RE: [PATCH 1/2] PCI: dwc: Add support to disable GEN3 equalization

[Gustavo Pimentel]

Hi,

On Tue, Sep 10, 2019 at 13:25:1, Pankaj Dubey <pankaj.dubey@xxxxxxxxxxx> 
wrote:

> From: Anvesh Salveru <anvesh.s@xxxxxxxxxxx>
> 
> In some platforms, PCIe PHY may have issues which will prevent linkup
> to happen in GEN3 or high speed. In case equalization fails, link will
> fallback to GEN1.
> 
> Designware controller has support for disabling GEN3 equalization if
> required. This patch enables the designware driver to disable the PCIe
> GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.

s/Designware/DesignWare
s/designware/DesignWare

> 
> Platform drivers can disable equalization by setting the dwc_pci_quirk
> flag DWC_EQUALIZATION_DISABLE.
> 
> Signed-off-by: Anvesh Salveru <anvesh.s@xxxxxxxxxxx>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@xxxxxxxxxxx>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
>  drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 7d25102..bf82091 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
>  		break;
>  	}
>  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> +
> +	val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> +
> +	if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> +		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> +
> +	dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
>  }
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index ffed084..a1453c5 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -29,6 +29,9 @@
>  #define LINK_WAIT_MAX_IATU_RETRIES	5
>  #define LINK_WAIT_IATU			9
>  
> +/* Parameters for PCIe Quirks */
> +#define DWC_EQUALIZATION_DISABLE	0x1
> +
>  /* Synopsys-specific PCIe configuration registers */
>  #define PCIE_PORT_LINK_CONTROL		0x710
>  #define PORT_LINK_MODE_MASK		GENMASK(21, 16)
> @@ -60,6 +63,9 @@
>  #define PCIE_MSI_INTR0_MASK		0x82C
>  #define PCIE_MSI_INTR0_STATUS		0x830
>  
> +#define PCIE_PORT_GEN3_RELATED		0x890
> +#define PORT_LOGIC_GEN3_EQ_DISABLE	BIT(16)
> +
>  #define PCIE_ATU_VIEWPORT		0x900
>  #define PCIE_ATU_REGION_INBOUND		BIT(31)
>  #define PCIE_ATU_REGION_OUTBOUND	0
> @@ -244,6 +250,7 @@ struct dw_pcie {
>  	struct dw_pcie_ep	ep;
>  	const struct dw_pcie_ops *ops;
>  	unsigned int		version;
> +	unsigned int		dwc_pci_quirk;

I'd prefer called this variable just quirk, the prefix is redundant here.

>  };
>  
>  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
> -- 
> 2.7.4

I understand your idea and I'm fine with it, but I just wonder if there 
isn't any other typical way to do this kind of quirks... I'm not seeing a 
similar case to this although.
For me makes more sense to squash both patches (1 and 2), since we aim to 
add this quirk especially because it focuses is on this "GEN3_RELATED" 
register in a logical patch.

Regards,
Gustavo