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Subject: Re: [PATCH 1/2] PCI: rcar: Poll more often in rcar_pcie_wait_for_dl()
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Simon Horman <horms@verge.net.au>,
        linux-pci <linux-pci@vger.kernel.org>,
        Marek Vasut <marek.vasut+renesas@gmail.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Phil Edworthy <phil.edworthy@renesas.com>,
        Wolfram Sang <wsa@the-dreams.de>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>
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From: Marek Vasut <marek.vasut@gmail.com>
Message-ID: <618f1841-f8b9-7fdb-5887-01a080a231db@gmail.com>
Date: Mon, 19 Mar 2018 11:56:24 +0100
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On 03/19/2018 11:53 AM, Geert Uytterhoeven wrote:
> Hi Marek,
> 
> On Mon, Mar 19, 2018 at 10:53 AM, Marek Vasut <marek.vasut@gmail.com> wrote:
>> On 03/19/2018 09:38 AM, Simon Horman wrote:
>>> On Sun, Mar 18, 2018 at 11:52:52AM +0100, Marek Vasut wrote:
>>>> The data link active signal usually takes ~20 uSec to be asserted,
>>>> poll the bit more often to avoid useless delays in this function.
>>>>
>>>> Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
>>>> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
>>>> Cc: Phil Edworthy <phil.edworthy@renesas.com>
>>>> Cc: Simon Horman <horms+renesas@verge.net.au>
>>>> Cc: Wolfram Sang <wsa@the-dreams.de>
>>>> Cc: linux-renesas-soc@vger.kernel.org
>>>
>>> Unless my eyes deceive me this seems to be quite a lot (100x) more often,
>>> but so be it.
>>
>> It's just a higher frequency to avoid slowdown when bringing the link up.
> 
> No it isn't: you replaced a sleep by a delay, thus making it blocking.

For much shorter period of time.

> So this can spin for up to 50 ms (+ overhead)?

That's what it did before too , it used msleep and now it uses udelay.

>>>> --- a/drivers/pci/host/pcie-rcar.c
>>>> +++ b/drivers/pci/host/pcie-rcar.c
>>>> @@ -528,13 +528,13 @@ static void phy_write_reg(struct rcar_pcie *pcie,
>>>>
>>>>  static int rcar_pcie_wait_for_dl(struct rcar_pcie *pcie)
>>>>  {
>>>> -    unsigned int timeout = 10;
>>>> +    unsigned int timeout = 10000;
>>>>
>>>>      while (timeout--) {
>>>>              if ((rcar_pci_read_reg(pcie, PCIETSTR) & DATA_LINK_ACTIVE))
>>>>                      return 0;
>>>>
>>>> -            msleep(5);
>>>> +            udelay(5);
>>>>      }
>>>>
>>>>      return -ETIMEDOUT;
> 
> 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
> 


-- 
Best regards,
Marek Vasut