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From: Bjorn Helgaas <helgaas@kernel.org>
To: Vidya Sagar <vidyas@nvidia.com>
Cc: jingoohan1@gmail.com, gustavo.pimentel@synopsys.com,
	lorenzo.pieralisi@arm.com, bhelgaas@google.com,
	amurray@thegoodpenguin.co.uk, robh@kernel.org,
	treding@nvidia.com, jonathanh@nvidia.com,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	kthota@nvidia.com, mmaddireddy@nvidia.com, sagar.tv@gmail.com
Subject: Re: [PATCH V3 2/2] PCI: dwc: Add support to configure for ECRC
Date: Mon, 2 Nov 2020 17:02:34 -0600	[thread overview]
Message-ID: <20201102230234.GA62945@bjorn-Precision-5520> (raw)
In-Reply-To: <20201029053959.31361-3-vidyas@nvidia.com>

On Thu, Oct 29, 2020 at 11:09:59AM +0530, Vidya Sagar wrote:
> DesignWare core has a TLP digest (TD) override bit in one of the control
> registers of ATU. This bit also needs to be programmed for proper ECRC
> functionality. This is currently identified as an issue with DesignWare
> IP version 4.90a. This patch does the required programming in ATU upon
> querying the system policy for ECRC.

I guess this is a hardware defect, right?

How much of a problem would it be if we instead added a "no_ecrc"
quirk for this hardware so we never enabled ECRC?

IIUC, the current Linux support of ECRC is a single choice at
boot-time: by default ECRC is not enabled, but if you boot with
"pci=ecrc=on", we turn on ECRC for every device.

That seems like the minimal support, but I think the spec allows ECRC
to be enabled selectively, on individual devices.  I can imagine a
sysfs knob that would allow us to enable/disable ECRC per-device at
run-time.

If we had such a sysfs knob, it would be pretty ugly and maybe
impractical to work around this hardware issue.  So I'm a little bit
hesitant to add functionality that might have to be removed in the
future.

> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
> Reviewed-by: Jingoo Han <jingoohan1@gmail.com>
> ---
> V3:
> * Added 'Reviewed-by: Jingoo Han <jingoohan1@gmail.com>'
> 
> V2:
> * Addressed Jingoo's review comment
> * Removed saving 'td' bit information in 'dw_pcie' structure
> 
>  drivers/pci/controller/dwc/pcie-designware.c | 8 ++++++--
>  drivers/pci/controller/dwc/pcie-designware.h | 1 +
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index b5e438b70cd5..cbd651b219d2 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -246,6 +246,8 @@ static void dw_pcie_prog_outbound_atu_unroll(struct dw_pcie *pci, u8 func_no,
>  	dw_pcie_writel_ob_unroll(pci, index, PCIE_ATU_UNR_UPPER_TARGET,
>  				 upper_32_bits(pci_addr));
>  	val = type | PCIE_ATU_FUNC_NUM(func_no);
> +	if (pci->version == 0x490A)
> +		val = val | pcie_is_ecrc_enabled() << PCIE_ATU_TD_SHIFT;
>  	val = upper_32_bits(size - 1) ?
>  		val | PCIE_ATU_INCREASE_REGION_SIZE : val;
>  	dw_pcie_writel_ob_unroll(pci, index, PCIE_ATU_UNR_REGION_CTRL1, val);
> @@ -294,8 +296,10 @@ static void __dw_pcie_prog_outbound_atu(struct dw_pcie *pci, u8 func_no,
>  			   lower_32_bits(pci_addr));
>  	dw_pcie_writel_dbi(pci, PCIE_ATU_UPPER_TARGET,
>  			   upper_32_bits(pci_addr));
> -	dw_pcie_writel_dbi(pci, PCIE_ATU_CR1, type |
> -			   PCIE_ATU_FUNC_NUM(func_no));
> +	val = type | PCIE_ATU_FUNC_NUM(func_no);
> +	if (pci->version == 0x490A)
> +		val = val | pcie_is_ecrc_enabled() << PCIE_ATU_TD_SHIFT;
> +	dw_pcie_writel_dbi(pci, PCIE_ATU_CR1, val);
>  	dw_pcie_writel_dbi(pci, PCIE_ATU_CR2, PCIE_ATU_ENABLE);
>  
>  	/*
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index e7f441441db2..b01ef407fd52 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -89,6 +89,7 @@
>  #define PCIE_ATU_TYPE_IO		0x2
>  #define PCIE_ATU_TYPE_CFG0		0x4
>  #define PCIE_ATU_TYPE_CFG1		0x5
> +#define PCIE_ATU_TD_SHIFT		8
>  #define PCIE_ATU_FUNC_NUM(pf)           ((pf) << 20)
>  #define PCIE_ATU_CR2			0x908
>  #define PCIE_ATU_ENABLE			BIT(31)
> -- 
> 2.17.1
> 

  parent reply	other threads:[~2020-11-02 23:02 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-29  5:39 [PATCH V3 0/2] Add support to configure DWC " Vidya Sagar
2020-10-29  5:39 ` [PATCH V3 1/2] PCI/AER: Add pcie_is_ecrc_enabled() API Vidya Sagar
2020-10-29  5:39 ` [PATCH V3 2/2] PCI: dwc: Add support to configure for ECRC Vidya Sagar
2020-10-29 22:03   ` Jingoo Han
2020-10-30  6:45     ` Vidya Sagar
2020-11-02 14:15   ` Rob Herring
2020-11-02 14:27     ` Vidya Sagar
2020-11-02 15:11       ` Gustavo Pimentel
2020-11-02 21:16         ` Rob Herring
2020-11-02 22:38           ` Gustavo Pimentel
2020-11-03 19:48             ` Rob Herring
2020-11-02 23:02   ` Bjorn Helgaas [this message]
2020-11-03  3:27     ` Vidya Sagar
2020-11-03 21:07       ` Bjorn Helgaas
2020-11-04 11:43         ` Vidya Sagar
2020-11-04 16:22           ` Bjorn Helgaas
2020-11-04 17:40             ` Vidya Sagar

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