linux-kernel - [PATCH 4/5] media: atomisp: change clock source default for ISP2401

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Date:   Thu,  4 Jun 2020 22:47:04 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-media@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] media: atomisp: change clock source default for ISP2401

There's a notice there stating that the PLL is not reliable
for CHT. Yet, it tries to read it via the BIOS. Well,
this will fail (at least with the devices I checked the
DSDT tables). So, change the logic in a way that it will
change the default, depending on the ISP version.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
---
 .../media/atomisp/pci/atomisp_gmin_platform.c  | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
index cb02806274d1..a14326111b26 100644
--- a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
+++ b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
@@ -493,9 +493,23 @@ static struct gmin_subdev *gmin_subdev_add(struct v4l2_subdev *subdev)
 
 	gmin_subdevs[i].subdev = subdev;
 	gmin_subdevs[i].clock_num = gmin_get_var_int(dev, false, "CamClk", 0);
-	/*WA:CHT requires XTAL clock as PLL is not stable.*/
+	/*
+	 * FIXME:
+	 * 	WA:CHT requires XTAL clock as PLL is not stable.
+	 *
+	 * However, such data doesn't seem to be present at the _DSM
+	 * table under the GUID dc2f6c4f-045b-4f1d-97b9-882a6860a4be.
+	 * So, let's change the default according with the ISP version,
+	 * but allowing it to be overridden by BIOS or by DMI match tables.
+	 */
+	if (IS_ISP2401)
+		gmin_subdevs[i].clock_src = VLV2_CLK_XTAL_25_0MHz;
+	else
+		gmin_subdevs[i].clock_src = VLV2_CLK_PLL_19P2MHZ;
+
 	gmin_subdevs[i].clock_src = gmin_get_var_int(dev, false, "ClkSrc",
-				    VLV2_CLK_PLL_19P2MHZ);
+						     gmin_subdevs[i].clock_src);
+
 	gmin_subdevs[i].csi_port = gmin_get_var_int(dev, false, "CsiPort", 0);
 	gmin_subdevs[i].csi_lanes = gmin_get_var_int(dev, false, "CsiLanes", 1);
 
-- 
2.26.2