linux-kernel - Re: [PATCH 1/2] PCI: dwc: dra7xx: Create functional dependency between PCIe and PHY

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Date:   Tue, 10 Oct 2017 10:19:28 +0300
From:   Roger Quadros <rogerq@...com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     <linux-omap@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <nsekhar@...com>
Subject: Re: [PATCH 1/2] PCI: dwc: dra7xx: Create functional dependency
 between PCIe and PHY


Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

On 09/10/17 12:03, Kishon Vijay Abraham I wrote:
> PCI core access configuration space registers in resume_noirq callbacks.
> In the case of dra7xx, PIPE3 PHY connected to PCIe controller has to be
> enabled before accessing configuration space registers. Since
> PIPE3 PHY is enabled by only configuring control module registers, no
> aborts has been observed so far (though during noirq stage, interface
> clock of PIPE3 PHY is not enabled).
> 
> With new TRM updates, PIPE3 PHY has to be initialized (PIPE3 PHY
> registers has to be accessed) as well which requires the interface
> clock of PIPE3 PHY to be enabled. The interface clock of PIPE3 PHY is
> derived from OCP2SCP and hence PCIe PHY is modeled as a child of
> OCP2SCP. Since pm_runtime is not enabled during noirq stage,
> pm_runtime_get_sync done in phy_init doesn't enable
> OCP2SCP clocks resulting in abort when PIPE3 PHY registers are
> accessed.

This could be the case not only with PCIe but even with USB and SATA?
Maybe today it doesn't complain because USB/SATA is being resumed (by chance) after PHY?

> 
> Create a function dependency between PCIe and PHY here to make
> sure PCIe is suspended before PCIe PHY/OCP2SCP and resumed after
> PCIe PHY/OCP2SCP.
> 
> Suggested-by: Grygorii Strashko <grygorii.strashko@...com>
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> Signed-off-by: Sekhar Nori <nsekhar@...com>
> ---
>  drivers/pci/dwc/pci-dra7xx.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/pci/dwc/pci-dra7xx.c b/drivers/pci/dwc/pci-dra7xx.c
> index 34427a6a15af..362607f727ee 100644
> --- a/drivers/pci/dwc/pci-dra7xx.c
> +++ b/drivers/pci/dwc/pci-dra7xx.c
> @@ -11,6 +11,7 @@
>   */
>  
>  #include <linux/delay.h>
> +#include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
> @@ -594,6 +595,7 @@ static int __init dra7xx_pcie_probe(struct platform_device *pdev)
>  	int i;
>  	int phy_count;
>  	struct phy **phy;
> +	struct device_link **link;
>  	void __iomem *base;
>  	struct resource *res;
>  	struct dw_pcie *pci;
> @@ -649,11 +651,21 @@ static int __init dra7xx_pcie_probe(struct platform_device *pdev)
>  	if (!phy)
>  		return -ENOMEM;
>  
> +	link = devm_kzalloc(dev, sizeof(*link) * phy_count, GFP_KERNEL);
> +	if (!link)
> +		return -ENOMEM;
> +
>  	for (i = 0; i < phy_count; i++) {
>  		snprintf(name, sizeof(name), "pcie-phy%d", i);
>  		phy[i] = devm_phy_get(dev, name);
>  		if (IS_ERR(phy[i]))
>  			return PTR_ERR(phy[i]);
> +
> +		link[i] = device_link_add(dev, &phy[i]->dev, DL_FLAG_STATELESS);
> +		if (!link[i]) {
> +			ret = -EINVAL;
> +			goto err_link;
> +		}
>  	}
>  
>  	dra7xx->base = base;
> @@ -732,6 +744,10 @@ static int __init dra7xx_pcie_probe(struct platform_device *pdev)
>  	pm_runtime_disable(dev);
>  	dra7xx_pcie_disable_phy(dra7xx);
>  
> +err_link:
> +	while (--i >= 0)
> +		device_link_del(link[i]);
> +
>  	return ret;
>  }
>  
> 

-- 
cheers,
-roger