From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomi Valkeinen Date: Thu, 13 Sep 2012 06:22:57 +0000 Subject: Re: [PATCH v6 1/4] Runtime Interpreted Power Sequences Message-Id: <1347517377.7471.23.camel@lappyti> MIME-Version: 1 Content-Type: multipart/mixed; boundary="=-ZLX1dizWK3K7XKAr9srU" List-Id: References: <1347443867-18868-1-git-send-email-acourbot@nvidia.com> <1347443867-18868-2-git-send-email-acourbot@nvidia.com> <1347515139.7471.7.camel@lappyti> <1464760.6eqxJ2IzZ2@percival> In-Reply-To: <1464760.6eqxJ2IzZ2@percival> To: Alex Courbot Cc: Stephen Warren , Thierry Reding , Simon Glass , Grant Likely , Rob Herring , Mark Brown , Anton Vorontsov , David Woodhouse , Arnd Bergmann , Leela Krishna Amudala , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fbdev@vger.kernel.org" , "devicetree-discuss@lists.ozlabs.org" , "linux-pm@vger.kernel.org" , "linux-doc@vger.kernel.org" --=-ZLX1dizWK3K7XKAr9srU Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2012-09-13 at 15:08 +0900, Alex Courbot wrote: > On Thursday 13 September 2012 13:45:39 Tomi Valkeinen wrote: > > * PGP Signed by an unknown key > >=20 > > On Wed, 2012-09-12 at 18:57 +0900, Alexandre Courbot wrote: > >=20 > > > Some device drivers (panel backlights especially) need to follow prec= ise > > > sequences for powering on and off, involving gpios, regulators, PWMs > > > with a precise powering order and delays to respect between each step= s. > > > These sequences are board-specific, and do not belong to a particular > > > driver - therefore they have been performed by board-specific hook > > > functions to far. > >=20 > >=20 > > The sequences are not board-specific, they are device (backlight, etc.) > > specific. The sequences have been handled in board-specific hook > > functions so far because there hasn't been proper drivers for the > > devices. > >=20 > > If I were to take the same panel (and backlight) you have and install i= t > > on my board, I would need the same power sequence. >=20 > You could also have power sequences that control a set of GPIOs for an= =20 > external interface (and would then be more board-specific), but you are r= ight=20 What do you mean with "external interface"? But it's true that there can always be interesting board specific hardware designs, and they truly are board specific. In my experience these are quite rare, though, but perhaps not so rare that we wouldn't need to care about them. However, I fear these board specific things may be quite a bit anything, so it may well be pwm, gpios and regulators are not enough for them. For example, there could be an FPGA on the board which requires some configuration to accomplish the task at hand. It could be rather difficult to handle it with a generic power sequence. So I guess what I'm saying is that mostly these issues are device specific, and when they are not, they may be rather complex/strange and require c code. Tomi --=-ZLX1dizWK3K7XKAr9srU Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAABAgAGBQJQUXvBAAoJEPo9qoy8lh71soMP/Rib3XaxlW/uQO5zmE/8O0FK JGxO9Ci+/2DhWR+x/IHSARaEvB1NjaZmrtrTAhwB7UBYgq2ZmExbAV0/6ixDJeJI GvaCNrmTPoutNujJ3XHZwpT6fMIY3Td14Jxg0q0aTCFH34bPolXAYGVE7AdE25FU rwruxl4hIJcgnyKnjEQ5Xw9reDiT40eSDf9tRA1X7qLrM9hiJL08ECGWcDZZrnGc /+XpQDA52IGDieVaE44G0A8iQCxeQgvEjNQ+bfmJyt1oORghMrktDOEe7Aw72owX zp0PRaIPL8lUKUAIHpGJirEsp+O1iIP+azQpGQePgzMwjSIkaL36ZPw5Nzrybrhb TpDvBE9axriVm1vqGdQ/lr75YIdkaclqkc87/C9flwdIofRGWH8V+MUnyFYrM/Yo wlYDRpG0LGkEap8YXReCSBQCtBTDSRqh6Hz/MOz1rImgEYTHyAlytKUOs0SenvoZ 0AaYdPpRXPZFPbSr90VBOC+EcjuLS4MXO7R1OSrSvTONIGFMeJh867YCTpqQIHDh 2/2j4kaOEnLNcc8/QbNOxDGjNL+rekMrrFqWhdu0NZUsOb++V3NOrgxhF/3vOekr eoVDMPAnMCDPrgG66TD+gENJQw6hTRDHz51VXAVXSk51C1AE9cAno8tjGuTSmNnM a6tn51n+5MBawclaO/Zx =7oms -----END PGP SIGNATURE----- --=-ZLX1dizWK3K7XKAr9srU--