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 13:31:27 +0100
From:   Niklas Cassel <niklas.cassel@...s.com>
To:     Kishon Vijay Abraham I <kishon@...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

On 03/10/2017 12:36 PM, Kishon Vijay Abraham I wrote:
> 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?

Sorry for previous empty email.


What I meant to write:

Right now we do error checking for dbi_base in platform specific code
and in pcie-designware-host.c:dw_pcie_host_init.

For dbi_base2, you've added error checking in platform specific code
(pci-dra7xx.c), but I don't see any error checking in your patch proposal
pcie-designware-ep.c:dw_pcie_ep_init.
If you add error checking in dw_pcie_ep_init, then I agree,
we don't need any error checking in dw_pcie_writel_dbi2.



>
> Thanks
> Kishon