Re: [PATCH V3 07/12] PCI: tegra: Disable AFI dynamic clock gating

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Oct 30, 2017 at 07:27:18PM +0530, Manikanta Maddireddy wrote:
> When there are 32 outstanding writes from AFI to memory, the outstanding
> write counter overflows and indicates that there are "0" outstanding write
> transactions. This outstanding write counter is used to generate IDLE
> signal to dynamically gate the AFI clock.
> 
> When memory controller is under heavy load, its possible that write
> completions will come back to AFI after long delay and AFI write counter
> overflows. AFI clock gets gated even when there are outstanding
> transactions towards memory controller resutling in system hang.
> 
> Disable dynamic clock gating of AFI clock to avoid system hang.
> 
> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> ---
> V3:
> * no change in this patch
> V2:
> * no change in this patch
> 
>  drivers/pci/host/pci-tegra.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
> index 4562b0c113a8..c264037112cb 100644
> --- a/drivers/pci/host/pci-tegra.c
> +++ b/drivers/pci/host/pci-tegra.c
> @@ -103,8 +103,9 @@
>  #define AFI_MSI_EN_VEC6		0xa4
>  #define AFI_MSI_EN_VEC7		0xa8
>  
> -#define AFI_CONFIGURATION		0xac
> -#define  AFI_CONFIGURATION_EN_FPCI	(1 << 0)
> +#define AFI_CONFIGURATION			0xac
> +#define  AFI_CONFIGURATION_EN_FPCI		(1 << 0)
> +#define  AFI_CONFIGURATION_CLKEN_OVERRIDE	(1 << 31)
>  
>  #define AFI_FPCI_ERROR_MASKS	0xb0
>  
> @@ -1059,9 +1060,10 @@ static int tegra_pcie_enable_controller(struct tegra_pcie *pcie)
>  		}
>  	}
>  
> -	/* finally enable PCIe */
> +	/* Disable AFI dynamic clock gating and enable PCIe */
>  	value = afi_readl(pcie, AFI_CONFIGURATION);
> -	value |= AFI_CONFIGURATION_EN_FPCI;
> +	value |= (AFI_CONFIGURATION_EN_FPCI |
> +			AFI_CONFIGURATION_CLKEN_OVERRIDE);

I think this is cleaner (and results in a smaller diff) if you simply
put this on a new line:

	value |= AFI_CONFIGURATION_CLKEN_OVERRIDE;

Thierry

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