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From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Marek Vasut <marek.vasut@gmail.com>
Cc: linux-pci <linux-pci@vger.kernel.org>,
	Marek Vasut <marek.vasut+renesas@gmail.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Wolfram Sang <wsa@the-dreams.de>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH V4] PCI: rcar: Add L1 link state fix into data abort hook
Date: Sat, 17 Oct 2020 16:03:05 +0200	[thread overview]
Message-ID: <CAMuHMdUR1=+mX7RnrL2e4+kiR=pa9vPc3GVyUBOVsf+DFei2Aw@mail.gmail.com> (raw)
In-Reply-To: <20201016120416.7008-1-marek.vasut@gmail.com>

On Fri, Oct 16, 2020 at 2:04 PM <marek.vasut@gmail.com> wrote:
> From: Marek Vasut <marek.vasut+renesas@gmail.com>
>
> 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@gmail.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> Cc: linux-renesas-soc@vger.kernel.org
> ---
> 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@glider.be>

Please add tags given to the previous version:
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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

  reply	other threads:[~2020-10-17 14:03 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-16 12:04 [PATCH V4] PCI: rcar: Add L1 link state fix into data abort hook marek.vasut
2020-10-17 14:03 ` Geert Uytterhoeven [this message]
2020-11-19 17:35 ` Lorenzo Pieralisi
2020-11-29 13:05   ` Marek Vasut
2020-12-08 10:18     ` Lorenzo Pieralisi
2020-12-08 17:45       ` Marek Vasut
2020-12-08 17:52         ` Geert Uytterhoeven
2020-12-08 16:40 ` Bjorn Helgaas
2020-12-08 18:05   ` Marek Vasut
2020-12-08 18:46     ` Bjorn Helgaas
2020-12-10 12:12       ` Lorenzo Pieralisi
2020-12-12 19:12         ` Marek Vasut
2020-12-14 17:13           ` Lorenzo Pieralisi
2020-12-16 17:52             ` Marek Vasut
2020-12-12 19:10       ` Marek Vasut
2020-12-14 20:38     ` Bjorn Helgaas
2020-12-16 17:56       ` Marek Vasut
2020-12-16 18:20         ` Bjorn Helgaas

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