[PATCH v3 1/6] drm/msm: Add MSM-specific DSC helper methods

[Abhinav Kumar]

On 4/4/2023 4:56 PM, Jessica Zhang wrote:
> Introduce MSM-specific DSC helper methods, as some calculations are
> common between DP and DSC.
> 
> Changes in v2:
> - Moved files up to msm/ directory
> - Dropped get_comp_ratio() helper
> - Used drm_int2fixp() to convert to integers to fp
> - Style changes to improve readability
> - Dropped unused bpp variable in msm_dsc_get_dce_bytes_per_line()
> - Changed msm_dsc_get_slice_per_intf() to a static inline method
> - Dropped last division step of msm_dsc_get_pclk_per_line() and changed
>    method name accordingly
> - Changed DSC_BPP macro to drm_dsc_get_bpp_int() helper method
> - Fixed some math issues caused by passing in incorrect types to
>    drm_fixed methods in get_bytes_per_soft_slice()
> 
> Changes in v3:
> - Dropped src_bpp parameter from all methods -- src_bpp can be
>    calculated as dsc->bits_per_component * 3
> - Dropped intf_width parameter from get_bytes_per_soft_slice()
> - Moved dsc->bits_per_component to numerator calculation in
>    get_bytes_per_soft_slice()
> - Renamed msm_dsc_get_uncompressed_pclk_per_line to
>    *_get_uncompressed_pclk_per_intf()
> - Removed dsc->slice_width check from
>    msm_dsc_get_uncompressed_pclk_per_intf()
> - Made get_bytes_per_soft_slice() a public method (this will be called
>    later to help calculate DP pclk params)
> - Added documentation in comments
> - Moved extra_eol_bytes math out of msm_dsc_get_eol_byte_num() and
>    renamed msm_dsc_get_eol_byte_num to *_get_bytes_per_intf.
> 
> Signed-off-by: Jessica Zhang <quic_jesszhan at quicinc.com>
> ---
>   drivers/gpu/drm/msm/Makefile         |  1 +
>   drivers/gpu/drm/msm/msm_dsc_helper.c | 47 ++++++++++++++++++++++++
>   drivers/gpu/drm/msm/msm_dsc_helper.h | 70 ++++++++++++++++++++++++++++++++++++
>   3 files changed, 118 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/Makefile b/drivers/gpu/drm/msm/Makefile
> index 7274c41228ed..b814fc80e2d5 100644
> --- a/drivers/gpu/drm/msm/Makefile
> +++ b/drivers/gpu/drm/msm/Makefile
> @@ -94,6 +94,7 @@ msm-y += \
>   	msm_atomic_tracepoints.o \
>   	msm_debugfs.o \
>   	msm_drv.o \
> +	msm_dsc_helper.o \
>   	msm_fb.o \
>   	msm_fence.o \
>   	msm_gem.o \
> diff --git a/drivers/gpu/drm/msm/msm_dsc_helper.c b/drivers/gpu/drm/msm/msm_dsc_helper.c
> new file mode 100644
> index 000000000000..c8c530211f50
> --- /dev/null
> +++ b/drivers/gpu/drm/msm/msm_dsc_helper.c
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <drm/drm_fixed.h>
> +
> +#include "msm_drv.h"
> +#include "msm_dsc_helper.h"
> +
> +s64 get_bytes_per_soft_slice(struct drm_dsc_config *dsc)
> +{
> +	int bpp = msm_dsc_get_bpp_int(dsc);
> +	s64 numerator_fp, denominator_fp;
> +	s64 comp_ratio_fp = drm_fixp_from_fraction(dsc->bits_per_component * 3, bpp);
> +
> +	numerator_fp = drm_int2fixp(dsc->slice_width * 3 * dsc->bits_per_component);
> +	denominator_fp = drm_fixp_mul(comp_ratio_fp, drm_int2fixp(8));
> +
> +	return drm_fixp_div(numerator_fp, denominator_fp);
> +}
> +
> +u32 msm_dsc_get_bytes_per_intf(struct drm_dsc_config *dsc, int intf_width)
> +{
> +	u32 bytes_per_soft_slice, bytes_per_intf;
> +	s64 bytes_per_soft_slice_fp;
> +	int slice_per_intf = msm_dsc_get_slice_per_intf(dsc, intf_width);
> +
> +	bytes_per_soft_slice_fp = get_bytes_per_soft_slice(dsc);
> +	bytes_per_soft_slice = drm_fixp2int_ceil(bytes_per_soft_slice_fp);
> +
> +	bytes_per_intf = bytes_per_soft_slice * slice_per_intf;
> +
> +	return bytes_per_intf;
> +}
> +
> +int msm_dsc_get_uncompressed_pclk_per_intf(struct drm_dsc_config *dsc)
> +{
> +	s64 data_width;
> +
> +	data_width = drm_fixp_mul(drm_int2fixp(dsc->slice_count),
> +			get_bytes_per_soft_slice(dsc));
> +
> +	return drm_fixp2int_ceil(data_width);
> +}

