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SubjectRE: [PATCHv5 18/20] PCI: mobiveil: Disable IB and OB windows set by bootloader
Date
Hi Lorenzo,

> -----Original Message-----
> From: Lorenzo Pieralisi [mailto:lorenzo.pieralisi@arm.com]
> Sent: 2019年6月13日 0:24
> To: Z.q. Hou <zhiqiang.hou@nxp.com>; bhelgaas@google.com
> Cc: linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org;
> robh+dt@kernel.org; mark.rutland@arm.com; l.subrahmanya@mobiveil.co.in;
> shawnguo@kernel.org; Leo Li <leoyang.li@nxp.com>;
> catalin.marinas@arm.com; will.deacon@arm.com; Mingkai Hu
> <mingkai.hu@nxp.com>; M.h. Lian <minghuan.lian@nxp.com>; Xiaowei Bao
> <xiaowei.bao@nxp.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@nxp.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.

> 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.

Thanks,
Zhiqiang

> Lorenzo
>
> > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> > Reviewed-by: Minghuan Lian <Minghuan.Lian@nxp.com>
> > Reviewed-by: Subrahmanya Lingappa <l.subrahmanya@mobiveil.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
> >
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