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Message-ID: <CAPybu_3MEY8GziQFwA6QFfycdYvLovrY0bQOv=xSbOS=X+627A@mail.gmail.com>
Date: Tue, 11 Mar 2025 21:49:09 +0100
From: Ricardo Ribalda Delgado <ribalda@...nel.org>
To: git@...tzsch.eu
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>, ~postmarketos/upstreaming@...ts.sr.ht,
phone-devel@...r.kernel.org, linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 1/4] media: i2c: imx214: Calculate link bit rate
from clock frequency
On Sat, Mar 8, 2025 at 10:48 PM André Apitzsch via B4 Relay
<devnull+git.apitzsch.eu@...nel.org> wrote:
>
> From: André Apitzsch <git@...tzsch.eu>
>
> Replace the magic link bit rate number (4800) by its calculation based
> on the used parameters and the provided external clock frequency.
>
> The link bit rate is output bitrate multiplied by the number lanes. The
> output bitrate is the OPPXCK clock frequency multiplied by the number of
> bits per pixel. The OPPXCK clock frequency is OPCK multiplied by the
> OPPXCK clock division ratio. And OPCK is the external clock frequency
> multiplied by the PreDivider setting and the PLL multiple setting.
>
> Signed-off-by: André Apitzsch <git@...tzsch.eu>
Acked-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
> drivers/media/i2c/imx214.c | 51 +++++++++++++++++++++++++++++++++-------------
> 1 file changed, 37 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/media/i2c/imx214.c b/drivers/media/i2c/imx214.c
> index 6c3f6f3c8b1f7724110dc55fead0f8a168edf35b..14a4c5094799014da38ab1beec401f0d923c2152 100644
> --- a/drivers/media/i2c/imx214.c
> +++ b/drivers/media/i2c/imx214.c
> @@ -84,6 +84,7 @@
> #define IMX214_CSI_DATA_FORMAT_RAW10 0x0A0A
> #define IMX214_CSI_DATA_FORMAT_COMP6 0x0A06
> #define IMX214_CSI_DATA_FORMAT_COMP8 0x0A08
> +#define IMX214_BITS_PER_PIXEL_MASK 0xFF
>
> #define IMX214_REG_CSI_LANE_MODE CCI_REG8(0x0114)
> #define IMX214_CSI_2_LANE_MODE 1
> @@ -104,11 +105,23 @@
>
> /* PLL settings */
> #define IMX214_REG_VTPXCK_DIV CCI_REG8(0x0301)
> +#define IMX214_DEFAULT_VTPXCK_DIV 5
> +
> #define IMX214_REG_VTSYCK_DIV CCI_REG8(0x0303)
> +#define IMX214_DEFAULT_VTSYCK_DIV 2
> +
> #define IMX214_REG_PREPLLCK_VT_DIV CCI_REG8(0x0305)
> +#define IMX214_DEFAULT_PREPLLCK_VT_DIV 3
> +
> #define IMX214_REG_PLL_VT_MPY CCI_REG16(0x0306)
> +#define IMX214_DEFAULT_PLL_VT_MPY 150
> +
> #define IMX214_REG_OPPXCK_DIV CCI_REG8(0x0309)
> +#define IMX214_DEFAULT_OPPXCK_DIV 10
> +
> #define IMX214_REG_OPSYCK_DIV CCI_REG8(0x030b)
> +#define IMX214_DEFAULT_OPSYCK_DIV 1
> +
> #define IMX214_REG_PLL_MULT_DRIV CCI_REG8(0x0310)
> #define IMX214_PLL_SINGLE 0
> #define IMX214_PLL_DUAL 1
> @@ -204,6 +217,14 @@
> #define IMX214_PIXEL_ARRAY_WIDTH 4208U
> #define IMX214_PIXEL_ARRAY_HEIGHT 3120U
>
> +/* Link bit rate for a given input clock frequency in single PLL mode */
> +#define IMX214_LINK_BIT_RATE(clk_freq) \
> + (((clk_freq) / 1000000) / IMX214_DEFAULT_PREPLLCK_VT_DIV \
> + * IMX214_DEFAULT_PLL_VT_MPY \
> + / (IMX214_DEFAULT_OPSYCK_DIV * IMX214_DEFAULT_OPPXCK_DIV) \
> + * (IMX214_CSI_DATA_FORMAT_RAW10 & IMX214_BITS_PER_PIXEL_MASK) \
> + * (IMX214_CSI_4_LANE_MODE + 1))
I am always very scared of these macros.... Integer over/underflows
are very easy to miss
If we support a small number of frequencies I would rather see a
function with a switch and a comment explaining where the number comes
from.
