linux-kernel - Re: [PATCH 4/5] phy: qcom: edp: Introduce support for DisplayPort

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Message-ID: <ZRqIHSetajQf7Um1@hovoldconsulting.com>
Date:   Mon, 2 Oct 2023 11:06:37 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
Cc:     Vinod Koul <vkoul@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: Re: [PATCH 4/5] phy: qcom: edp: Introduce support for DisplayPort

On Tue, Aug 09, 2022 at 09:07:44PM -0700, Bjorn Andersson wrote:
> The eDP phy can be used to drive either eDP or DP output, with some
> minor variations in some of the configuration and seemingly a need for
> implementing swing and pre_emphasis calibration.
> 
> Introduce a config object, indicating if the phy is operating in eDP or
> DP mode and swing/pre-emphasis calibration to support this.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
>  drivers/phy/qualcomm/phy-qcom-edp.c | 80 +++++++++++++++++++++++++++--
>  1 file changed, 76 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-edp.c b/drivers/phy/qualcomm/phy-qcom-edp.c
> index 32614fb838b5..301ac422d2fe 100644
> --- a/drivers/phy/qualcomm/phy-qcom-edp.c
> +++ b/drivers/phy/qualcomm/phy-qcom-edp.c
> @@ -70,8 +70,19 @@
>  
>  #define TXn_TRAN_DRVR_EMP_EN                    0x0078
>  
> +struct qcom_edp_cfg {
> +	bool is_dp;
> +
> +	/* DP PHY swing and pre_emphasis tables */
> +	const u8 (*swing_hbr_rbr)[4][4];
> +	const u8 (*swing_hbr3_hbr2)[4][4];
> +	const u8 (*pre_emphasis_hbr_rbr)[4][4];
> +	const u8 (*pre_emphasis_hbr3_hbr2)[4][4];
> +};
 
>  static int qcom_edp_configure_ssc(const struct qcom_edp *edp)
> @@ -315,7 +381,9 @@ static int qcom_edp_set_vco_div(const struct qcom_edp *edp)
>  static int qcom_edp_phy_power_on(struct phy *phy)
>  {
>  	const struct qcom_edp *edp = phy_get_drvdata(phy);
> +	const struct qcom_edp_cfg *cfg = edp->cfg;
>  	u32 bias0_en, drvr0_en, bias1_en, drvr1_en;
> +	u8 ldo_config;
>  	int timeout;
>  	int ret;
>  	u32 val;
> @@ -332,8 +400,11 @@ static int qcom_edp_phy_power_on(struct phy *phy)
>  	if (timeout)
>  		return timeout;
>  
> -	writel(0x01, edp->tx0 + TXn_LDO_CONFIG);
> -	writel(0x01, edp->tx1 + TXn_LDO_CONFIG);
> +
> +	ldo_config = (cfg && cfg->is_dp) ? 0x1 : 0x0;
> +
> +	writel(ldo_config, edp->tx0 + TXn_LDO_CONFIG);
> +	writel(ldo_config, edp->tx1 + TXn_LDO_CONFIG);

When reviewing a patch from Konrad which will start using the eDP
configuration on the X13s, I noticed that this patch inverted these bits
for older SoCs (e.g. sc7280 and sc8180xp). They used to be set to 1,
but after this patch they will be set to 0.

Was that intentional even if it was never mentioned in the commit
message? Or was it a mistake that should be fixed?

Johan