[PATCHv2] omapdrm: hdmi4_cec: Fix CEC clock handling for PM

[Tony Lindgren]

If CONFIG_OMAP4_DSS_HDMI_CEC is enabled in .config, deeper SoC idle
states are blocked because the CEC clock gets always enabled on init.

Let's fix the issue by moving the CEC clock handling to happen later in
hdmi_cec_adap_enable() as suggested by Hans Verkuil <hverkuil at xs4all.nl>.
This way the CEC clock gets only enabled when needed. This can be tested
by doing cec-ctl --playback to enable the CEC, and doing cec-ctl --clear
to disable it.

Let's also fix the typo for "divider" in the comments while at it.

Fixes: 8d7f934df8d8 ("omapdrm: hdmi4_cec: add OMAP4 HDMI CEC support")
Suggested-by: Hans Verkuil <hverkuil at xs4all.nl>
Cc: Hans Verkuil <hverkuil at xs4all.nl>
Cc: Jyri Sarha <jsarha at ti.com>
Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Signed-off-by: Tony Lindgren <tony at atomide.com>
---

Changes since v1:

- Move clock enable to happen after the whole disable section rather than
  add a pointless test for enable as noted by Hans

- Move clock enable to happen after hdmi4_core_enable() as otherwise doing
  cec-ctl --playback with no HDMI cable connected will cause imprecise
  external abort as HDMI core is idled

- Disable CEC device on possible errors

---
 drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c | 26 ++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c b/drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c
--- a/drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c
+++ b/drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c
@@ -175,6 +175,7 @@ static int hdmi_cec_adap_enable(struct cec_adapter *adap, bool enable)
 		REG_FLD_MOD(core->base, HDMI_CORE_SYS_INTR_UNMASK4, 0, 3, 3);
 		hdmi_wp_clear_irqenable(core->wp, HDMI_IRQ_CORE);
 		hdmi_wp_set_irqstatus(core->wp, HDMI_IRQ_CORE);
+		REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0, 5, 0);
 		hdmi4_core_disable(core);
 		return 0;
 	}
@@ -182,16 +183,24 @@ static int hdmi_cec_adap_enable(struct cec_adapter *adap, bool enable)
 	if (err)
 		return err;
 
+	/*
+	 * Initialize CEC clock divider: CEC needs 2MHz clock hence
+	 * set the divider to 24 to get 48/24=2MHz clock
+	 */
+	REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0x18, 5, 0);
+
 	/* Clear TX FIFO */
 	if (!hdmi_cec_clear_tx_fifo(adap)) {
 		pr_err("cec-%s: could not clear TX FIFO\n", adap->name);
-		return -EIO;
+		err = -EIO;
+		goto err_disable_clk;
 	}
 
 	/* Clear RX FIFO */
 	if (!hdmi_cec_clear_rx_fifo(adap)) {
 		pr_err("cec-%s: could not clear RX FIFO\n", adap->name);
-		return -EIO;
+		err = -EIO;
+		goto err_disable_clk;
 	}
 
 	/* Clear CEC interrupts */
@@ -236,6 +245,12 @@ static int hdmi_cec_adap_enable(struct cec_adapter *adap, bool enable)
 		hdmi_write_reg(core->base, HDMI_CEC_INT_STATUS_1, temp);
 	}
 	return 0;
+
+err_disable_clk:
+	REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0, 5, 0);
+	hdmi4_core_disable(core);
+
+	return err;
 }
 
 static int hdmi_cec_adap_log_addr(struct cec_adapter *adap, u8 log_addr)
@@ -333,11 +348,8 @@ int hdmi4_cec_init(struct platform_device *pdev, struct hdmi_core_data *core,
 		return ret;
 	core->wp = wp;
 
-	/*
-	 * Initialize CEC clock divider: CEC needs 2MHz clock hence
-	 * set the devider to 24 to get 48/24=2MHz clock
-	 */
-	REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0x18, 5, 0);
+	/* Disable clock initially, hdmi_cec_adap_enable() manages it */
+	REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0, 5, 0);
 
 	ret = cec_register_adapter(core->adap, &pdev->dev);
 	if (ret < 0) {
-- 
2.21.0