linux-kernel - Re: [PATCH 04/13] PCI: cadence: Add support to start link and verify link status

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Message-ID: <16ffe86d-9061-1a9a-d536-561e20ecbdd7@ti.com>
Date:   Thu, 19 Dec 2019 17:31:04 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Andrew Murray <andrew.murray@....com>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-omap@...r.kernel.org>
Subject: Re: [PATCH 04/13] PCI: cadence: Add support to start link and verify
 link status

Hi Andrew,

On 17/12/19 5:28 pm, Andrew Murray wrote:
> On Mon, Dec 09, 2019 at 02:51:38PM +0530, Kishon Vijay Abraham I wrote:
>> Add cdns_pcie_ops to start link and verify link status. The registers
>> to start link and to check link status is in Platform specific PCIe
>> wrapper. Add support for platform specific drivers to add callback
>> functions for the PCIe Cadence core to start link and verify link status.
>>
>> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
>> ---
>>  .../pci/controller/cadence/pcie-cadence-ep.c  |  8 ++++++
>>  .../controller/cadence/pcie-cadence-host.c    | 28 +++++++++++++++++++
>>  drivers/pci/controller/cadence/pcie-cadence.h | 23 +++++++++++++++
>>  3 files changed, 59 insertions(+)
>>
>> diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
>> index 560f22b4d165..088394b6be04 100644
>> --- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
>> +++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
>> @@ -355,8 +355,10 @@ static int cdns_pcie_ep_start(struct pci_epc *epc)
>>  {
>>  	struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
>>  	struct cdns_pcie *pcie = &ep->pcie;
>> +	struct device *dev = pcie->dev;
>>  	struct pci_epf *epf;
>>  	u32 cfg;
>> +	int ret;
>>  
>>  	/*
>>  	 * BIT(0) is hardwired to 1, hence function 0 is always enabled
>> @@ -367,6 +369,12 @@ static int cdns_pcie_ep_start(struct pci_epc *epc)
>>  		cfg |= BIT(epf->func_no);
>>  	cdns_pcie_writel(pcie, CDNS_PCIE_LM_EP_FUNC_CFG, cfg);
>>  
>> +	ret = cdns_pcie_start_link(pcie, true);
>> +	if (ret) {
>> +		dev_err(dev, "Failed to start link\n");
>> +		return ret;
>> +	}
>> +
>>  	return 0;
>>  }
>>  
>> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
>> index ccf55e143e1d..0929554f5a81 100644
>> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
>> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
>> @@ -3,6 +3,7 @@
>>  // Cadence PCIe host controller driver.
>>  // Author: Cyrille Pitchen <cyrille.pitchen@...e-electrons.com>
>>  
>> +#include <linux/delay.h>
>>  #include <linux/kernel.h>
>>  #include <linux/of_address.h>
>>  #include <linux/of_pci.h>
>> @@ -201,6 +202,23 @@ static int cdns_pcie_host_init(struct device *dev,
>>  	return err;
>>  }
>>  
>> +static int cdns_pcie_host_wait_for_link(struct cdns_pcie *pcie)
>> +{
>> +	struct device *dev = pcie->dev;
>> +	int retries;
>> +
>> +	/* Check if the link is up or not */
>> +	for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) {
>> +		if (cdns_pcie_is_link_up(pcie)) {
>> +			dev_info(dev, "Link up\n");
>> +			return 0;
>> +		}
>> +		usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
>> +	}
>> +
>> +	return -ETIMEDOUT;
>> +}
> 
> This patch looks fine, except this function (above) is identical to
> dw_pcie_wait_for_link, advk_pcie_wait_for_link and nwl_wait_for_link. Even
> the definitions of LINK_WAIT_USLEEP_xx are the same.
> 
> I don't see any justification to duplicating this again - can you consolidate
> these functions to something that all controller drivers can use?

This involves reading a register, so this in entirety cannot be in a
generic layer. We could add "ops" for checking the link status (in
pci_ops?), but I'm not sure if that's really required.

Thanks
Kishon