linux-kernel - [PATCH v2 17/17] soundwire: cadence: clear FIFO to avoid pop noise issue on playback start

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Message-Id: <20200317163329.25501-18-pierre-louis.bossart@linux.intel.com>
Date:   Tue, 17 Mar 2020 11:33:29 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     alsa-devel@...a-project.org
Cc:     linux-kernel@...r.kernel.org, tiwai@...e.de, broonie@...nel.org,
        vkoul@...nel.org, gregkh@...uxfoundation.org, jank@...ence.com,
        srinivas.kandagatla@...aro.org, slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Hui Wang <hui.wang@...onical.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: [PATCH v2 17/17] soundwire: cadence: clear FIFO to avoid pop noise issue on playback start

From: randerwang <rander.wang@...ux.intel.com>

Driver should clear FIFO in PDI, or the previously stored sample data
in FIFO will generate pop noise when stream is started. The soft reset
bit will clear all the FIFO to zero and is self-cleared after that.

Signed-off-by: randerwang <rander.wang@...ux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
---
 drivers/soundwire/cadence_master.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index eedc4cefdab0..ecd357d1c63d 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -1503,6 +1503,7 @@ void sdw_cdns_config_stream(struct sdw_cdns *cdns,
 	cdns_updatel(cdns, offset, CDNS_PORTCTRL_DIRN, val);
 
 	val = pdi->num;
+	val |= CDNS_PDI_CONFIG_SOFT_RESET;
 	val |= ((1 << ch) - 1) << SDW_REG_SHIFT(CDNS_PDI_CONFIG_CHANNEL);
 	cdns_writel(cdns, CDNS_PDI_CONFIG(pdi->num), val);
 }
-- 
2.20.1