> +
> static const char * const imx214_supply_name[] = {
> "vdda",
> "vddd",
> @@ -299,15 +320,16 @@ static const struct cci_reg_sequence mode_4096x2304[] = {
> { IMX214_REG_DIG_CROP_WIDTH, 4096 },
> { IMX214_REG_DIG_CROP_HEIGHT, 2304 },
>
> - { IMX214_REG_VTPXCK_DIV, 5 },
> - { IMX214_REG_VTSYCK_DIV, 2 },
> - { IMX214_REG_PREPLLCK_VT_DIV, 3 },
> - { IMX214_REG_PLL_VT_MPY, 150 },
> - { IMX214_REG_OPPXCK_DIV, 10 },
> - { IMX214_REG_OPSYCK_DIV, 1 },
> + { IMX214_REG_VTPXCK_DIV, IMX214_DEFAULT_VTPXCK_DIV },
> + { IMX214_REG_VTSYCK_DIV, IMX214_DEFAULT_VTSYCK_DIV },
> + { IMX214_REG_PREPLLCK_VT_DIV, IMX214_DEFAULT_PREPLLCK_VT_DIV },
> + { IMX214_REG_PLL_VT_MPY, IMX214_DEFAULT_PLL_VT_MPY },
> + { IMX214_REG_OPPXCK_DIV, IMX214_DEFAULT_OPPXCK_DIV },
> + { IMX214_REG_OPSYCK_DIV, IMX214_DEFAULT_OPSYCK_DIV },
> { IMX214_REG_PLL_MULT_DRIV, IMX214_PLL_SINGLE },
>
> - { IMX214_REG_REQ_LINK_BIT_RATE, IMX214_LINK_BIT_RATE_MBPS(4800) },
> + { IMX214_REG_REQ_LINK_BIT_RATE,
> + IMX214_LINK_BIT_RATE_MBPS(IMX214_LINK_BIT_RATE(IMX214_DEFAULT_CLK_FREQ)) },
>
> { CCI_REG8(0x3A03), 0x09 },
> { CCI_REG8(0x3A04), 0x50 },
> @@ -362,15 +384,16 @@ static const struct cci_reg_sequence mode_1920x1080[] = {
> { IMX214_REG_DIG_CROP_WIDTH, 1920 },
> { IMX214_REG_DIG_CROP_HEIGHT, 1080 },
>
> - { IMX214_REG_VTPXCK_DIV, 5 },
> - { IMX214_REG_VTSYCK_DIV, 2 },
> - { IMX214_REG_PREPLLCK_VT_DIV, 3 },
> - { IMX214_REG_PLL_VT_MPY, 150 },
> - { IMX214_REG_OPPXCK_DIV, 10 },
> - { IMX214_REG_OPSYCK_DIV, 1 },
> + { IMX214_REG_VTPXCK_DIV, IMX214_DEFAULT_VTPXCK_DIV },
> + { IMX214_REG_VTSYCK_DIV, IMX214_DEFAULT_VTSYCK_DIV },
> + { IMX214_REG_PREPLLCK_VT_DIV, IMX214_DEFAULT_PREPLLCK_VT_DIV },
> + { IMX214_REG_PLL_VT_MPY, IMX214_DEFAULT_PLL_VT_MPY },
> + { IMX214_REG_OPPXCK_DIV, IMX214_DEFAULT_OPPXCK_DIV },
> + { IMX214_REG_OPSYCK_DIV, IMX214_DEFAULT_OPSYCK_DIV },
> { IMX214_REG_PLL_MULT_DRIV, IMX214_PLL_SINGLE },
>
> - { IMX214_REG_REQ_LINK_BIT_RATE, IMX214_LINK_BIT_RATE_MBPS(4800) },
> + { IMX214_REG_REQ_LINK_BIT_RATE,
> + IMX214_LINK_BIT_RATE_MBPS(IMX214_LINK_BIT_RATE(IMX214_DEFAULT_CLK_FREQ)) },
>
> { CCI_REG8(0x3A03), 0x04 },
> { CCI_REG8(0x3A04), 0xF8 },
>
> --
> 2.48.1
>
>
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