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

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Date:   Fri, 18 Feb 2022 16:26:48 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        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

Hi Bjorn,

On 01/02/22 3:35 am, Bjorn Helgaas wrote:
> 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?

That's correct. This bit enables Controller [RP] to respond to the received PTM
Requests.

Thanks,
Kishon
> 
>> +}
>> +
>>  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
>>