Re: [PATCH] mediatek: dsi: Add dsi per-frame lp code for mt8188

From: CK Hu (胡俊光)
Date: Wed Mar 20 2024 - 02:03:58 EST

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Hi, Shuijing:

Add 'drm/' in the title.

On Thu, 2024-03-14 at 17:41 +0800, Shuijing Li wrote:
> Adding the per-frame lp function of mt8188, which can keep HFP in HS
> and
> reduce the time required for each line to enter and exit low power.
> Per Frame LP:
> |<----------One Active Frame-------->|
> --______________________________________----___________________
> ^HSA+HBP^^RGB^^HFP^^HSA+HBP^^RGB^^HFP^ ^HSA+HBP^^RGB^^HFP^
>
> Per Line LP:
> |<---------------One Active Frame----------->|
> --______________--______________--______________----______________
> ^HSA+HBP^^RGB^ ^HSA+HBP^^RGB^ ^HSA+HBP^^RGB^ ^HSA+HBP^^RGB^

As I know, some low power mode would has some side effect. For example,
CPU dvfs would let CPU run in low frequency when CPU is idle, but when
CPU is suddenly busy, it would take some time to let CPU frequency
speed up and may cause some real time issue. Does this have any side
effect. If so, please describe it.

>
> Signed-off-by: Shuijing Li <shuijing.li@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/mediatek/mtk_dsi.c | 100
> +++++++++++++++++++++++++++++
> 1 file changed, 100 insertions(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index a2fdfc8ddb15..e6f4807c8711 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -83,6 +83,7 @@
> #define DSI_HSA_WC 0x50
> #define DSI_HBP_WC 0x54
> #define DSI_HFP_WC 0x58
> +#define DSI_BLLP_WC 0x5C
>
> #define DSI_CMDQ_SIZE 0x60
> #define CMDQ_SIZE 0x3f
> @@ -180,6 +181,7 @@ struct mtk_dsi_driver_data {
> bool has_shadow_ctl;
> bool has_size_ctl;
> bool cmdq_long_packet_ctl;
> + bool support_per_frame_lp;
> };
>
> struct mtk_dsi {
> @@ -516,6 +518,103 @@ static void mtk_dsi_config_vdo_timing(struct
> mtk_dsi *dsi)
> (vm->hactive * dsi_tmp_buf_bpp + 2) % dsi-
> >lanes;
> }
>
> + if (dsi->driver_data->support_per_frame_lp) {
> + unsigned int lpx = 0, da_hs_exit = 0, da_hs_prep = 0,
> da_hs_trail = 0;
> + unsigned int da_hs_zero = 0, ps_wc = 0, hs_vb_ps_wc =
> 0;

It's not necessary to initialize to zero because these variable would
be assigned to other value later.

> + u32 bllp_wc, bllp_en, v_active_roundup, hstx_cklp_wc;
> + u32 hstx_cklp_wc_max, hstx_cklp_wc_min;
> +
> + da_hs_trail = (readl(dsi->regs + DSI_PHY_TIMECON0) >>
> 24) & 0xff;

operator '>>' has higher priority than operator '&', so it's not
necessary to add '()'.

> + bllp_en = (readl(dsi->regs + DSI_TXRX_CTRL) >> 7) &
> 0x1;
> + if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE) {
> + horizontal_sync_active_byte =
> + (vm->hsync_len * dsi_tmp_buf_bpp - 10);

'()' is redundant.

> + horizontal_backporch_byte =
> + (vm->hback_porch * dsi_tmp_buf_bpp -
> 10);

ditto.

> + horizontal_frontporch_byte =
> + (vm->hfront_porch * dsi_tmp_buf_bpp -
> 12);

ditto.

