linux-kernel - Re: [PATCH V12 01/12] PCI: Add #defines for some of PCIe spec r4.0 features

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Date:   Tue, 9 Jul 2019 09:14:27 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Vidya Sagar <vidyas@...dia.com>
Cc:     lorenzo.pieralisi@....com, robh+dt@...nel.org,
        mark.rutland@....com, thierry.reding@...il.com,
        jonathanh@...dia.com, kishon@...com, catalin.marinas@....com,
        will.deacon@....com, jingoohan1@...il.com,
        gustavo.pimentel@...opsys.com, digetx@...il.com,
        mperttunen@...dia.com, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kthota@...dia.com, mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V12 01/12] PCI: Add #defines for some of PCIe spec r4.0
 features

On Mon, Jul 01, 2019 at 06:09:59PM +0530, Vidya Sagar wrote:
> Add #defines only for the Data Link Feature and Physical Layer 16.0 GT/s
> features.
> 
> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> Reviewed-by: Thierry Reding <treding@...dia.com>

Please include spec references in the commit log, e.g., PCIe r5.0, sec
7.7.4, for Data Link Feature and sec 7.7.5 for Physical Layer 16 GT/s.

>  include/uapi/linux/pci_regs.h | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index f28e562d7ca8..1c79f6a097d2 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -713,7 +713,9 @@
>  #define PCI_EXT_CAP_ID_DPC	0x1D	/* Downstream Port Containment */
>  #define PCI_EXT_CAP_ID_L1SS	0x1E	/* L1 PM Substates */
>  #define PCI_EXT_CAP_ID_PTM	0x1F	/* Precision Time Measurement */
> -#define PCI_EXT_CAP_ID_MAX	PCI_EXT_CAP_ID_PTM
> +#define PCI_EXT_CAP_ID_DLF	0x25	/* Data Link Feature */
> +#define PCI_EXT_CAP_ID_PL	0x26	/* Physical Layer 16.0 GT/s */

Maybe PCI_EXT_CAP_ID_PL_16GT so there's a little more hint of what
this is for?

> +#define PCI_EXT_CAP_ID_MAX	PCI_EXT_CAP_ID_PL
>  
>  #define PCI_EXT_CAP_DSN_SIZEOF	12
>  #define PCI_EXT_CAP_MCAST_ENDPOINT_SIZEOF 40
> @@ -1053,4 +1055,22 @@
>  #define  PCI_L1SS_CTL1_LTR_L12_TH_SCALE	0xe0000000  /* LTR_L1.2_THRESHOLD_Scale */
>  #define PCI_L1SS_CTL2		0x0c	/* Control 2 Register */
>  
> +/* Data Link Feature */
> +#define PCI_DLF_CAP		0x04	/* Capabilities Register */
> +#define  PCI_DLF_LOCAL_DLF_SUP_MASK	0x007fffff  /* Local Data Link Feature Supported */
> +#define  PCI_DLF_EXCHANGE_ENABLE	0x80000000  /* Data Link Feature Exchange Enable */
> +#define PCI_DLF_STS		0x08	/* Status Register */
> +#define  PCI_DLF_REMOTE_DLF_SUP_MASK	0x007fffff  /* Remote Data Link Feature Supported */
> +#define  PCI_DLF_REMOTE_DLF_SUP_VALID	0x80000000  /* Remote Data Link Feature Support Valid */

I'm a little bit ambivalent about adding #defines that aren't used.  I
personally would probably just add the things we use, so the header
file gives a clue about what's currently implemented.  But I guess
either way is fine.

> +/* Physical Layer 16.0 GT/s */
> +#define PCI_PL_16GT_CAP		0x04	/* Capabilities Register */
> +#define PCI_PL_16GT_CTRL	0x08	/* Control Register */
> +#define PCI_PL_16GT_STS		0x0c	/* Status Register */
> +#define PCI_PL_16GT_LDPM_STS	0x10	/* Local Data Parity Mismatch Status Register */
> +#define PCI_PL_16GT_FRDPM_STS	0x14	/* First Retimer Data Parity Mismatch Status Register */
> +#define PCI_PL_16GT_SRDPM_STS	0x18	/* Second Retimer Data Parity Mismatch Status Register */
> +#define PCI_PL_16GT_RSVD	0x1C	/* Reserved */

Use lower-case hex consistently here.  There's no global consistency
in this file, but we can at least be consistent in each section.  But
I'm even more hesitant about included unused #defines for "reserved"
fields, so if you drop this it would take care of both :)

> +#define PCI_PL_16GT_LE_CTRL	0x20	/* Lane Equalization Control Register */

This is the only register you actually use.  You defined a local
PL16G_CAP_OFF_DSP_16G_TX_PRESET_MASK for this register.  Shouldn't
that be defined here instead of in
drivers/pci/controller/dwc/pcie-tegra194.c?

>  #endif /* LINUX_PCI_REGS_H */
> -- 
> 2.17.1
>