linux-kernel - RE: [PATCH 2/2] pci/layerscape: change the default error response behavior

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Message-ID: <AM5PR0402MB27711353F4479D83E41359D8844B0@AM5PR0402MB2771.eurprd04.prod.outlook.com>
Date:   Thu, 12 Oct 2017 03:33:15 +0000
From:   "Z.q. Hou" <zhiqiang.hou@....com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "Roy Zang" <roy.zang@....com>, Mingkai Hu <mingkai.hu@....com>,
        "M.h. Lian" <minghuan.lian@....com>
Subject: RE: [PATCH 2/2] pci/layerscape: change the default error response
 behavior

Hi Bjorn,

Thanks a lot for your review!

> -----Original Message-----
> From: Bjorn Helgaas [mailto:helgaas@...nel.org]
> Sent: 2017年10月12日 3:41
> To: Z.q. Hou <zhiqiang.hou@....com>
> Cc: linux-kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> linux-pci@...r.kernel.org; bhelgaas@...gle.com; Roy Zang
> <roy.zang@....com>; Mingkai Hu <mingkai.hu@....com>; M.h. Lian
> <minghuan.lian@....com>
> Subject: Re: [PATCH 2/2] pci/layerscape: change the default error response
> behavior
> 
> On Fri, Sep 22, 2017 at 03:25:22PM +0800, Zhiqiang Hou wrote:
> > From: Minghuan Lian <Minghuan.Lian@....com>
> >
> > By default, when the PCIe controller experiences an erroneous
> > completion from an external completer for its outbound non-posted
> > request, it always sends an OKAY response to the device's internal AXI
> > slave system interface. However, such default system error response
> > behavior cannot be used for other types of outbound non-posted
> > requests. For example, the outbound memory read transaction requires
> > an actual ERROR response, like UR completion or completion timeout.
> > The patch is to fix it by forwarding the error response of the
> > non-posted request.
> >
> > Signed-off-by: Minghuan Lian <Minghuan.Lian@....com>
> > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@....com>
> > ---
> >  drivers/pci/dwc/pci-layerscape.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/drivers/pci/dwc/pci-layerscape.c
> > b/drivers/pci/dwc/pci-layerscape.c
> > index 3b01e309a55e..a647090c140e 100644
> > --- a/drivers/pci/dwc/pci-layerscape.c
> > +++ b/drivers/pci/dwc/pci-layerscape.c
> > @@ -33,6 +33,8 @@
> >
> >  /* PEX Internal Configuration Registers */
> >  #define PCIE_STRFMR1		0x71c /* Symbol Timer & Filter Mask
> Register1 */
> > +#define PCIE_ABSERR		0x8d0 /* Bridge Slave Error Response
> Register */
> > +#define PCIE_ABSERR_SETTING	0x9401 /* Forward error of non-posted
> request */
> >
> >  #define PCIE_IATU_NUM		6
> >
> > @@ -54,6 +56,19 @@ struct ls_pcie {
> >
> >  #define to_ls_pcie(x)	dev_get_drvdata((x)->dev)
> >
> > +static int err_response_flag = 1;
> > +
> > +static int __init ls_pcie_param(char *p) {
> > +	if (p && strncmp(p, "no-err-response", 15) == 0)
> > +		err_response_flag = 0;
> > +	else
> > +		err_response_flag = 1;
> > +
> > +	return 0;
> > +}
> > +early_param("ls_pcie", ls_pcie_param);
> 
> What's the point of this parameter?  If it's for debugging, it's not clear that
> we need it upstream.  If it's for debugging and we *do* need it upstream,
> there should be some sort of comment to that effect.
> 
> I assume you never expect an end user to need this parameter.

It is for debugging, will drop this parameter next version.

> 
> >  static bool ls_pcie_is_bridge(struct ls_pcie *pcie)  {
> >  	struct dw_pcie *pci = pcie->pci;
> > @@ -124,6 +139,14 @@ static int ls_pcie_link_up(struct dw_pcie *pci)
> >  	return 1;
> >  }
> >
> > +/* Forward error response of outbound non-posted requests */ static
> > +void ls_pcie_fix_error_response(struct ls_pcie *pcie) {
> > +	struct dw_pcie *pci = pcie->pci;
> > +
> > +	iowrite32(PCIE_ABSERR_SETTING, pci->dbi_base + PCIE_ABSERR); }
> > +
> >  static int ls_pcie_host_init(struct pcie_port *pp)  {
> >  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp); @@ -135,6 +158,8 @@
> > static int ls_pcie_host_init(struct pcie_port *pp)
> >  	 * dw_pcie_setup_rc() will reconfigure the outbound windows.
> >  	 */
> >  	ls_pcie_disable_outbound_atus(pcie);
> > +	if (err_response_flag)
> > +		ls_pcie_fix_error_response(pcie);
> >
> >  	dw_pcie_dbi_ro_wr_en(pci);
> >  	ls_pcie_clear_multifunction(pcie);
> > --
> > 2.14.1
> >

Thanks,
Zhiqiang