linux-kernel - Re: [PATCHv5 18/20] PCI: mobiveil: Disable IB and OB windows set by bootloader

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Message-ID: <20190617093040.GC18020@e121166-lin.cambridge.arm.com>
Date:   Mon, 17 Jun 2019 10:30:40 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     "Z.q. Hou" <zhiqiang.hou@....com>
Cc:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "l.subrahmanya@...iveil.co.in" <l.subrahmanya@...iveil.co.in>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Leo Li <leoyang.li@....com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        Mingkai Hu <mingkai.hu@....com>,
        "M.h. Lian" <minghuan.lian@....com>,
        Xiaowei Bao <xiaowei.bao@....com>
Subject: Re: [PATCHv5 18/20] PCI: mobiveil: Disable IB and OB windows set by
 bootloader

On Sat, Jun 15, 2019 at 05:03:33AM +0000, Z.q. Hou wrote:
> Hi Lorenzo,
> 
> > -----Original Message-----
> > From: Lorenzo Pieralisi [mailto:lorenzo.pieralisi@....com]
> > Sent: 2019年6月13日 0:24
> > To: Z.q. Hou <zhiqiang.hou@....com>; bhelgaas@...gle.com
> > Cc: linux-pci@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> > devicetree@...r.kernel.org; linux-kernel@...r.kernel.org;
> > robh+dt@...nel.org; mark.rutland@....com; l.subrahmanya@...iveil.co.in;
> > shawnguo@...nel.org; Leo Li <leoyang.li@....com>;
> > catalin.marinas@....com; will.deacon@....com; Mingkai Hu
> > <mingkai.hu@....com>; M.h. Lian <minghuan.lian@....com>; Xiaowei Bao
> > <xiaowei.bao@....com>
> > Subject: Re: [PATCHv5 18/20] PCI: mobiveil: Disable IB and OB windows set
> > by bootloader
> > 
> > On Fri, Apr 12, 2019 at 08:37:00AM +0000, Z.q. Hou wrote:
> > > From: Hou Zhiqiang <Zhiqiang.Hou@....com>
> > >
> > > Disable all inbound and outbound windows before set up the windows in
> > > kernel, in case transactions match the window set by bootloader.
> > 
> > There must be no PCI transactions ongoing at bootloader<->OS handover.
> >
> 
> Yes, exact.
>  
> > The bootloader needs fixing and this patch should be dropped, the host bridge
> > driver assumes the host bridge state is disabled,
> 
> The host bridge driver should not assumes the host state is disabled,
> actually u-boot enable/initialize the host and without disabling it
> when transfer the control to Linux.

Fix the bootloader and drop this patch, I explain to you why.

> > it will program the bridge
> > apertures from scratch with no ongoing transactions, anything deviating from
> > this behaviour is a bootloader bug and a recipe for disaster.
> 
> The point of this patch is not to fix the ongoing transaction issue,
> it is to avoid a potential issue which is caused by the outbound
> window enabled by bootloader overlapping with Linux enabled.

See above.

Lorenzo

> Thanks,
> Zhiqiang
>  
> > Lorenzo
> > 
> > > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@....com>
> > > Reviewed-by: Minghuan Lian <Minghuan.Lian@....com>
> > > Reviewed-by: Subrahmanya Lingappa <l.subrahmanya@...iveil.co.in>
> > > ---
> > > V5:
> > >  - No functionality change.
> > >
> > >  drivers/pci/controller/pcie-mobiveil.c | 25 +++++++++++++++++++++++++
> > >  1 file changed, 25 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/pcie-mobiveil.c
> > > b/drivers/pci/controller/pcie-mobiveil.c
> > > index 8dc87c7a600e..411e9779da12 100644
> > > --- a/drivers/pci/controller/pcie-mobiveil.c
> > > +++ b/drivers/pci/controller/pcie-mobiveil.c
> > > @@ -565,6 +565,24 @@ static int mobiveil_bringup_link(struct
> > mobiveil_pcie *pcie)
> > >  	return -ETIMEDOUT;
> > >  }
> > >
> > > +static void mobiveil_pcie_disable_ib_win(struct mobiveil_pcie *pcie,
> > > +int idx) {
> > > +	u32 val;
> > > +
> > > +	val = csr_readl(pcie, PAB_PEX_AMAP_CTRL(idx));
> > > +	val &= ~(1 << AMAP_CTRL_EN_SHIFT);
> > > +	csr_writel(pcie, val, PAB_PEX_AMAP_CTRL(idx)); }
> > > +
> > > +static void mobiveil_pcie_disable_ob_win(struct mobiveil_pcie *pcie,
> > > +int idx) {
> > > +	u32 val;
> > > +
> > > +	val = csr_readl(pcie, PAB_AXI_AMAP_CTRL(idx));
> > > +	val &= ~(1 << WIN_ENABLE_SHIFT);
> > > +	csr_writel(pcie, val, PAB_AXI_AMAP_CTRL(idx)); }
> > > +
> > >  static void mobiveil_pcie_enable_msi(struct mobiveil_pcie *pcie)  {
> > >  	phys_addr_t msg_addr = pcie->pcie_reg_base; @@ -585,6 +603,13 @@
> > > static int mobiveil_host_init(struct mobiveil_pcie *pcie)  {
> > >  	u32 value, pab_ctrl, type;
> > >  	struct resource_entry *win;
> > > +	int i;
> > > +
> > > +	/* Disable all inbound/outbound windows */
> > > +	for (i = 0; i < pcie->apio_wins; i++)
> > > +		mobiveil_pcie_disable_ob_win(pcie, i);
> > > +	for (i = 0; i < pcie->ppio_wins; i++)
> > > +		mobiveil_pcie_disable_ib_win(pcie, i);
> > >
> > >  	/* setup bus numbers */
> > >  	value = csr_readl(pcie, PCI_PRIMARY_BUS);
> > > --
> > > 2.17.1
> > >