linux-kernel - RE: [RFC PATCH v2 1/3] PCI: hisi: re-architect Hip05/Hip06 controllers driver to preapare for ACPI

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Date:	Mon, 8 Feb 2016 16:06:54 +0000
From:	Gabriele Paoloni <gabriele.paoloni@...wei.com>
To:	Arnd Bergmann <arnd@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
CC:	"Guohanjun (Hanjun Guo)" <guohanjun@...wei.com>,
	"Wangzhou (B)" <wangzhou1@...ilicon.com>,
	"liudongdong (C)" <liudongdong3@...wei.com>,
	Linuxarm <linuxarm@...wei.com>, qiujiang <qiujiang@...wei.com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"Lorenzo.Pieralisi@....com" <Lorenzo.Pieralisi@....com>,
	"tn@...ihalf.com" <tn@...ihalf.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xuwei (O)" <xuwei5@...ilicon.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"jcm@...hat.com" <jcm@...hat.com>,
	zhangjukuo <zhangjukuo@...wei.com>,
	"Liguozhu (Kenneth)" <liguozhu@...ilicon.com>
Subject: RE: [RFC PATCH v2 1/3] PCI: hisi: re-architect Hip05/Hip06
 controllers driver to preapare for ACPI

Hi Arnd

> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@...db.de]
> Sent: 08 February 2016 13:50
> To: linux-arm-kernel@...ts.infradead.org
> Cc: Gabriele Paoloni; Guohanjun (Hanjun Guo); Wangzhou (B); liudongdong
> (C); Linuxarm; qiujiang; bhelgaas@...gle.com;
> Lorenzo.Pieralisi@....com; tn@...ihalf.com; linux-pci@...r.kernel.org;
> linux-kernel@...r.kernel.org; xuwei (O); linux-acpi@...r.kernel.org;
> jcm@...hat.com; zhangjukuo; Liguozhu (Kenneth)
> Subject: Re: [RFC PATCH v2 1/3] PCI: hisi: re-architect Hip05/Hip06
> controllers driver to preapare for ACPI
> 
> On Monday 08 February 2016 12:41:02 Gabriele Paoloni wrote:
> > +
> > +/* HipXX PCIe host only supports 32-bit config access */
> > +int hisi_pcie_common_cfg_read(void __iomem *reg_base, int where, int
> size,
> > +			      u32 *val)
> > +{
> > +	u32 reg;
> > +	u32 reg_val;
> > +	void *walker = &reg_val;
> > +
> > +	walker += (where & 0x3);
> > +	reg = where & ~0x3;
> > +	reg_val = readl(reg_base + reg);
> > +
> > +	if (size == 1)
> > +		*val = *(u8 __force *) walker;
> > +	else if (size == 2)
> > +		*val = *(u16 __force *) walker;
> > +	else if (size == 4)
> > +		*val = reg_val;
> > +	else
> > +		return PCIBIOS_BAD_REGISTER_NUMBER;
> > +
> > +	return PCIBIOS_SUCCESSFUL;
> > +}
> 
> Isn't this the same hack that Qualcomm are using?

As far as I can see Qualcomm defines its own config access
mechanism only for RC config read and also it seems they're
having problems with reporting the device class...

https://github.com/torvalds/linux/blob/master/drivers/pci/host/pcie-qcom.c#L474

Our problem is that our HW can only perform 32b rd/wr accesses
So we can't use readw/readb/writew/writeb...

Thanks

Gab

> 
> 	Arnd