linux-kernel - Re: [PATCH] PCI: mediatek-gen3: Print LTSSM state when PCIe link down

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Date:   Mon, 28 Mar 2022 16:39:41 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Jianjun Wang <jianjun.wang@...iatek.com>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-pci@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        jieyy.yang@...iatek.com, chuanjia.liu@...iatek.com,
        qizhong.cheng@...iatek.com, jian.yang@...iatek.com
Subject: Re: [PATCH] PCI: mediatek-gen3: Print LTSSM state when PCIe link down

Il 24/03/22 08:25, Jianjun Wang ha scritto:
> Print current LTSSM state when PCIe link down instead of the register
> value, make it easier to get the link status.
> 
> Signed-off-by: Jianjun Wang <jianjun.wang@...iatek.com>

Hello Jianjun,
this patch is really helpful when comes to understand the source of an issue,
so I agree with it - and thank you for that.

Though, I think that you should still print the hex number along with the
meaning of it, check below:

> ---
>   drivers/pci/controller/pcie-mediatek-gen3.c | 40 ++++++++++++++++++++-
>   1 file changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> index 7705d61fba4c..54663f025e27 100644
> --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c

..snip..

> @@ -327,8 +358,15 @@ static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie)
>   				 !!(val & PCIE_PORT_LINKUP), 20,
>   				 PCI_PM_D3COLD_WAIT * USEC_PER_MSEC);
>   	if (err) {
> +		const char *ltssm_state;
> +		int ltssm_index;
> +
>   		val = readl_relaxed(pcie->base + PCIE_LTSSM_STATUS_REG);
> -		dev_err(pcie->dev, "PCIe link down, ltssm reg val: %#x\n", val);
> +		ltssm_index = PCIE_LTSSM_STATE(val);
> +		ltssm_state = ltssm_index >= ARRAY_SIZE(ltssm_str) ?
> +			      "Unknown state" : ltssm_str[ltssm_index];
> +		dev_err(pcie->dev, "PCIe link down, current ltssm state: %s\n",

There, I think that you should do:

dev_err(pcie->dev, "PCIe link down, current LTSSM state: %s (%#x)\n",
	ltssm_state, val);

this will be extremely useful in the "Unknown state" case.

After fixing that,

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

Regards,
Angelo