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triangle_ta: reorder SH4 store queue comment

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This commit is contained in:
Zack Buhman 2025-08-20 21:56:15 -05:00
parent da0f4435b1
commit 3fc18fa1b7
1 changed files with 32 additions and 33 deletions
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65
triangle_ta.c
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@ -255,6 +255,37 @@ void transfer_isp_tsp_background_parameter(uint32_t isp_tsp_parameter_start)
#define ISP_BACKGND_T__TAG_ADDRESS(n) (((n) & 0x1fffff) << 3)
#define ISP_BACKGND_T__TAG_OFFSET(n) (((n) & 0x7) << 0)
/******************************************************************************
SH4 store queue
******************************************************************************/
/*
The TA polygon converter FIFO requires 32-byte bus access. Attempts to access
the TA with smaller bus accesses will result in incorrect TA operation. The
Dreamcast has three mechanisms that can generate 32-byte writes:
- SH4 store queue (commonly used)
- Holly CH2-DMA (commonly used)
- meticulous and clever use of SH4 cache writeback (esoteric forbidden technique)
Of these, the mechanism that requires the least code is the SH4 store queue,
so this demo will also use the SH4 store queue for that reason.
The SH4 store queue is described in sh7091pm_e.pdf printed page 61-64 and
79-81.
*/
// sh7091pm_e.pdf:
// > Issuing a PREF instruction for P4 area H'E000 0000 to H'E3FF FFFC starts a
// > burst transfer from the SQs to external memory.
#define pref(address) \
{ asm volatile ("pref @%0" : : "r" (address) : "memory"); }
volatile uint32_t * SH7091__CCN__QACR0 = (volatile uint32_t *)(0xff000000 + 0x38);
volatile uint32_t * SH7091__CCN__QACR1 = (volatile uint32_t *)(0xff000000 + 0x3c);
/******************************************************************************
TA Parameters
******************************************************************************/
@ -330,17 +361,6 @@ typedef struct ta_vertex_parameter__polygon_type_0 {
} ta_vertex_parameter__polygon_type_0;
static_assert((sizeof (struct ta_vertex_parameter__polygon_type_0)) == 32);
/*
sh7091pm_e.pdf:
> Issuing a PREF instruction for P4 area H'E000 0000 to H'E3FF FFFC starts a burst transfer from
> the SQs to external memory.
*/
#define pref(address) \
{ asm volatile ("pref @%0" : : "r" (address) : "memory"); }
volatile uint32_t * SH7091__CCN__QACR0 = (volatile uint32_t *)(0xff000000 + 0x38);
volatile uint32_t * SH7091__CCN__QACR1 = (volatile uint32_t *)(0xff000000 + 0x3c);
#define PARAMETER_CONTROL_WORD__PARA_CONTROL__PARA_TYPE__END_OF_LIST (0 << 29)
#define PARAMETER_CONTROL_WORD__PARA_CONTROL__PARA_TYPE__POLYGON_OR_MODIFIER_VOLUME (4 << 29)
#define PARAMETER_CONTROL_WORD__PARA_CONTROL__PARA_TYPE__VERTEX_PARAMETER (7 << 29)
@ -348,6 +368,7 @@ volatile uint32_t * SH7091__CCN__QACR1 = (volatile uint32_t *)(0xff000000 + 0x3c
#define PARAMETER_CONTROL_WORD__PARA_CONTROL__LIST_TYPE__OPAQUE (0 << 24)
#define PARAMETER_CONTROL_WORD__OBJ_CONTROL__COL_TYPE__PACKED_COLOR (0 << 4)
#define PARAMETER_CONTROL_WORD__OBJ_CONTROL__GOURAUD (1 << 1)
void transfer_ta_triangle()
{
// set the store queue destination address to the TA Polygon Converter FIFO
@ -459,28 +480,6 @@ void transfer_ta_triangle()
store_queue_ix += (sizeof (ta_global_parameter__end_of_list));
}
/******************************************************************************
SH4 store queue
******************************************************************************/
/*
The TA polygon converter FIFO requires 32-byte bus access. Attempts to access
the TA with smaller bus accesses will result in incorrect TA operation. The
Dreamcast has three mechanisms that can generate 32-byte writes:
- SH4 store queue (commonly used)
- Holly CH2-DMA (commonly used)
- meticulous and clever use of SH4 cache writeback (esoteric forbidden technique)
Of these, the mechanism that requires the least code is the SH4 store queue,
so this demo will also use the SH4 store queue for that reason.
The SH4 store queue is described in sh7091pm_e.pdf printed page 61-64 and
79-81.
*/
/******************************************************************************
Holly register definitions
******************************************************************************/