[Freedreno] [PATCH v4 1/6] drm/msm: Add MSM-specific DSC helper methods
Dmitry Baryshkov
dmitry.baryshkov at linaro.org
Wed Apr 5 23:37:08 UTC 2023
On 06/04/2023 02:34, Abhinav Kumar wrote:
>
>
> On 4/5/2023 12:26 PM, Dmitry Baryshkov wrote:
>> On 05/04/2023 03:41, 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.
>>>
>>> Changes in v4:
>>> - Changed msm_dsc_get_uncompressed_pclk_per_intf to
>>> msm_dsc_get_pclk_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..0539221eb09d
>>> --- /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);
>>
>> If we remove 3 * dsc->bits_per_components from both numerator and
>> denominator, this whole function seems to be as simple as
>> DIV_ROUND_UP(dsc->slice_width * bpp, 8)
>>
>> Or, if you prefer FP math, drm_fixp_from_fraction(dsc->slice_width *
>> bpp, 8).
>>
>
> True and thats not really surprising because bytes_per_soft_slice is
> eventually (dsc->slice_width * bpp, 8)
>
> I also thought about it after you mentioned that they will cancel out
> then why was downstream code and our programming guide doing this way.
>
> So i thought a bit more and the reason from what I can see is that its
> showing that compression ratio was factored into the math while
> calculating it. If we just go with (dsc->slice_width * bpp, 8), it does
> not really show that this was actually compressed bytes per slice
> leading to the earlier confusion that it was uncompressed pclk while it
> actually was.
I'd say, name we can name that dsc_bpp or compressed_bpp instead of just
bpp, this way showing that it is a compressed pclk. But please don't
complicate the math.
>
>>> +}
>>> +
>>> +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_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));
>>
>> And this is then DIV_ROUND_UP(dsc->slice_width * dsc->slice_count *
>> bpp, 8)
>>
>>> +
>>> + return drm_fixp2int_ceil(data_width);
>>> +}
>>> 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..31116a31090f
>>> --- /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_pclk_per_intf - Calculate pclk per interface.
>>> + * @dsc: Pointer to drm dsc config struct
>>> + *
>>> + * Note: This value will then be passed along to DSI and DP for some
>>> more
>>> + * calculations. This is because DSI and DP divide the pclk_per_intf
>>> value
>>> + * by different values depending on if widebus is enabled.
>>> + */
>>> +int msm_dsc_get_pclk_per_intf(struct drm_dsc_config *dsc);
>>
>> empty line, please
>>
>>> +#endif /* MSM_DSC_HELPER_H_ */
>>>
>>
--
With best wishes
Dmitry
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