From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751705AbdAPXRu (ORCPT ); Mon, 16 Jan 2017 18:17:50 -0500 Received: from mail-pg0-f45.google.com ([74.125.83.45]:34467 "EHLO mail-pg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751012AbdAPXRr (ORCPT ); Mon, 16 Jan 2017 18:17:47 -0500 From: John Stultz To: lkml Cc: John Stultz , David Airlie , Archit Taneja , Wolfram Sang , Lars-Peter Clausen , Laurent Pinchart , dri-devel@lists.freedesktop.org Subject: [RFC][PATCH] drm/bridge: adv7511: Re-write the i2c address as it may have been lost Date: Mon, 16 Jan 2017 15:16:51 -0800 Message-Id: <1484608611-10956-1-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1668382.5d9jBvLc1l@avalon> References: <1668382.5d9jBvLc1l@avalon> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Laurent: Would something like the following be preferred? Seems to work as well for me.. thanks -john I've found that by just turning the chip on and off via the POWER_DOWN register, I end up getting i2c_transfer errors on HiKey. Investigating further, it seems some of the register state in the regmap cache is somehow getting lost, likely as the device registers were reset during power off. Thus this patch simply re-writes the i2c address to the ADV7511_REG_EDID_I2C_ADDR register to ensure its properly set before we try to read the EDID data. Cc: David Airlie Cc: Archit Taneja Cc: Wolfram Sang Cc: Lars-Peter Clausen Cc: Laurent Pinchart Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz --- drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c index 405e460..32c59cb 100644 --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c @@ -567,6 +567,8 @@ static int adv7511_get_modes(struct adv7511 *adv7511, /* Reading the EDID only works if the device is powered */ if (!adv7511->powered) { + unsigned int edid_i2c_addr = (adv7511->i2c_main->addr << 1) + 4; + regmap_update_bits(adv7511->regmap, ADV7511_REG_POWER, ADV7511_POWER_POWER_DOWN, 0); if (adv7511->i2c_main->irq) { @@ -576,6 +578,9 @@ static int adv7511_get_modes(struct adv7511 *adv7511, ADV7511_INT1_DDC_ERROR); } adv7511->current_edid_segment = -1; + + /* Reset the EDID_I2C_ADDR register as it may have been cleared */ + regmap_write(adv7511->regmap, ADV7511_REG_EDID_I2C_ADDR, edid_i2c_addr); } edid = drm_do_get_edid(connector, adv7511_get_edid_block, adv7511); -- 2.7.4