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>,
"Arnd Bergmann" <arnd@arndb.de>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Geert Uytterhoeven" <geert+renesas@glider.be>,
"Krzysztof Wilczyński" <kw@linux.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 v5 2/2] PCI: rcar: Use PCI_SET_ERROR_RESPONSE after read which triggered an exception
Date: Wed, 23 Feb 2022 14:20:25 +0100 [thread overview]
Message-ID: <CAMuHMdU7gxmuhOPjh_awCE0XbjatfPEKRUH3=qzvEsmwReDjsQ@mail.gmail.com> (raw)
In-Reply-To: <20220219034604.603656-2-marek.vasut@gmail.com>
On Sat, Feb 19, 2022 at 4:46 AM <marek.vasut@gmail.com> wrote:
> From: Marek Vasut <marek.vasut+renesas@gmail.com>
>
> In case the controller is transitioning to L1 in rcar_pcie_config_access(),
> any read/write access to PCIECDR triggers asynchronous external abort. This
> is because the transition to L1 link state must be manually finished by the
> driver. The PCIe IP can transition back from L1 state to L0 on its own.
>
> The current asynchronous external abort hook implementation restarts
> the instruction which finally triggered the fault, which can be a
> different instruction than the read/write instruction which started
> the faulting access. Usually the instruction which finally triggers
> the fault is one which has some data dependency on the result of the
> read/write. In case of read, the read value after fixup is undefined,
> while a read value of faulting read should be PCI_ERROR_RESPONSE.
>
> It is possible to enforce the fault using 'isb' instruction placed
> right after the read/write instruction which started the faulting
> access. Add custom register accessors which perform the read/write
> followed immediately by 'isb'.
>
> This way, the fault always happens on the 'isb' and in case of read,
> which is located one instruction before the 'isb', it is now possible
> to fix up the return value of the read in the asynchronous external
> abort hook and make that read return PCI_ERROR_RESPONSE.
>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
With this series applied, my koelsch (R-Car M2-W) with Intel 9301CT
Gigabit Ethernet adapter survived 1000 suspend/resume cycles.
Before, it would lock-up after a handful tries.
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
next prev parent reply other threads:[~2022-02-23 13:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-19 3:46 [PATCH v5 1/2] PCI: rcar: Finish transition to L1 state in rcar_pcie_config_access() marek.vasut
2022-02-19 3:46 ` [PATCH v5 2/2] PCI: rcar: Use PCI_SET_ERROR_RESPONSE after read which triggered an exception marek.vasut
2022-02-23 13:20 ` Geert Uytterhoeven [this message]
2022-02-23 13:15 ` [PATCH v5 1/2] PCI: rcar: Finish transition to L1 state in rcar_pcie_config_access() Geert Uytterhoeven
2022-03-01 17:07 ` Lorenzo Pieralisi
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