Guillaume Ranquet <redacted>
---

[snip]

quoted

+
+static bool mtk_dp_set_swing_pre_emphasis(struct mtk_dp *mtk_dp,
int
lane_num,
+					  int swing_val, int
preemphasis)

The return value is never processed, so let this function to be void.

Regards,
CK

Hello CK,

ok, I will drop this.
Actually, I change "mtk_dp_write", "mtk_dp_update_bits" and
"mtk_dp_bulk_16bit_write" to return void. I don't think we need to
handle the issue that we failed to set registers. If we failed to set
register, it's because hw is not enable.

Therefore, I drop this and we can reduce many lines of codes.

BRs,
Bo-Chen

quoted

+{
+	int ret;
+
+	u32 lane_shift = lane_num * DP_TX1_VOLT_SWING_SHIFT;
+
+	if (lane_num < 0 || lane_num > 3)

lane_num < 0 would not happen. lane_num > 3 only if device tree max
lane is wrong. So I would like to checkout max lane when parsing
device
tree instead of checking here.

quoted

+		return false;
+
+	dev_dbg(mtk_dp->dev,
+		"link training swing_val= 0x%x, preemphasis = 0x%x\n",
+		swing_val, preemphasis);
+
+	ret = mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_SWING_EMP,
+				 swing_val << (DP_TX0_VOLT_SWING_SHIFT
+ lane_shift),
+				 DP_TX0_VOLT_SWING_MASK << lane_shift);
+	if (ret)
+		return ret;
+	ret = mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_SWING_EMP,
+				 preemphasis << (DP_TX0_PRE_EMPH_SHIFT
+ lane_shift),
+				 DP_TX0_PRE_EMPH_MASK << lane_shift);
+
+	return !ret;
+}
+