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Date: Wed, 12 Jun 2024 01:35:15 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: Shawn Sung (宋孝謙) <Shawn.Sung@...iatek.com>,
"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC: "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Bibby Hsieh (謝濟遠) <Bibby.Hsieh@...iatek.com>,
"jason-ch.chen@...iatek.corp-partner.google.com"
<jason-ch.chen@...iatek.corp-partner.google.com>,
Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
"daniel@...ll.ch" <daniel@...ll.ch>, "p.zabel@...gutronix.de"
<p.zabel@...gutronix.de>, "dri-devel@...ts.freedesktop.org"
<dri-devel@...ts.freedesktop.org>, "airlied@...il.com" <airlied@...il.com>,
"sean@...rly.run" <sean@...rly.run>, "matthias.bgg@...il.com"
<matthias.bgg@...il.com>, "fshao@...omium.org" <fshao@...omium.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"angelogioacchino.delregno@...labora.com"
<angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v8 15/16] drm/mediatek: Support CRC in OVL
Hi, Shawn:
On Thu, 2024-06-06 at 17:26 +0800, Shawn Sung wrote:
> From: Hsiao Chien Sung <shawn.sung@...iatek.com>
>
> We choose OVL as the CRC generator from other hardware
> components that are also capable of calculating CRCs,
> since its frame done event triggers vblanks, it can be
> used as a signal to know when is safe to retrieve CRC of
> the frame.
>
> Please note that position of the hardware component
> that is chosen as CRC generator in the display path is
> significant. For example, while OVL is the first module
> in VDOSYS0, its CRC won't be affected by the modules
> after it, which means effects applied by PQ, Gamma,
> Dither or any other components after OVL won't be
> calculated in CRC generation.
>
> Signed-off-by: Hsiao Chien Sung <shawn.sung@...iatek.com>
> ---
[snip]
>
> void mtk_ovl_stop(struct device *dev)
> @@ -489,6 +579,83 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
> (state->base.fb && !state->base.fb->format->has_alpha))
> ignore_pixel_alpha = OVL_CONST_BLEND;
>
> + /*
> + * OVL only supports 8 bits data in CRC calculation, transform 10-bit
> + * RGB to 8-bit RGB by leveraging the ability of the Y2R (YUV-to-RGB)
> + * hardware to multiply coefficients, although there is nothing to do
> + * with the YUV format.
> + */
> + if (ovl->data->supports_clrfmt_ext) {
> + u32 y2r_coef = 0, y2r_offset = 0, r2r_coef = 0, csc_en = 0;
> +
> + if (is_10bit_rgb(fmt)) {
> + con |= OVL_CON_MTX_AUTO_DIS | OVL_CON_MTX_EN | OVL_CON_MTX_PROGRAMMABLE;
> +
> + /*
> + * Y2R coefficient setting
> + * bit 13 is 2^1, bit 12 is 2^0, bit 11 is 2^-1,
> + * bit 10 is 2^-2 = 0.25
> + */
> + y2r_coef = BIT(10);
> +
> + /* -1 in 10bit */
> + y2r_offset = GENMASK(10, 0) - 1;
I don't know why do this? If an input value is 0x100, then
0x100 right shit 2 bit become 0x40.
0x40 - 1 = 0x3f.
0x3f left shift 2 bit become 0xfc.
So input 0x100 and output 0xfc. Why?
> +
> + /*
> + * R2R coefficient setting
> + * bit 19 is 2^1, bit 18 is 2^0, bit 17 is 2^-1,
> + * bit 20 is 2^2 = 4
> + */
> + r2r_coef = BIT(20);
> +
> + /* CSC_EN is for R2R */
> + csc_en = OVL_CLRFMT_EXT1_CSC_EN(idx);
> +
> + /*
> + * 1. YUV input data - 1 and shift right for 2 bits to remove it
> + * [R'] [0.25 0 0] [Y in - 1]
> + * [G'] = [ 0 0.25 0] * [U in - 1]
> + * [B'] [ 0 0 0.25] [V in - 1]
> + *
> + * 2. shift left for 2 bit letting the last 2 bits become 0
You truncate the last two bit, so some quality lost. I think the
quality is main function and CRC is just for debug. So it's better that
in normal case we keep quality and only for debug to lost the quality.
I have another question. You just truncate the last two bit but it is
still 10 bit value, so CRC could calculate this 10 bit value? I don't
know why you say CRC just for 8 bit?
Regards,
CK
> + * [R out] [ 4 0 0] [R']
> + * [G out] = [ 0 4 0] * [G']
> + * [B out] [ 0 0 4] [B']
> + */
> + }
> +
> + mtk_ddp_write_mask(cmdq_pkt, y2r_coef,
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_Y2R_PARA_R0(idx),
> + OVL_Y2R_PARA_C_CF_RMY);
> + mtk_ddp_write_mask(cmdq_pkt, (y2r_coef << 16),
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_Y2R_PARA_G0(idx),
> + OVL_Y2R_PARA_C_CF_GMU);
> + mtk_ddp_write_mask(cmdq_pkt, y2r_coef,
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_Y2R_PARA_B1(idx),
> + OVL_Y2R_PARA_C_CF_BMV);
> +
> + mtk_ddp_write_mask(cmdq_pkt, y2r_offset,
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_Y2R_PARA_YUV_A_0(idx),
> + OVL_Y2R_PARA_C_CF_YA);
> + mtk_ddp_write_mask(cmdq_pkt, (y2r_offset << 16),
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_Y2R_PARA_YUV_A_0(idx),
> + OVL_Y2R_PARA_C_CF_UA);
> + mtk_ddp_write_mask(cmdq_pkt, y2r_offset,
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_Y2R_PARA_YUV_A_1(idx),
> + OVL_Y2R_PARA_C_CF_VA);
> +
> + mtk_ddp_write_relaxed(cmdq_pkt, r2r_coef,
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_R2R_R0(idx));
> + mtk_ddp_write_relaxed(cmdq_pkt, r2r_coef,
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_R2R_G1(idx));
> + mtk_ddp_write_relaxed(cmdq_pkt, r2r_coef,
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_R2R_B2(idx));
> +
> + mtk_ddp_write_mask(cmdq_pkt, csc_en,
> + &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_CLRFMT_EXT1,
> + OVL_CLRFMT_EXT1_CSC_EN(idx));
> + }
> +
> if (pending->rotation & DRM_MODE_REFLECT_Y) {
> con |= OVL_CON_VIRT_FLIP;
> addr += (pending->height - 1) * pending->pitch;
>
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