Re: [PATCH 1/2] PCI: rcar: Poll more often in rcar_pcie_wait_for_dl()

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Hi Marek,

On Mon, Mar 19, 2018 at 10:53 AM, Marek Vasut <marek.vasut@xxxxxxxxx> 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@xxxxxxxxx>
>>> Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>>> Cc: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
>>> Cc: Simon Horman <horms+renesas@xxxxxxxxxxxx>
>>> Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
>>> Cc: linux-renesas-soc@xxxxxxxxxxxxxxx
>>
>> 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.
So this can spin for up to 50 ms (+ overhead)?

>>> --- 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@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



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