Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934226AbcKVTq4 (ORCPT ); Tue, 22 Nov 2016 14:46:56 -0500 Received: from mail-oi0-f47.google.com ([209.85.218.47]:36771 "EHLO mail-oi0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932661AbcKVTqz (ORCPT ); Tue, 22 Nov 2016 14:46:55 -0500 MIME-Version: 1.0 In-Reply-To: <1661379.b8y5I25JKx@avalon> References: <1479775052-28194-1-git-send-email-john.stultz@linaro.org> <1961666.AZMl081OYz@avalon> <1661379.b8y5I25JKx@avalon> From: John Stultz Date: Tue, 22 Nov 2016 11:46:53 -0800 Message-ID: Subject: Re: [RFC][PATCH 1/3] drm/bridge: adv7511: Rework adv7511_power_on/off() so they can be reused internally To: Laurent Pinchart Cc: lkml , David Airlie , Archit Taneja , Wolfram Sang , Lars-Peter Clausen , "dri-devel@lists.freedesktop.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3828 Lines: 92 On Tue, Nov 22, 2016 at 9:38 AM, Laurent Pinchart wrote: > Hi John, > > On Tuesday 22 Nov 2016 09:25:22 John Stultz wrote: >> On Tue, Nov 22, 2016 at 12:14 AM, Laurent Pinchart wrote: >> > On Monday 21 Nov 2016 16:37:30 John Stultz wrote: >> @@ -545,24 +554,13 @@ static int adv7511_get_modes(struct adv7511 *adv7511, >> >> unsigned int count; >> >> >> >> /* Reading the EDID only works if the device is powered */ >> >> >> >> - if (!adv7511->powered) { >> >> - regmap_update_bits(adv7511->regmap, ADV7511_REG_POWER, >> >> - ADV7511_POWER_POWER_DOWN, 0); >> >> - if (adv7511->i2c_main->irq) { >> >> - regmap_write(adv7511->regmap, >> >> ADV7511_REG_INT_ENABLE(0), >> >> - ADV7511_INT0_EDID_READY); >> >> - regmap_write(adv7511->regmap, >> >> ADV7511_REG_INT_ENABLE(1), >> >> - ADV7511_INT1_DDC_ERROR); >> >> - } >> >> - adv7511->current_edid_segment = -1; >> >> - } >> >> + if (!adv7511->powered) >> >> + __adv7511_power_on(adv7511); >> > >> > The __adv7511_power_on() function does more than the above, in particular >> > it performs an expensive regcache_sync() and calls adv7533_dsi_power_on() >> > for the ADV7533. Don't those operations have side effects that are either >> > not wanted or not needed here ? In any case this patch modifies the >> > behaviour of the driver, which needs to be documented in the kernel >> > message. >> >> So yes, while the adv7533 bits aren't needed in the internal function, >> I'm finding the logic to pulse the HPD and the regcache_sync call seem >> to be needed side effects, as without that logic, I get i2c_transfer() >> errors in adv7511_get_edid_block(). > > Does this patch fix the problem without requiring the 200ms delay ? > >> I'll try to rework this patch to split the two changes of reworking >> the power_on/off function to be re-used (with no logic chage), and the >> patch to reuse it in get_modes() which resolves a bug. > > Have you identified which register write fixes your problem here ? So I basically used regmap_sync_region() to bisect through the registers to try to figure out which one calling sync on helps avoid the issue, and I've narrowed it down to 0x43 (ADV7511_REG_EDID_I2C_ADDR). If instead of the proposed patch here, I use the following patch (copy/paste whitespace damage, apologies) seems to make things work reliably: diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c index 8dba729..87403d7 100644 --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c @@ -555,14 +557,18 @@ static int adv7511_get_modes(struct adv7511 *adv7511, ADV7511_INT1_DDC_ERROR); } adv7511->current_edid_segment = -1; + regcache_sync_region(adv7511->regmap, 0x43, 0x43); + } edid = drm_do_get_edid(connector, adv7511_get_edid_block, adv7511); - if (!adv7511->powered) + if (!adv7511->powered) { regmap_update_bits(adv7511->regmap, ADV7511_REG_POWER, ADV7511_POWER_POWER_DOWN, ADV7511_POWER_POWER_DOWN); + regcache_mark_dirty(adv7511->regmap); + } kfree(adv7511->edid); adv7511->edid = edid; But I suspect this isn't a proper fix. I tried adding ADV7511_REG_EDID_I2C_ADDR to the volatile register list, but that didn't seem to effect anything (and I still see problematic behavior if I'm not explictly syncing it as above). Thoughts on what the right thing is to do? -john