Message-ID: <97f3c6e0ec70c4284a4ddfb86d6b0592@posteo.net>
Date:   Wed, 21 Jun 2023 22:21:28 +0000
From:   Anne Macedo <retpolanne@...teo.net>
To:     Christian Lamparter <chunkeey@...il.com>
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Vinod Koul <vkoul@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: host: xhci: parameterize Renesas delay/retry



On 21.06.2023 22:20, Christian Lamparter wrote:
> On 6/19/23 12:12, Anne Macedo wrote:
>> On 19.06.2023 10:19, Christian Lamparter wrote:
>>> On 6/19/23 00:46, Anne Macedo wrote:
>>>> Cards based on Renesas uPD720202 have their firmware downloaded 
>>>> during
>>>> boot by xhci-pci. At this step, the status of the firmware is read 
>>>> and
>>>> it takes a while for this read to happen (up to a few seconds). The
>>>> macros RENESAS_RETRY and RENESAS_DELAY are used to retry reading 
>>>> this
>>>> status byte from PCI a few times. If it can't read the status byte 
>>>> in
>>>> RENESAS_RETRY tries, it times out.
>>>> 
>>>> However, since this may vary from card to card, these retry and 
>>>> delay
>>>> values need to be tweaked. In order to avoid having to patch the 
>>>> code to
>>>> change these values, CONFIG_USB_XHCI_PCI_RENESAS_RETRY and
>>>> CONFIG_USB_XHCI_PCI_RENESAS_DELAY are introduced.
>>>> 
>>>> If applied, this patch helps to fix errors such as:
>>>> 
>>>> ROM Download Step 34 failed at position 136 bytes
>>>> Firmware Download Step 2 failed at position 8 bytes with (-110)
>>>> 
>>>> while loading xhci-pci when using these cards.
>>>> 
>>>> This error in particular has been noticed by this e-mail [1].
>>>> 
>>>> [1] https://lore.kernel.org/lkml/20190626070658.GP2962@vkoul-mobl/
>>> 
>>> Can you tell me on what hardware (is it something older, with maybe
>>> a Synopsys/Designware PCIe host controller?) do you experience these
>>> errors and what delay+retry values are you configuring in order to
>>> get your DUT up an running?
>> 
>> It's a PH61 Rev 1.2 board with the Renesas uPD720201 host controller.
>> I'm using 10 as the delay and 6000 as the retry.
> 
> Oh? Is this an old MSI PH61 mainboard or is this an add-in pcie card
> (found something on amazon with that name and rev too)?

It's the add-in pcie card, exactly the one that's available on Amazon.

> 
> If it's an add-in pcie card, could it be that the EEPROM chip on it
> is (getting) a bit wonky? Or do you have a really fast machine?
> (Latest crop of i7/i9 Alder/Raptor Lake or Ryzen 5000/7000 Series)
> 

I do have a fast machine, but I believe the EEPROM chip might have gone 
wonky
for sure. It was the first card I found on my local retailer for adding 
USB-C
headers to my setup.


>>> From what I can tell, the quoted [1] link to Vinod's mail was just
>>> an update during development. This was v3 of the patch series back
>>> then (and it went on to v10 I think, so this wasn't an issue with
>>> what's in the kernel right now).
>>> 
>> 
>> I see. That was the only reference I found to the timeout error I was
>> seeing, so that's why I decided to tweak these retry+delay values.
>> 
>>> Note: If you are interested I still got the "uPD720201/uPD720202 
>>> User's
>>> Manual" back then from Renesas site. (Nowadays they want you to
>>> register or something.). This document was the base for the code and
>>> maybe there's something in there you can quote to extend the
>>> retries/delays.
>> 
>> Definitely interested! I did find a .pdf on Google though, I can check 
>> it.
> 
> There's also Renesas loader code floating around on github.

ACK - I believe I saw this one as well.

> 
>>> 
>>> (From what I vaguely remember. Most of the transfer was fast and
>>> no retries where necessary, but some register write took so long.
>>> Vinod  also posted hints about a newer firmware for the
>>> uPD720201/uPD720202. Have you tried that as well?)
>> 
>> I was using the upd72020x-fw AUR package on my Arch Linux build,
>> if that's any relevant. However, it's quite old and I don't really 
>> know
>> how it works. I missed these hints, sorry, could you point me to
>> them?
> 
> Yes, I was talking about "K2026090.mem". I didn't know this version 
> existed,
> but Vinod knew about it:
> https://patches.linaro.org/project/linux-arm-msm/patch/20200113084005.849071-5-vkoul@kernel.org/
> 
> Looking on google leads to startech.com and they have/had this as a 
> product:
> https://www.startech.com/en-de/cards-adapters/pciusb3s22
> 
> The K2026090.mem Firmware file is in the "[renesas upd72020x] firmware
> update.zip"
> (see in the "RE202.A10" folder).

Will try that!

> 
> I don't know how it works with pcie cards that are supposed to have the 
> firmware
> stored on the EEPROM chip. In my case of the WNDR4700 - there is no
> extra chip and
> the driver has to upload the firmware - I just have to put the file 
> renamed as
> renesas_usb_fw.mem into /lib/firmware/ and it works.
> 

I wrote a bpf program to trace the PCI read/write calls from this 
specific Renesas
device [1]. On the manual you mentioned, there's a step on the firmware 
download
where a register is changed when the firmware download finishes. On my 
bpftrace,
I see that it takes a long while for it to actually change, so I'm not 
sure what could be
the problem.

I also wrote a patch for my dev environment to allow me to erase the ROM 
as needed [2], but
it hangs for a long time as well until the timeout is reached.

I *think* that the kernel module erases the ROM at some point when 
starting up and then polls
if the ROM has been reset.

I've been thinking about Greg's suggestion of setting this timeout 
dynamically, and I was taking
a look at different ways to deal with waiting and timeouts on kernel 
modules. Do you think it's
worth it to implement something like a better waiting logic for this 
module?

I didn't find anything on the card and in the manual that could point me 
to a way of discovering
how long to set the timeout on it.

[1] 
https://github.com/retpolanne/kernel-workspace/blob/main/bpf/renesas-pci-trace.bt
[2] 
https://github.com/retpolanne/kernel-workspace/blob/main/patches/erase-rom.patch
> Regards,
> Christian

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