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Re: [Xen-devel] [GSOC-2019] Problem with initializing crossbar on bb-x15 in dom0


  • To: Julien Grall <julien.grall@xxxxxxx>, Iain Hunter <drhunter95@xxxxxxxxx>
  • From: Denis Obrezkov <denisobrezkov@xxxxxxxxx>
  • Date: Sat, 6 Jul 2019 19:55:12 +0200
  • Autocrypt: addr=denisobrezkov@xxxxxxxxx; prefer-encrypt=mutual; keydata= mQMuBFrAxPQRCAD59CJNd5LF1VmojUBpdr/bJ2TaKC7SW4ln7+PWn+QyAJfFOVFlTRIDsAlP 65y7CacXFCXmLTACo4a7HEhRb5787kPm6rc30zpL+04uXCeTruYZi0ZnQVXOiab/qy3aMsk0 6n9hMY28TSbM9nynnlrbg9pGkb1EiFVNsowJjFSKXa3Rpogte9qxfXmLf2eV0MZNnrmq6Kb2 8ri5/Ffh5DG1CsN/dkv8n1kw2QqMM2RT+ZS57D+yCehtw355EXSVh2r+GsXAqMinOexcdYI4 skvvP84OovRMnlJhmRdnbjO+QFiOVeLUj7WHMT3AbClaBlUuHkbFi9HLBHAiu6uMrNtzAQD9 KoM6SXbuvlhCq2v78dGkex9EgaA7CSnBcNXuUdrjYQf+MsZgI7oDihT6TUBO0IDQL+qSrozs /hHV+HhWtc5+SYTsHXxnTkcVe12vR0uPw3fFUuncWnMRzHivKZC2ZF/w3LJL/nGzguAoPa9e VghM38EP49yO6ESthD4WvELMy2+zPkMiUqilMfxOl370RXxEBUIzFSpP6oqvNq7fvThGTQah mrFhflGSyMHXk75VkCiY+cbrMeB9xG7H3nlbQ9fYVCOPejnt8gImeazdIghQh1tjbNpjQhy8 50klCowN5H+gaSZsy4K7jlJ1UNFz/vWCvlr3W8o4tA6EoJ4tjJV2HXcrUBPYLwkruKnv8QJM vyVj5an6Sfuwt/AmFEOKo1QJnAf+Oi47RrOmec8lXS/06TMn7z6krmuRul03HXayCtREqMyY VCf87oMpPYYnFJolDrSB8kCSZRn2aixzHl4IIGa9RVuywChzUvgZJbFGPFR+Qz1BK9Ltl7FC rQcuAqg3A2RJ7uoTNiZDfI0tKWm8BEUe5LqZqgFTkTkuV9D6UveYnDk2zUFGlDTguagW2XWI wiGaA9Ud7UBBlQGTZUwNGahAErUHI5gDSNfWEUaRBEccWKgddK3a/NhkxOveqDWWFcAt4K/g JOqBs+7Bm0RjQa+4EAP6gFx4098XBZP9ff6pPuFWRN6fvfdBDUMHqb3i2SGDWVPrRR/x+Iz/ yfjdWlC/87QoRGVuaXMgT2JyZXprb3YgPGRlbmlzb2JyZXprb3ZAZ21haWwuY29tPoiWBBMR CAA+FiEExuZY9Y+VSLigQ/5M+4kLEySe7PkFAlrAxPQCGyMFCQWjmoAFCwkIBwIGFQgJCgsC BBYCAwECHgECF4AACgkQ+4kLEySe7PleSQEAktULi71pVGKh0vykq0wrn6IyqXx1SLFNwLcr PnZ2N5gA/3Ipzf3vXWXWCwRR07BB/H+9XgqWRl3jsu5EL9TzmyFAuQINBFrAxPQQCADaIOKd +PPUX4GvjdLikKxHsFRRpk75LiFZJcFU8cCA0M4Dg/Q0LcSX82TfgrfU34y7/rrF4ig/Dj81 H8MB2u01lYA2QpQ/XdHfwFMxkj5FCB4Cq6EqGxsXsaRhw4Qu3ouiJiHCEeoMoloBLOlqpXBf qnJSnBXYJDnlyvxoFIVpX4l+q2xJk/877otbPK5TBYdeHQv/f7cWNxIUT5Feth9DVq4B9OG1 BgOA1gH13KUmWhMaO+k/rYCJd9UiRoGm7FihyWrsRnG5K6VNnLjwjMjxDukNxdlITVbeK5/E QaiKRGRcTp3OwfHy6HlQH/JXGGyfmEx0rKVjoW/DD76MPpk/AAMFB/0SBNOW9asG5HeRKhJm QOPJDwNQik4t8uuZb7mw6+QoQuyzMBkXvhL7Aud0OluPeSYL2jZPw2IB26gvlUVva+FJRW9X 7cInI5mnuB4HBGdNpzR+ngRzFyf+qsd6cUrrioQUQozQKCgKG/J2LimV1fC4hQW0n5Q0qM9I KX3PtRCgxItQbn/HdqkTXqv8oxDB9cQILJvIYDZnVLojB4rJFUNb397ao3qaXdXj3iaX6wwJ 2Oo3cSxMGdY/8grRTDGYjItpWEM2noIRzdWSybzavtLHu/LmG4rbgy2aNm/TiVp28G5KvWW/ fCLomZhN0JscRgSkYjSaxmMgEdks1h9DWTHkiH4EGBEIACYWIQTG5lj1j5VIuKBD/kz7iQsT JJ7s+QUCWsDE9AIbDAUJBaOagAAKCRD7iQsTJJ7s+UF2AQDqHEO2tekVMTWJa3SakIM5FJjk sao+JkzbKe0vDy4ecwEAukGaHvmKxMZsUOOjDWjDe4eV+aRTVjUjY7LAl3OJkiU=
  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, nd <nd@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Hunyue Yau <hy-gsoc@xxxxxxxxxxxxxxx>
  • Delivery-date: Sat, 06 Jul 2019 17:55:22 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

Hi,

On 7/6/19 7:37 PM, Julien Grall wrote:

> 
> Yes it would be sensible to try to implement a crossbar driver in Xen
> and test with the UART. Looking at the driver in Linux, this should not
> be too difficult.
I don't understand why xen doesn't react on triple Ctrl+a. It probably
means that UART's interrupts doesn't work. But I was able to type in
u-boot so the uart should be already configured. Or not? Should I set up
it in a crossbar first?
> 
>>>
> 
> I don't think I ever suggested to not expose the crossbar to Dom0.
> Instead, I suggested to virtualize for Dom0, so it can be used by Xen as
> well.
> 
>>>
>>>> Also, the tegra
>>>> implementation blacklist only a uart.
>>>
>>> I don't understand this.
>> In here [1] you can find that only uart is blacklisted (in
>> tegra_blacklist_dev[]). So, in tegra they didn't blacklist their version
>> of the crossbar.
> 
> This series has not been merged. In other word, the code is not yet
> matching the expectations of the maintainers.
> 
> I pointed you to this series, because I think some of the idea could be
> re-used for implementing the crossbar.
> 
> In this particular case, it has been suggested to use blacklist_dev
> rather than unmapping (see [2]).
> 

Hm, I thought that idea behind the patch was that they unmap the control
register and intercept the calls from Linux to that control register. At
the same time they preserved the crossbar in the device tree. And, I
thought that you wanted to demonstrate this exact thing. Could you
describe how in general the approach with blacklisting should work?

-- 
Regards, Denis Obrezkov

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