linux-kernel - Re: [PATCH] PCI: cadence: respond to received PTM Requests

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Date:   Mon, 31 Jan 2022 16:05:18 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Christian Gmeiner <christian.gmeiner@...il.com>
Cc:     linux-kernel@...r.kernel.org, Tom Joseph <tjoseph@...ence.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
Subject: Re: [PATCH] PCI: cadence: respond to received PTM Requests

Update subject line to match previous conventions ("git log --oneline
drivers/pci/controller/cadence/pcie-cadence-host.c" to see).

On Mon, Jan 31, 2022 at 01:08:27PM +0100, Christian Gmeiner wrote:
> This enables the Controller [RP] to automatically respond
> with Response/ResponseD messages.

Update to imperative mood, e.g., "Enable Controller to ...":

  https://chris.beams.io/posts/git-commit/
  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/maintainer-tip.rst?id=v5.16#n134

> Signed-off-by: Christian Gmeiner <christian.gmeiner@...il.com>
> ---
>  drivers/pci/controller/cadence/pcie-cadence-host.c | 10 ++++++++++
>  drivers/pci/controller/cadence/pcie-cadence.h      |  4 ++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
> index fb96d37a135c..940c7dd701d6 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
> @@ -123,6 +123,14 @@ static int cdns_pcie_retrain(struct cdns_pcie *pcie)
>  	return ret;
>  }
>  
> +static void cdns_pcie_host_enable_ptm_response(struct cdns_pcie *pcie)
> +{
> +	u32 val;
> +
> +	val = cdns_pcie_readl(pcie, CDNS_PCIE_LM_PTM_CTRL);
> +	cdns_pcie_writel(pcie, CDNS_PCIE_LM_PTM_CTRL, val | CDNS_PCIE_LM_TPM_CTRL_PTMRSEN);

I assume this is some device-specific enable bit that is effectively
ANDed with PCI_PTM_CTRL_ENABLE in the Precision Time Measurement
Capability?

> +}
> +
>  static int cdns_pcie_host_start_link(struct cdns_pcie_rc *rc)
>  {
>  	struct cdns_pcie *pcie = &rc->pcie;
> @@ -501,6 +509,8 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
>  	if (rc->quirk_detect_quiet_flag)
>  		cdns_pcie_detect_quiet_min_delay_set(&rc->pcie);
>  
> +	cdns_pcie_host_enable_ptm_response(pcie);
> +
>  	ret = cdns_pcie_start_link(pcie);
>  	if (ret) {
>  		dev_err(dev, "Failed to start link\n");
> diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
> index c8a27b6290ce..9510ea513b8a 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence.h
> +++ b/drivers/pci/controller/cadence/pcie-cadence.h
> @@ -116,6 +116,10 @@
>  #define LM_RC_BAR_CFG_APERTURE(bar, aperture)		\
>  					(((aperture) - 2) << ((bar) * 8))
>  
> +/* PTM Control Register */
> +#define CDNS_PCIE_LM_PTM_CTRL 	(CDNS_PCIE_LM_BASE + 0x0DA8)
> +#define CDNS_PCIE_LM_TPM_CTRL_PTMRSEN 	BIT(17)
> +
>  /*
>   * Endpoint Function Registers (PCI configuration space for endpoint functions)
>   */
> -- 
> 2.34.1
>