[PATCH] arm64: a37xx: pci: Disable link training when unloading driver

[Pali Rohár]

On Wednesday 23 September 2020 08:45:20 Stefan Roese wrote:
> On 22.09.20 13:21, Pali Rohár wrote:
> > As required by PCI Express spec a delay for at least 100ms after
> > de-asserting PERST# signal is needed before link training is enabled.
> > 
> > Linux kernels prior to 5.8 version do not automatically disable link
> > training before de-asserting PERST# signal, therefore this requirement is
> > not fulfilled.
> > 
> > Above requirement is needed for proper detection of some Compex PCIe WiFi
> > cards. Otherwise Linux kernel cannot detect it.
> > 
> > To allow using those PCIe cards with older Linux kernel versions booted by
> > U-Boot compiled with U-Boot a37xx pci driver, disable link training in
> > U-Boot when unloading this pci driver.
> > 
> > Thanks to DM_FLAG_OS_PREPARE flag, U-Boot automatically unload this driver
> > when booting Linux kernel.
> > 
> > Signed-off-by: Pali Rohár <pali at kernel.org>
> 
> Reviewed-by: Stefan Roese <sr at denx.de>
> 
> Thanks,
> Stefan

Ok! Stefan, will you send this patch to main u-boot, so it would be part
of the u-boot 2020.10 release?

> > ---
> >   drivers/pci/pci-aardvark.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/pci/pci-aardvark.c b/drivers/pci/pci-aardvark.c
> > index b2c417701f..babb84ca93 100644
> > --- a/drivers/pci/pci-aardvark.c
> > +++ b/drivers/pci/pci-aardvark.c
> > @@ -647,10 +647,15 @@ static int pcie_advk_probe(struct udevice *dev)
> >   static int pcie_advk_remove(struct udevice *dev)
> >   {
> >   	struct pcie_advk *pcie = dev_get_priv(dev);
> > +	u32 reg;
> >   	if (dm_gpio_is_valid(&pcie->reset_gpio))
> >   		dm_gpio_set_value(&pcie->reset_gpio, 1);
> > +	reg = advk_readl(pcie, PCIE_CORE_CTRL0_REG);
> > +	reg &= ~LINK_TRAINING_EN;
> > +	advk_writel(pcie, reg, PCIE_CORE_CTRL0_REG);
> > +
> >   	return 0;
> >   }
> > 
> 
> 
> Viele Grüße,
> Stefan
> 
> -- 
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-51 Fax: (+49)-8142-66989-80 Email: sr at denx.de