[PATCH 6/6] i.MX6: pci: Avoid aborts when asserting PCIe reset

[Lucas Stach]

Am Donnerstag, den 31.12.2015, 21:58 -0800 schrieb Andrey Smirnov:
> When booting Barebox in the HW environment where PCIe core has been
> used but not properly shut down, writing to PCIE_PL_PFLR in
> imx6_pcie_assert_core_reset would cause data abort exception.
> 
> The problem can be easily reproduced on a i.MX6 based board with PCIe
> slot populated with some device by doing:
> 
> > bootm -f -e 0x1050 <your board's>.img
> 
> Ignoring this exception seem to allow PCIe core to successfully
> initialize and enumerate devices properly. This is also how Linux
> Kernel version of the driver handles this situation -- it installs
> dummy no-op abort handler at the beginning of device's probing.
> 
> Signed-off-by: Andrey Smirnov <andrew.smirnov at gmail.com>

This isn't a complete fix, as it will only work if the clock tree is
unchanged. The proper solution is to shut the pcie core down before
jumping into the next image. I'll post a patch for this shortly.

But as it is increasing the odds that reinitializing an improperly
shutdown core succeeds, it is useful by itself, so:

Reviewed-by: Lucas Stach <l.stach at pengutronix.de>

> ---
>  drivers/pci/pci-imx6.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pci/pci-imx6.c b/drivers/pci/pci-imx6.c
> index 713007b..3a3edd8 100644
> --- a/drivers/pci/pci-imx6.c
> +++ b/drivers/pci/pci-imx6.c
> @@ -13,6 +13,7 @@
> 
>  #include <common.h>
>  #include <clock.h>
> +#include <abort.h>
>  #include <malloc.h>
>  #include <io.h>
>  #include <init.h>
> @@ -237,7 +238,10 @@ static int imx6_pcie_assert_core_reset(struct pcie_port *pp)
>  		val = readl(pp->dbi_base + PCIE_PL_PFLR);
>  		val &= ~PCIE_PL_PFLR_LINK_STATE_MASK;
>  		val |= PCIE_PL_PFLR_FORCE_LINK;
> +
> +		data_abort_mask();
>  		writel(val, pp->dbi_base + PCIE_PL_PFLR);
> +		data_abort_unmask();
> 
>  		gpr12 &= ~IMX6Q_GPR12_PCIE_CTL_2;
>  		writel(gpr12, imx6_pcie->iomuxc_gpr + IOMUXC_GPR12);
> --
> 2.5.0
> 
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