On Fri, Oct 16, 2020 at 2:04 PM <marek.vasut@xxxxxxxxx> wrote:
> From: Marek Vasut <marek.vasut+renesas@xxxxxxxxx>
>
> The R-Car PCIe controller is capable of handling L0s/L1 link states.
> While the controller can enter and exit L0s link state, and exit L1
> link state, without any additional action from the driver, to enter
> L1 link state, the driver must complete the link state transition by
> issuing additional commands to the controller.
>
> The problem is, this transition is not atomic. The controller sets
> PMEL1RX bit in PMSR register upon reception of PM_ENTER_L1 DLLP from
> the PCIe card, but then the controller enters some sort of inbetween
> state. The driver must detect this condition and complete the link
> state transition, by setting L1IATN bit in PMCTLR and waiting for
> the link state transition to complete.
>
> If a PCIe access happens inside this window, where the controller
> is between L0 and L1 link states, the access generates a fault and
> the ARM 'imprecise external abort' handler is invoked.
>
> Just like other PCI controller drivers, here we hook the fault handler,
> perform the fixup to help the controller enter L1 link state, and then
> restart the instruction which triggered the fault. Since the controller
> is in L1 link state now, the link can exit from L1 link state to L0 and
> successfully complete the access.
>
> Note that this fixup is applicable only to Aarch32 R-Car controllers,
> the Aarch64 R-Car perform the same fixup in TFA, see TFA commit [1]
> 0969397f2 ("rcar_gen3: plat: Prevent PCIe hang during L1X config access")
> [1] https://github.com/ARM-software/arm-trusted-firmware/commit/0969397f295621aa26b3d14b76dd397d22be58bf
>
> Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
> Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> Cc: linux-renesas-soc@xxxxxxxxxxxxxxx
> ---
> V2: - Update commit message, add link to TFA repository commit
> - Handle the LPAE case as in ARM fault.c and fsr-{2,3}level.c
> - Cache clock and check whether they are enabled before register
> access
> V3: - Fix commit message according to spellchecker
> - Use of_find_matching_node() to apply hook only on Gen1 and Gen2 RCar
> (in case the kernel is multiplatform)
> V4: - Mark rcar_pcie_abort_handler_of_match with __initconst
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Please add tags given to the previous version:
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
