From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sam Ravnborg Subject: Re: [PATCH V7 2/2] drm/panel: Add Sitronix ST7701 panel driver Date: Sat, 12 Jan 2019 13:00:56 +0100 Message-ID: <20190112120056.GA7374@ravnborg.org> References: <20190111124714.19566-1-jagan@amarulasolutions.com> <20190111124714.19566-2-jagan@amarulasolutions.com> <20190111211931.GA29735@ravnborg.org> <20190112101409.GA14273@ravnborg.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from asavdk3.altibox.net (asavdk3.altibox.net [109.247.116.14]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3CB126E349 for ; Sat, 12 Jan 2019 12:01:00 +0000 (UTC) Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Jagan Teki Cc: David Airlie , Sean Paul , linux-kernel , dri-devel , Thierry Reding , Michael Trimarchi , linux-amarula@amarulasolutions.com List-Id: dri-devel@lists.freedesktop.org PiA+Cj4gPiA+ID4gPiArCj4gPiA+ID4gPiArICAgICBtc2xlZXAoc3Q3NzAxLT5zbGVlcF9kZWxh eSk7Cj4gPiA+ID4gPiArCj4gPiA+ID4gPiArICAgICBncGlvZF9zZXRfdmFsdWUoc3Q3NzAxLT5y ZXNldCwgMCk7Cj4gPiA+ID4gPiArCj4gPiA+ID4gPiArICAgICBncGlvZF9zZXRfdmFsdWUoc3Q3 NzAxLT5yZXNldCwgMSk7Cj4gPiA+ID4gPiArCj4gPiA+ID4gPiArICAgICBncGlvZF9zZXRfdmFs dWUoc3Q3NzAxLT5yZXNldCwgMCk7Cj4gPiA+ID4gTm8gdGltaW5nIGNvbnN0cmFpbnMgaGVyZT8g SW4gcHJlcGFyZSB0aGVyZSBhcmUgc2xlZXBzIGludGVybWl4ZWQuCj4gPiA+Cj4gPiA+IERlbGF5 IHdoaWxlIGRvaW5nIHVucHJhcmUgaXMgbm90IG5lZWRlZCBJIHN1cHBvc2UuCj4gPgo+ID4gSWYg dGhlIHB1cnBvc2UgaXMgYWxvbmUgdG8gcmVzZXQgdGhlIGRpc3BsYXkgdGhlbiBhIHNpbmdsZSB3 cml0ZSAnMCcKPiA+IHNob3VsZCBkbyBpdCBJIHRoaW5rCj4gCj4gSSBldmVuIHRyaWVkIHRoaXMg anVzdCBzZXQgMCwgc2luY2UgcHJlcGFyZSBpcyBkb2luZyBhIHNlcXVlbmNlLCBpdAo+IGdvb2Qg YmVoYXZpb3IgdG8gZG8gdGhlIHJldmVyc2UgZHVyaW5nIGhhbmRvZmYuIGllIHJlYXNvbiBJIGp1 c3QKPiBpbml0aWF0ZWQgdGhpcyBzZXF1ZW5jZS4KPiAKPiA+IEFuZCB0aGVyZSBpcyBhIHJlcXVp cmVtZW50IHRoYXQgaXQgbXVzdCBiZSBsb3cgZm9yIGEgbWluaW11bSBvZiAxMCB1cwo+ID4gd2hp Y2ggd291bGQgYmUgZ29vZCB0byBoYXZlIGhlcmUuCj4gCj4gU29ycnksIEkgZGlkbid0IGdldCB0 aGlzIHJlcXVpcmVtZW50IHdoYXQgaXMgdGhpcyBmb3I/ClRoZSBzdDc3MDEgd2lsbCBpZ25vcmUg cmVzZXQgcHVsc2Ugc2hvcnRlciB0aGFuIDEwIHVzIC0gc2VlIFRydyBpbgp0YWJsZSA5IHJlc2V0 IHRpbWluZyAocGFnZSA1NCkuCgpCdXQgYXMgd2UganVzdCBhc3NlcnQgcmVzZXQgKHNldCBpdCB0 byAwKSwgdGhpcyB0aW1pbmcgY29uc3RyYWludCBjYW4gYmUgaWdub3JlZC4KCj4gPiBJIGFzbG8g Zm91bmQgaW4gY2hhcHRlciA5LiAocGFnZSAxNjMgLSBzZWNvbmQgbGluZSkgdGhpcyBzdGF0ZW1l bnQ6Cj4gPiAiVkREQSBhbmQgVkRESSBtdXN0IGJlIHBvd2VyZWQgZG93biB3aXRoIG1pbmltdW0g MTIwbXNlYy4iCj4gCj4gWWVzIHVucHJlcGFyZSBpcyBkb2luZyB0aGUgc2FtZSwgaXQgZXhpdCBm cm9tIHNsZWVwIG91dCBtb2RlIGFuZCB3YWl0Cj4gZm9yIDEyMG1zZWMgYW5kIGRvIHRoZSByZXNl dC4KPiAKPiA+Cj4gPiBUaGlzIGlzIHNpbWlsYXIgdG8gdGhlIHVucHJlcGFyZSBkZWxheSB0byBi ZSBmb3VuZCBpbiBzaW1wbGUtcGFuZWwuYwo+ID4gU28gYW4gdW5wcmVwYXJlIGRlbGF5IHNlZW1z IGluIG9yZGVyIGhlcmUuCj4gCj4gTG9vayBsaWtlIHNpbXBsZS1wYW5lbC5jIGlzIGRvaW5nIGRl bGF5IGFmdGVyIHJlc2V0IGluaXRpYXRlZCBhbmQKPiByZWd1bGF0b3IgZGlzYWJsZWQuCgoKCVNh bQoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KZHJpLWRl dmVsIG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBzOi8v bGlzdHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJpLWRldmVsCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5A24C43387 for ; Sat, 12 Jan 2019 12:01:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A9FF520870 for ; Sat, 12 Jan 2019 12:01:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726412AbfALMBB (ORCPT ); Sat, 12 Jan 2019 07:01:01 -0500 Received: from asavdk3.altibox.net ([109.247.116.14]:41654 "EHLO asavdk3.altibox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725823AbfALMBB (ORCPT ); Sat, 12 Jan 2019 07:01:01 -0500 Received: from ravnborg.org (unknown [158.248.194.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by asavdk3.altibox.net (Postfix) with ESMTPS id 1982A20054; Sat, 12 Jan 2019 13:00:57 +0100 (CET) Date: Sat, 12 Jan 2019 13:00:56 +0100 From: Sam Ravnborg To: Jagan Teki Cc: David Airlie , linux-amarula@amarulasolutions.com, linux-kernel , dri-devel , Thierry Reding , Michael Trimarchi , Sean Paul Subject: Re: [PATCH V7 2/2] drm/panel: Add Sitronix ST7701 panel driver Message-ID: <20190112120056.GA7374@ravnborg.org> References: <20190111124714.19566-1-jagan@amarulasolutions.com> <20190111124714.19566-2-jagan@amarulasolutions.com> <20190111211931.GA29735@ravnborg.org> <20190112101409.GA14273@ravnborg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-CMAE-Score: 0 X-CMAE-Analysis: v=2.3 cv=dqr19Wo4 c=1 sm=1 tr=0 a=UWs3HLbX/2nnQ3s7vZ42gw==:117 a=UWs3HLbX/2nnQ3s7vZ42gw==:17 a=kj9zAlcOel0A:10 a=h2XvLM43PzkowCm6i1cA:9 a=CjuIK1q_8ugA:10 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > > > > > > + > > > > > + msleep(st7701->sleep_delay); > > > > > + > > > > > + gpiod_set_value(st7701->reset, 0); > > > > > + > > > > > + gpiod_set_value(st7701->reset, 1); > > > > > + > > > > > + gpiod_set_value(st7701->reset, 0); > > > > No timing constrains here? In prepare there are sleeps intermixed. > > > > > > Delay while doing unprare is not needed I suppose. > > > > If the purpose is alone to reset the display then a single write '0' > > should do it I think > > I even tried this just set 0, since prepare is doing a sequence, it > good behavior to do the reverse during handoff. ie reason I just > initiated this sequence. > > > And there is a requirement that it must be low for a minimum of 10 us > > which would be good to have here. > > Sorry, I didn't get this requirement what is this for? The st7701 will ignore reset pulse shorter than 10 us - see Trw in table 9 reset timing (page 54). But as we just assert reset (set it to 0), this timing constraint can be ignored. > > I aslo found in chapter 9. (page 163 - second line) this statement: > > "VDDA and VDDI must be powered down with minimum 120msec." > > Yes unprepare is doing the same, it exit from sleep out mode and wait > for 120msec and do the reset. > > > > > This is similar to the unprepare delay to be found in simple-panel.c > > So an unprepare delay seems in order here. > > Look like simple-panel.c is doing delay after reset initiated and > regulator disabled. Sam