> +
> + ps_wc = readl(dsi->regs + DSI_PSCTRL) & 0x7fff;
> + v_active_roundup = (32 +
> horizontal_sync_active_byte +
> + horizontal_backporch_byte + ps_wc +
> + horizontal_frontporch_byte) % dsi-
> >lanes;
> + if (v_active_roundup)
> + horizontal_backporch_byte =
> horizontal_backporch_byte +
> + dsi->lanes - v_active_roundup;
> + hstx_cklp_wc_min = (DIV_ROUND_UP((12 + 2 + 4 +
> + horizontal_sync_active_byte), dsi-
> >lanes) + da_hs_trail + 1)
> + * dsi->lanes / 6 - 1;
> + hstx_cklp_wc_max = (DIV_ROUND_UP((20 + 6 + 4 +
> + horizontal_sync_active_byte +
> horizontal_backporch_byte +
> + ps_wc), dsi->lanes) + da_hs_trail + 1)
> * dsi->lanes / 6 - 1;
> + } else {
> + horizontal_sync_active_byte = vm->hsync_len *
> dsi_tmp_buf_bpp - 4;
> +
> + horizontal_backporch_byte = (vm->hback_porch +
> vm->hsync_len) *
> + dsi_tmp_buf_bpp - 10;
> + hstx_cklp_wc_min = (DIV_ROUND_UP(4, dsi->lanes)
> + da_hs_trail + 1)
> + * dsi->lanes / 6 - 1;
> +
> + if (dsi->mode_flags &
> MIPI_DSI_MODE_VIDEO_BURST) {
> + ps_wc = readl(dsi->regs + DSI_PSCTRL) &
> 0x7fff;
> + bllp_wc = readl(dsi->regs +
> DSI_BLLP_WC) & 0xfff;
> + horizontal_frontporch_byte = (vm-
> >hfront_porch *
> + dsi_tmp_buf_bpp - 18);
> +
> + v_active_roundup = (28 +
> horizontal_backporch_byte + ps_wc +
> + horizontal_frontporch_byte +
> bllp_wc) % dsi->lanes;
> + if (v_active_roundup)
> + horizontal_backporch_byte =
> horizontal_backporch_byte +
> + dsi->lanes - v_active_roundup;
> + if (bllp_en) {
> + hstx_cklp_wc_max =
> (DIV_ROUND_UP((16 + 6 + 4 +
> + horizontal_backporch_by
> te + bllp_wc + ps_wc),
> + dsi->lanes) +
> da_hs_trail + 1) * dsi->lanes / 6 - 1;
> + } else {
> + hstx_cklp_wc_max =
> (DIV_ROUND_UP((12 + 4 + 4 +
> + horizontal_backporch_by
> te + bllp_wc + ps_wc),
> + dsi->lanes) +
> da_hs_trail + 1) * dsi->lanes / 6 - 1;
> + }
> + } else {
> + ps_wc = readl(dsi->regs + DSI_PSCTRL) &
> 0x7fff;
> + horizontal_frontporch_byte = (vm-
> >hfront_porch *
> + dsi_tmp_buf_bpp - 12);
> +
> + v_active_roundup = (22 +
> horizontal_backporch_byte + ps_wc +
> + horizontal_frontporch_byte) %
> dsi->lanes;
> + if (v_active_roundup)
> + horizontal_backporch_byte =
> horizontal_backporch_byte +
> + dsi->lanes - v_active_roundup;
> +
> + hstx_cklp_wc_max = (DIV_ROUND_UP((12 +
> 4 + 4 +
> + horizontal_backporch_byte +
> ps_wc),
> + dsi->lanes) + da_hs_trail + 1)
> * dsi->lanes / 6 - 1;
> + }
> + }
> + hstx_cklp_wc = (readl(dsi->regs + DSI_HSTX_CKL_WC) >>
> 2) & 0x3fff;

Hardware register is set according to software variable, so you could
get this value from software variable. DSI_HSTX_CKL_WC is set in
mtk_dsi_ps_control_vact() as ps_wc, so you could use ps_wc instead of
read it back from register.

Regards,
CK

> + if (hstx_cklp_wc <= hstx_cklp_wc_min ||
> + hstx_cklp_wc >= hstx_cklp_wc_max) {
> + hstx_cklp_wc = (hstx_cklp_wc_max / 2) << 2;
> + writel(hstx_cklp_wc, dsi->regs +
> DSI_HSTX_CKL_WC);
> + }
> + hstx_cklp_wc = hstx_cklp_wc >> 2;
> + if (hstx_cklp_wc <= hstx_cklp_wc_min ||
> + hstx_cklp_wc >= hstx_cklp_wc_max) {
> + DRM_WARN("Wrong setting of hstx_ckl_wc\n");
> + }
> +
> + lpx = readl(dsi->regs + DSI_PHY_TIMECON0) & 0xff;
> + da_hs_exit = (readl(dsi->regs + DSI_PHY_TIMECON1) >>
> 24) & 0xff;
> + da_hs_prep = (readl(dsi->regs + DSI_PHY_TIMECON0) >> 8)
> & 0xff;
> + da_hs_zero = (readl(dsi->regs + DSI_PHY_TIMECON0) >>
> 16) & 0xff;
> + ps_wc = readl(dsi->regs + DSI_PSCTRL) & 0x7fff;
> + hs_vb_ps_wc = ps_wc -
> + (lpx + da_hs_exit + da_hs_prep + da_hs_zero +
> 2)
> + * dsi->lanes;
> + horizontal_frontporch_byte = (1 << 31)
> + | (hs_vb_ps_wc << 16)
> + | (horizontal_frontporch_byte);
> + }
> writel(horizontal_sync_active_byte, dsi->regs + DSI_HSA_WC);
> writel(horizontal_backporch_byte, dsi->regs + DSI_HBP_WC);
> writel(horizontal_frontporch_byte, dsi->regs + DSI_HFP_WC);
> @@ -1246,6 +1345,7 @@ static const struct mtk_dsi_driver_data
> mt8188_dsi_driver_data = {
> .has_shadow_ctl = true,
> .has_size_ctl = true,
> .cmdq_long_packet_ctl = true,
> + .support_per_frame_lp = true,
> };
>
> static const struct of_device_id mtk_dsi_of_match[] = {

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