linux-kernel - Re: [PATCH v6 2/2] PCI: cadence: Retrain Link to work around Gen2 training defect.

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Message-ID: <20201229223146.3081aa50@windsurf>
Date:   Tue, 29 Dec 2020 22:31:46 +0100
From:   Thomas Petazzoni <thomas.petazzoni@...tlin.com>
To:     Nadeem Athani <nadeem@...ence.com>
Cc:     <tjoseph@...ence.com>, <lorenzo.pieralisi@....com>,
        <robh@...nel.org>, <bhelgaas@...gle.com>, <kishon@...com>,
        <linux-omap@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, mparab@...ence.com,
        pthombar@...ence.com, sjakhade@...ence.com
Subject: Re: [PATCH v6 2/2] PCI: cadence: Retrain Link to work around Gen2
 training defect.

On Mon, 28 Dec 2020 15:05:10 +0100
Nadeem Athani <nadeem@...ence.com> wrote:

> +static void cdns_pcie_retrain(struct cdns_pcie *pcie)

Shouldn't this propagate a return value ?

> +{
> +	u32 lnk_cap_sls, pcie_cap_off = CDNS_PCIE_RP_CAP_OFFSET;
> +	u16 lnk_stat, lnk_ctl;
> +
> +	/*
> +	 * Set retrain bit if current speed is 2.5 GB/s,
> +	 * but the PCIe root port support is > 2.5 GB/s.
> +	 */
> +
> +	lnk_cap_sls = cdns_pcie_readl(pcie, (CDNS_PCIE_RP_BASE + pcie_cap_off +
> +					     PCI_EXP_LNKCAP));
> +	if ((lnk_cap_sls & PCI_EXP_LNKCAP_SLS) <= PCI_EXP_LNKCAP_SLS_2_5GB)
> +		return;
> +
> +	lnk_stat = cdns_pcie_rp_readw(pcie, pcie_cap_off + PCI_EXP_LNKSTA);
> +	if ((lnk_stat & PCI_EXP_LNKSTA_CLS) == PCI_EXP_LNKSTA_CLS_2_5GB) {
> +		lnk_ctl = cdns_pcie_rp_readw(pcie,
> +					     pcie_cap_off + PCI_EXP_LNKCTL);
> +		lnk_ctl |= PCI_EXP_LNKCTL_RL;
> +		cdns_pcie_rp_writew(pcie, pcie_cap_off + PCI_EXP_LNKCTL,
> +				    lnk_ctl);
> +
> +		if (cdns_pcie_host_wait_for_link(pcie))
> +			return;

Here, shouldn't you return the status of
cdns_pcie_host_wait_for_link(), to propagate whether the PCIe link
indeed came up after the retrain ?

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com