From mboxrd@z Thu Jan 1 00:00:00 1970 From: Felipe Balbi Subject: Re: [RFC PATCH v2 08/15] usb:cdns3: Implements device operations part of the API Date: Fri, 14 Dec 2018 13:26:02 +0200 Message-ID: <875zvwl585.fsf@linux.intel.com> References: <1542535751-16079-1-git-send-email-pawell@cadence.com> <1542535751-16079-9-git-send-email-pawell@cadence.com> <5BFE8883.7090802@ti.com> <6b19b55c-66d7-439e-df8f-7b311b45af5e@ti.com> <5a41de27-cd1f-0cfd-ccdc-dccbf0854fcb@ti.com> <87bm5ol6zt.fsf@linux.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Sekhar Nori , Peter Chen , pawell@cadence.com Cc: rogerq@ti.com, devicetree@vger.kernel.org, Greg Kroah-Hartman , linux-usb@vger.kernel.org, lkml , adouglas@cadence.com, jbergsagel@ti.com, nm@ti.com, sureshp@cadence.com, peter.chen@nxp.com, pjez@cadence.com, kurahul@cadence.com List-Id: devicetree@vger.kernel.org --=-=-= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi, Sekhar Nori writes: >>>>>> All this should be part of comments in code along with information a= bout >>>>>> controller versions which suffer from the errata. >>>>>> >>>>>> Is there a version of controller available which does not have the >>>>>> defect? Is there a future plan to fix this? >>>>>> >>>>>> If any of that is yes, you probably want to handle this with runtime >>>>>> detection of version (like done with DWC3_REVISION_XXX macros). >>>>>> Sometimes the hardware-read versions themselves are incorrect, so its >>>>>> better to introduce a version specific compatible too like >>>>>> "cdns,usb-1.0.0" (as hinted to by Rob Herring as well). >>>>>> >>>>> >>>>> custom match_ep is used and works with all versions of the gen1 >>>>> controller. Future (gen2) releases of the controller won=E2=80=99t ha= ve such >>>>> limitation but there is no plan to change current (gen1) functionality >>>>> of the controller. >>>>> >>>>> I will add comment before cdns3_gadget_match_ep function. >>>>> Also I will change cdns,usb3 to cdns,usb3-1.0.0 and add additional >>>>> cdns,usb3-1.0.1 compatible. >>>>> >>>>> cdns,usb3-1.0.1 will be for current version of controller which I use. >>>>> cdns,usb3-1.0.0 will be for older version - Peter Chan platform. >>>>> I now that I have some changes in controller, and one of them require >>>>> some changes in DRD driver. It will be safer to add two separate >>>>> version in compatibles. >>>>> >>>> >>>> Pawel, could we have correct register to show controller version? It is >>>> better we could version judgement at runtime instead of static compati= ble. >>> >>> Agree with detecting IP version at runtime. >>> >>> But please have some indication of version in compatible string too, >>=20 >> why? Runtime detection by revision register should be the way to go if >> the HW provides it. Why duplicate the information in compatible string? >>=20 >>> especially since you already know there is going to be another revision >>> of hardware. It has the advantage that one can easily grep to see which >>> hardware is running current version of controller without having access >>> to the hardware itself. Becomes useful later on when its time to >>> clean-up unused code when boards become obsolete or for requesting >>> testing help. >>=20 >> This doesn't sound like a very strong argument, actually. Specially when >> you consider that, since driver will do revision checking based on >> revision register, you already have strings to grep. Moreover, we don't >> usually drop support just like that. > > AFAICS, it is impossible to know just by grep'ing if there is any > hardware still supported in kernel and using DWC3_REVISION_194A, for > example. but why do you even care?=20 > If we are never going to drop support for any revision, this does not > matter much. > > Also, once you have the controller supported behind PCI, then I guess > you are pretty much tied to having to read hardware revision at runtime. that's another argument *for* using runtime detection, not against it. =2D-=20 balbi --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEElLzh7wn96CXwjh2IzL64meEamQYFAlwTk0oACgkQzL64meEa mQYA5w/9FY3dE8D+YHmrb3tnHyR6vwaTBRUsHcVyJ1J0yspewdcd/07/VcXfnD28 ebvRVP4Idebgch5S9J/CRMYE1LAn/SMDYyZshye/iuOv1SMReVaPo9YW5/hFPKGX r8BfKhE/4qHMVWeTN1euiYr8iTtPldBcZ+1R3+JxDyYqFL8XD0c6bgeVrHfSBBBn CrqqAn6boJCurIAQ7DpRhrN84hz4zI5dbRM5vAvEWerqjxl2LU3ADvX6KQzSM81J BqdIo6ucOok3FAlhg9OVeA+IceRMjdvHFisN1Tlcqu2ZmacneGZuNvQ1/0l7B6Th ciDraD8jWbIYxCl/m9tmLPC8qx6Od5o4s19ZYCBwVtgJTTypzIC1c3MHcD6a3rcG WOlT7kPB7xr2H8UUXmd3l6ZzOFrJpLPfQPihvQNt6Uy3aQjt4WXvYiIyS8XciXkn 8TduIbwJ0mAuivKrTBOUGWE6oCMnJs8x2oz+Ytoli9FkhxgXsfWhYBgZlLcZB6nT h5Obm7VtLAaskRpSe4vIV/Wg4Qac7OcjYL4WytDuL79A6py05DZ5kigxLUfToPyF OPcwGHAOjri82WZIDzksQY9hB7yBuxAWGL6tERnamRtxCN1qIczzxlTttQq5dF4q 4hV2JhbROuNDETAUzAS6c8ypj0+d/ngF75m/vhsqr23J8SEkYjk= =hfQv -----END PGP SIGNATURE----- --=-=-=--