linux-kernel - Re: [PATCH v9 0/8] Add endpoint driver for R-Car PCIe controller

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Date:   Thu, 7 May 2020 18:53:46 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Tom Joseph <tjoseph@...ence.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Marek Vasut <marek.vasut+renesas@...il.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        LAK <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v9 0/8] Add endpoint driver for R-Car PCIe controller

Hi Pavel,

On Thu, May 7, 2020 at 6:44 PM Pavel Machek <pavel@....cz> wrote:
>
> Hi!
>
>
> > R-Car/RZ-G2x SoC's, this also extends the epf framework to handle multiple windows
> > supported by the controller for mapping PCI address locally.
> >
> > Note:
> > The cadence/rockchip/designware endpoint drivers are build tested only.
> >
> > Changes for v9 (Re-spun this series as there were minimal changes requested):
> ...
> > * Replaced mdelay(1) with usleep_range(1000, 1001) in rcar_pcie_ep_assert_intx()
>
> Are you sure that is good idea? You are requesting 1ms sleep time with 1us tolerance,
> I dont believe common systems can do that.
>
Agreed the systems cannot do that, but the main reason of replacing
mdelay(1) with usleep_range(1000, 1001) was since  pci_epc_raise_irq()
calls mutex_lock() and then this function rcar_pcie_ep_assert_intx(),
so we can assume this function also can sleep. And, according to
Documentation/timers/timers-howto.rst, we should use usleep_range()
instead of mdelay().

Cheers,
--Prabhakar



> Best regards,
>                                                                         Pavel
>
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html