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[v2,01/13] media: i2c: imx214: Fix link frequency

Message ID 20241021-imx214-v2-1-fbd23e99541e@apitzsch.eu (mailing list archive)
State New
Headers show
Series media: i2c: imx214: Miscellaneous cleanups and improvements | expand

Commit Message

André Apitzsch via B4 Relay Oct. 20, 2024, 10:13 p.m. UTC 
From: André Apitzsch <git@apitzsch.eu>

The driver defines IMX214_DEFAULT_LINK_FREQ 480000000, and then
IMX214_DEFAULT_PIXEL_RATE ((IMX214_DEFAULT_LINK_FREQ * 8LL) / 10),
which works out as 384MPix/s. (The 8 is 4 lanes and DDR.)

Parsing the PLL registers with the defined 24MHz input. We're in single
PLL mode, so MIPI frequency is directly linked to pixel rate.  VTCK ends
up being 1200MHz, and VTPXCK and OPPXCK both are 120MHz.  Section 5.3
"Frame rate calculation formula" says "Pixel rate
[pixels/s] = VTPXCK [MHz] * 4", so 120 * 4 = 480MPix/s, which basically
agrees with my number above.

3.1.4. MIPI global timing setting says "Output bitrate = OPPXCK * reg
0x113[7:0]", so 120MHz * 10, or 1200Mbit/s. That would be a link
frequency of 600MHz due to DDR.
That also matches to 480MPix/s * 10bpp / 4 lanes / 2 for DDR.

Signed-off-by: André Apitzsch <git@apitzsch.eu>
---
 drivers/media/i2c/imx214.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/drivers/media/i2c/imx214.c b/drivers/media/i2c/imx214.c
index 4962cfe7c83d62425aeccb46a400fa93146f14ea..5d411452d342fdb177619cd1c9fd9650d31089bb 100644
--- a/drivers/media/i2c/imx214.c
+++ b/drivers/media/i2c/imx214.c
@@ -24,7 +24,7 @@ 
 #define IMX214_MODE_STREAMING		0x01
 
 #define IMX214_DEFAULT_CLK_FREQ	24000000
-#define IMX214_DEFAULT_LINK_FREQ 480000000
+#define IMX214_DEFAULT_LINK_FREQ 600000000
 #define IMX214_DEFAULT_PIXEL_RATE ((IMX214_DEFAULT_LINK_FREQ * 8LL) / 10)
 #define IMX214_FPS 30
 #define IMX214_MBUS_CODE MEDIA_BUS_FMT_SRGGB10_1X10