linux-kernel - Re: [PATCH] phy: ufs-qcom: Invert PCS ready logic for SDM845 UFS

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Date:   Tue, 10 Dec 2019 11:02:11 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Evan Green <evgreen@...omium.org>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Can Guo <cang@...eaurora.org>,
        Douglas Anderson <dianders@...omium.org>,
        linux-kernel@...r.kernel.org, Andy Gross <agross@...nel.org>,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] phy: ufs-qcom: Invert PCS ready logic for SDM845 UFS

On Mon 09 Dec 14:00 PST 2019, Evan Green wrote:

> The SDM845 UFS phy seems to want to do a low transition to become
> ready, rather than a high transition. Without this, I am unable to
> enumerate UFS on SDM845 when booted from USB.
> 
> Fixes: 14ced7e3a1a ('phy: qcom-qmp: Correct ready status, again')
> 
> Signed-off-by: Evan Green <evgreen@...omium.org>

As concluded offline, the current logic is correct, but for some reason
we need a longer timeout on this particular device.

Regards,
Bjorn

> ---
> 
> Bjorn,
> At this point I'm super confused on what the correct behavior
> should be. Lack of documentation doesn't help. I'm worried that this
> change breaks UFS on some other platforms, so I'm hoping you or some
> PHY folks might have some advice on what the right thing to do is.
> 
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c b/drivers/phy/qualcomm/phy-qcom-qmp.c
> index 091e20303a14d..c4f4294360b6e 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
> @@ -1657,7 +1657,7 @@ static int qcom_qmp_phy_enable(struct phy *phy)
>  	if (cfg->type == PHY_TYPE_UFS) {
>  		status = pcs + cfg->regs[QPHY_PCS_READY_STATUS];
>  		mask = PCS_READY;
> -		ready = PCS_READY;
> +		ready = 0;
>  	} else {
>  		status = pcs + cfg->regs[QPHY_PCS_STATUS];
>  		mask = PHYSTATUS;
> -- 
> 2.21.0
>