linux-kernel - Re: [PATCH v2] PCI: dwc: fix scheduling while atomic issues

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Date:   Wed, 22 Aug 2018 10:45:46 +0100
From:   Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>
To:     Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        "Lorenzo Pieralisi" <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] PCI: dwc: fix scheduling while atomic issues

Hi Jisheng

On 21/08/2018 07:15, Jisheng Zhang wrote:
> When programming inbound/outbound atu, we call usleep_range() after
> each checking PCIE_ATU_ENABLE bit. Unfortunately, the atu programming
> can be called in atomic context:
> 
> inbound atu programming could be called through
> pci_epc_write_header()
>   =>dw_pcie_ep_write_header()
>     =>dw_pcie_prog_inbound_atu()
> 
> outbound atu programming could be called through
> pci_bus_read_config_dword()
>   =>dw_pcie_rd_conf()
>     =>dw_pcie_prog_outbound_atu()
> 
> Fix this issue by calling mdelay() instead.

Makes sense. Thanks.

Acked-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>

Regards,
Gustavo

> 
> Signed-off-by: Jisheng Zhang <Jisheng.Zhang@...aptics.com>
> ---
> 
> Since v1
>  - use mdelay() instead of udelay() to avoid __bad_udelay()
> 
>  drivers/pci/controller/dwc/pcie-designware.c | 8 ++++----
>  drivers/pci/controller/dwc/pcie-designware.h | 3 +--
>  2 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 778c4f76a884..2153956a0b20 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -135,7 +135,7 @@ static void dw_pcie_prog_outbound_atu_unroll(struct dw_pcie *pci, int index,
>  		if (val & PCIE_ATU_ENABLE)
>  			return;
>  
> -		usleep_range(LINK_WAIT_IATU_MIN, LINK_WAIT_IATU_MAX);
> +		mdelay(LINK_WAIT_IATU);
>  	}
>  	dev_err(pci->dev, "Outbound iATU is not being enabled\n");
>  }
> @@ -178,7 +178,7 @@ void dw_pcie_prog_outbound_atu(struct dw_pcie *pci, int index, int type,
>  		if (val & PCIE_ATU_ENABLE)
>  			return;
>  
> -		usleep_range(LINK_WAIT_IATU_MIN, LINK_WAIT_IATU_MAX);
> +		mdelay(LINK_WAIT_IATU);
>  	}
>  	dev_err(pci->dev, "Outbound iATU is not being enabled\n");
>  }
> @@ -236,7 +236,7 @@ static int dw_pcie_prog_inbound_atu_unroll(struct dw_pcie *pci, int index,
>  		if (val & PCIE_ATU_ENABLE)
>  			return 0;
>  
> -		usleep_range(LINK_WAIT_IATU_MIN, LINK_WAIT_IATU_MAX);
> +		mdelay(LINK_WAIT_IATU);
>  	}
>  	dev_err(pci->dev, "Inbound iATU is not being enabled\n");
>  
> @@ -282,7 +282,7 @@ int dw_pcie_prog_inbound_atu(struct dw_pcie *pci, int index, int bar,
>  		if (val & PCIE_ATU_ENABLE)
>  			return 0;
>  
> -		usleep_range(LINK_WAIT_IATU_MIN, LINK_WAIT_IATU_MAX);
> +		mdelay(LINK_WAIT_IATU);
>  	}
>  	dev_err(pci->dev, "Inbound iATU is not being enabled\n");
>  
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 96126fd8403c..9f1a5e399b70 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -26,8 +26,7 @@
>  
>  /* Parameters for the waiting for iATU enabled routine */
>  #define LINK_WAIT_MAX_IATU_RETRIES	5
> -#define LINK_WAIT_IATU_MIN		9000
> -#define LINK_WAIT_IATU_MAX		10000
> +#define LINK_WAIT_IATU			9
>  
>  /* Synopsys-specific PCIe configuration registers */
>  #define PCIE_PORT_LINK_CONTROL		0x710
>