This is not really uncompressed pclk_per_intf. This is still calculated 
using the compression ratio so it is still compressed.

I would suggest changing this to msm_dsc_get_pclk_per_intf().

Lets keep it simple.

> diff --git a/drivers/gpu/drm/msm/msm_dsc_helper.h b/drivers/gpu/drm/msm/msm_dsc_helper.h
> new file mode 100644
> index 000000000000..5ee972eb247c
> --- /dev/null
> +++ b/drivers/gpu/drm/msm/msm_dsc_helper.h
> @@ -0,0 +1,70 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved
> + */
> +
> +#ifndef MSM_DSC_HELPER_H_
> +#define MSM_DSC_HELPER_H_
> +
> +#include <drm/display/drm_dsc_helper.h>
> +#include <drm/drm_modes.h>
> +
> +/*
> + * Helper methods for MSM specific DSC calculations that are common between timing engine,
> + * DSI, and DP.
> + */
> +
> +/**
> + * msm_dsc_get_bpp_int - get bits per pixel integer value
> + * @dsc: Pointer to drm dsc config struct
> + */
> +static inline int msm_dsc_get_bpp_int(struct drm_dsc_config *dsc)
> +{
> +	WARN_ON_ONCE(dsc->bits_per_pixel & 0xf);
> +	return dsc->bits_per_pixel >> 4;
> +}
> +
> +/**
> + * msm_dsc_get_slice_per_intf - get number of slices per interface
> + * @dsc: Pointer to drm dsc config struct
> + * @intf_width: interface width
> + */
> +static inline int msm_dsc_get_slice_per_intf(struct drm_dsc_config *dsc, int intf_width)
> +{
> +	return DIV_ROUND_UP(intf_width, dsc->slice_width);
> +}
> +
> +/**
> + * msm_dsc_get_dce_bytes_per_line - get bytes per line to help calculate data width
> + *	when configuring the timing engine
> + * @dsc: Pointer to drm dsc config struct
> + * @intf_width: interface width
> + */
> +static inline u32 msm_dsc_get_dce_bytes_per_line(struct drm_dsc_config *dsc, int intf_width)
> +{
> +	return DIV_ROUND_UP(msm_dsc_get_bpp_int(dsc) * intf_width, 8);
> +}
> +
> +/**
> + * get_bytes_per_soft_slice - get size of each soft slice for dsc
> + * @dsc: Pointer to drm dsc config struct
> + */
> +s64 get_bytes_per_soft_slice(struct drm_dsc_config *dsc);
> +
> +/**
> + * msm_dsc_get_bytes_per_intf - get total bytes per interface
> + * @dsc: Pointer to drm dsc config struct
> + * @intf_width: interface width
> + */
> +u32 msm_dsc_get_bytes_per_intf(struct drm_dsc_config *dsc, int intf_width);
> +
> +/**
> + * msm_dsc_get_uncompressed_pclk_per_intf - Calculate uncompressed pclk per line.
> + * @dsc: Pointer to drm dsc config struct
> + *
> + * Note: This value will then be passed along to DSI and DP to calculate pclk_per_intf.
> + * This is because DSI and DP divide the uncompressed pclk_per_intf by different
> + * values depending on if widebus is enabled.
> + */
> +int msm_dsc_get_uncompressed_pclk_per_intf(struct drm_dsc_config *dsc);
> +#endif /* MSM_DSC_HELPER_H_ */
>