linux-kernel - Re: [PATCH V7 05/15] PCI: dwc: Add ext config space capability search API

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Date:   Tue, 21 May 2019 22:44:04 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     Thierry Reding <thierry.reding@...il.com>
CC:     <lorenzo.pieralisi@....com>, <bhelgaas@...gle.com>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <jonathanh@...dia.com>, <kishon@...com>, <catalin.marinas@....com>,
        <will.deacon@....com>, <jingoohan1@...il.com>,
        <gustavo.pimentel@...opsys.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 V7 05/15] PCI: dwc: Add ext config space capability search
 API

On 5/21/2019 4:06 PM, Thierry Reding wrote:
> On Fri, May 17, 2019 at 06:08:36PM +0530, Vidya Sagar wrote:
>> Add extended configuration space capability search API using struct dw_pcie *
>> pointer
>>
>> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
>> Acked-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
>> ---
>> Changes since [v6]:
>> * None
>>
>> Changes since [v5]:
>> * None
>>
>> Changes since [v4]:
>> * None
>>
>> Changes since [v3]:
>> * None
>>
>> Changes since [v2]:
>> * None
>>
>> Changes since [v1]:
>> * This is a new patch in v2 series
>>
>>   drivers/pci/controller/dwc/pcie-designware.c | 41 ++++++++++++++++++++
>>   drivers/pci/controller/dwc/pcie-designware.h |  1 +
>>   2 files changed, 42 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
>> index 8f53ce63d17e..3b7d50888caa 100644
>> --- a/drivers/pci/controller/dwc/pcie-designware.c
>> +++ b/drivers/pci/controller/dwc/pcie-designware.c
>> @@ -54,6 +54,47 @@ u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap)
>>   }
>>   EXPORT_SYMBOL_GPL(dw_pcie_find_capability);
>>   
>> +static int dw_pcie_find_next_ext_capability(struct dw_pcie *pci, int start,
>> +					    int cap)
> 
> Perhaps make this more consistent with the existing regular
> configuration space capability search API? Something like this perhaps:
> 
> 	static u16 dw_pcie_find_next_ext_capability(struct dw_pcie *pci,
> 						    u16 start, u8 cap)
> 
> ? I guess your variant above is consistent with the existing generic
> capability search API, so another alternative might be to make the old
> dw_pcie_find_capability() API consistent with everything else. It's
> confusing if we keep having to jump between the two variants.
Ok. I'll change it to the format being followed in this file i.e. using u16 and u8

> 
> Thierry
> 
>> +{
>> +	u32 header;
>> +	int ttl;
>> +	int pos = PCI_CFG_SPACE_SIZE;
>> +
>> +	/* minimum 8 bytes per capability */
>> +	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
>> +
>> +	if (start)
>> +		pos = start;
>> +
>> +	header = dw_pcie_readl_dbi(pci, pos);
>> +	/*
>> +	 * If we have no capabilities, this is indicated by cap ID,
>> +	 * cap version and next pointer all being 0.
>> +	 */
>> +	if (header == 0)
>> +		return 0;
>> +
>> +	while (ttl-- > 0) {
>> +		if (PCI_EXT_CAP_ID(header) == cap && pos != start)
>> +			return pos;
>> +
>> +		pos = PCI_EXT_CAP_NEXT(header);
>> +		if (pos < PCI_CFG_SPACE_SIZE)
>> +			break;
>> +
>> +		header = dw_pcie_readl_dbi(pci, pos);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +int dw_pcie_find_ext_capability(struct dw_pcie *pci, int cap)
>> +{
>> +	return dw_pcie_find_next_ext_capability(pci, 0, cap);
>> +}
>> +EXPORT_SYMBOL_GPL(dw_pcie_find_ext_capability);
>> +
>>   int dw_pcie_read(void __iomem *addr, int size, u32 *val)
>>   {
>>   	if (!IS_ALIGNED((uintptr_t)addr, size)) {
>> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
>> index 6cb978132469..fff284098117 100644
>> --- a/drivers/pci/controller/dwc/pcie-designware.h
>> +++ b/drivers/pci/controller/dwc/pcie-designware.h
>> @@ -252,6 +252,7 @@ struct dw_pcie {
>>   		container_of((endpoint), struct dw_pcie, ep)
>>   
>>   u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap);
>> +int dw_pcie_find_ext_capability(struct dw_pcie *pci, int cap);
>>   
>>   int dw_pcie_read(void __iomem *addr, int size, u32 *val);
>>   int dw_pcie_write(void __iomem *addr, int size, u32 val);
>> -- 
>> 2.17.1
>>