From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH] drm: Change link order to load modules first Date: Fri, 27 Jun 2014 07:14:39 +0200 Message-ID: <20140627051438.GA9258@ulmo> References: <1403486076-1397-1-git-send-email-ezequiel@vanguardiasur.com.ar> <20140623145809.GC16725@ulmo> <20140623152909.GA16870@arch.cereza> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1521784230==" Return-path: Received: from mail-we0-f172.google.com (mail-we0-f172.google.com [74.125.82.172]) by gabe.freedesktop.org (Postfix) with ESMTP id 282AF7207C for ; Thu, 26 Jun 2014 22:14:43 -0700 (PDT) Received: by mail-we0-f172.google.com with SMTP id u57so4528339wes.17 for ; Thu, 26 Jun 2014 22:14:42 -0700 (PDT) In-Reply-To: <20140623152909.GA16870@arch.cereza> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Ezequiel Garcia Cc: dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org --===============1521784230== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ikeVEW9yuYc//A+q" Content-Disposition: inline --ikeVEW9yuYc//A+q Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 23, 2014 at 12:29:09PM -0300, Ezequiel Garcia wrote: > Hi Thierry, >=20 > Thanks for looking at this. >=20 > On 23 Jun 04:58 PM, Thierry Reding wrote: > > On Sun, Jun 22, 2014 at 10:14:36PM -0300, Ezequiel Garcia wrote: > > > Given panels and I2C-connected encoders are required by DRM drivers, > > > we need to change the link order so these are probed first. This comm= it > > > moves all the i2c, panel and bridge helper drivers so they are probed > > > before the DRM drivers. > >=20 > > No. We don't need to change the link order. >=20 > Could you clarify why? I guess you have some case in mind where changing > the link order breaks things or makes something mis-behave. I said we don't need to change the link order because there is a better mechanism in the kernel to handle this type of situation. Saying "we need to change" makes it sound like there's a bug that needs to be fixed by changing the link order. That's not so. If link order breaks some drivers then its those drivers that are broken. > > What we need to do is make > > sure that modules deal properly with situations where their resources > > aren't available yet (i.e. EPROBE_DEFER). There are factors other than > > link order that influence probe ordering. > >=20 >=20 > While I understand defering is more robust, it would be systematically > defering the probe when the DRM driver needs an I2C encoder. >=20 > Just to name one example, the tilcdc, armada and others requiring TDA998x > encoder will always defered the probe of the DRM, and then re-probe() once > the encoder is ready. >=20 > So, unless we have a good reason not to do this, it sounds a bit silly > to me. The problem that I have with working around this issue by changing the link order is that it hides bugs in drivers. It's not like probe deferral is a very expensive operation, so I very much prefer this as a way of forcing drivers to be fixed rather than optimizing for a few microseconds of boot time. Also note that even if TDA998x is probed first that doesn't mean the probe will succeed. It could equally well be deferred. Thierry --ikeVEW9yuYc//A+q Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBAgAGBQJTrP2+AAoJEN0jrNd/PrOhGw8P/jhEXgLy5O7UCIvnuiIg9/hW VPplw4x/ct4XW+m9Ww+b5f4w8vnbUcG9wwngEaxAib17SaFTVRW/h7pzKIzDzCEf IkMxwYckmgdJdbM0x7lEckqv7psdJg0I6Cggx8egdeuryGNowe7zpyaYXhU2+sa3 zXWN7+CQI3xv9e2f5sW2kCTCqhekYJ7rcyFHkZUiJ9Bk9nL0VXX1wyHFOCtp37QZ +MK8DmcTY+QG2p/iqa9BIGl6QKNCe+cVBNtsTDCryApVM3qaM5/KB9Juxn8fngZo Zar4CCHiP7KRaDYt6+8j80kxxZ0bPls2mHIiOTLb+9V9EUaVHpkOzfqO0xn58eGf d+/XNu13ZaZRA5k25eUE7MuUSNdZnFEJH5O7upY8b/eh/HF2dFD/0M+5P3AbmYWL s/rOiAbd8o6IQjHYJSMtTRKh1YgrCl5xZzshSD8MygqJ1b821B2InvNNZqGF5wTt KnVZPJzv+mG5/PBNg4k+hG61f1VVPQI1TQeat5PSrSkhCkYbluGJFJjru7moKIqj Zfyd+O7Bhmr3q5MkGc1n7EE+Br0u2Dh2gr5GkhtyETsLVwhhyb6mCHYAPjYEfi7b PJOREbg2TiDSoN8CXVe0dc+2Y7QbJPZg22QC1spPtG4xI/hKR3OqaXil3TlEiI+n yfTc9t95W92ClPPl2lRi =xPmE -----END PGP SIGNATURE----- --ikeVEW9yuYc//A+q-- --===============1521784230== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel --===============1521784230==--