linux-kernel - Re: [RESEND PATCH v3 4/7] PCI: dwc: all: Modify dbi accessors to take dbi

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Date:   Fri, 10 Mar 2017 17:06:44 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Niklas Cassel <niklas.cassel@...s.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-omap@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <nsekhar@...com>, Jingoo Han <jingoohan1@...il.com>,
        Richard Zhu <hongxing.zhu@....com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Murali Karicheri <m-karicheri2@...com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Jesper Nilsson <jespern@...s.com>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>
Subject: Re: [RESEND PATCH v3 4/7] PCI: dwc: all: Modify dbi accessors to take
 dbi_base as argument

Hi,

On Thursday 09 March 2017 08:35 PM, Niklas Cassel wrote:
> 
> 
> On 03/09/2017 03:48 PM, Niklas Cassel wrote:
>> On 03/09/2017 07:39 AM, Kishon Vijay Abraham I wrote:
>>> dwc has 2 dbi address space labeled dbics and dbics2. The existing
>>> helper to access dbi address space can access only dbics. However
>>> dbics2 has to be accessed for programming the BAR registers in the
>>> case of EP mode. This is in preparation for adding EP mode support
>>> to dwc driver.
>> Hello Kishon
>>
>> I don't really like the idea of adding an extra argument to every existing read/write.
>> Will not a read/write using dbi2 be quite uncommon compared to a read/write
>> using dbi?
>>
>> How about something like this:
>>
>> void __dw_pcie_writel(struct dw_pcie *pci, void __iomem *base, u32 reg, u32 val)
>> {
>>     if (pci->ops->writel_dbi)
>>         pci->ops->writel_dbi(pci, base, reg, val);
>>     else
>>         writel(val, base + reg);
>> }
>>
>> #define dw_pcie_writel_dbi(pci, reg, val) __dw_pcie_writel(pci, pci->dbi_base, reg, val)
>> #define dw_pcie_writel_dbi2(pci, reg, val) __dw_pcie_writel(pci, pci->dbi_base2, reg, val)
> 
> Perhaps make dw_pcie_writel_dbi2 a function rather than a define,
> so we can return an error if pci->dbi_base2 == NULL.

Should we return an error? We don't return error for dbi_base either. I think
it should be sufficient to return errors while populating dbi_base or
dbi_base2. Otherwise it's a bug and should result in abort. Joao?

Thanks
Kishon