RE: [PATCHv5 18/20] PCI: mobiveil: Disable IB and OB windows set by bootloader

[Z.q. Hou]

Hi Lorenzo,

> -----Original Message-----
> From: Lorenzo Pieralisi [mailto:lorenzo.pieralisi@xxxxxxx]
> Sent: 2019年6月13日 0:24
> To: Z.q. Hou <zhiqiang.hou@xxxxxxx>; bhelgaas@xxxxxxxxxx
> Cc: linux-pci@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx; l.subrahmanya@xxxxxxxxxxxxxx;
> shawnguo@xxxxxxxxxx; Leo Li <leoyang.li@xxxxxxx>;
> catalin.marinas@xxxxxxx; will.deacon@xxxxxxx; Mingkai Hu
> <mingkai.hu@xxxxxxx>; M.h. Lian <minghuan.lian@xxxxxxx>; Xiaowei Bao
> <xiaowei.bao@xxxxxxx>
> 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@xxxxxxx>
> >
> > 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@xxxxxxx>
> > Reviewed-by: Minghuan Lian <Minghuan.Lian@xxxxxxx>
> > Reviewed-by: Subrahmanya Lingappa <l.subrahmanya@xxxxxxxxxxxxxx>
> > ---
> > 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
> >