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Fix ticking noise on PP5002 introduced with tthe transfer optimisation in r17097.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17158 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Jens Arnold 2008-04-18 18:52:11 +00:00
parent 3dcb4ff97f
commit a73b13cfff
1 changed files with 15 additions and 13 deletions
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28
firmware/target/arm/pcm-pp.c
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@ -107,17 +107,18 @@ void pcm_apply_settings(void)
pcm_curr_sampr = pcm_freq;
}
/* ASM optimised FIQ handler. Checks for the minimum allowed loop cycles by evalutation of
* free IISFIFO-slots against available source buffer words. Through this it is possible to
* move the check for IIS_TX_FREE_COUNT outside the loop and do some further optimization.
* Right after the loops (source buffer -> IISFIFO) are done we need to check whether we
* have to exit FIQ handler (this must be done, if all free FIFO slots were filled) or
* we will have to get some new source data.
* Important information kept from former ASM implementation (not used anymore): GCC fails
* to make use of the fact that FIQ mode has registers r8-r14 banked, and so does not need
* to be saved. This routine uses only these registers, and so will never touch the stack
* unless it actually needs to do so when calling pcm_callback_for_more. C version is still
* included below for reference and testing.
/* ASM optimised FIQ handler. Checks for the minimum allowed loop cycles by
* evalutation of free IISFIFO-slots against available source buffer words.
* Through this it is possible to move the check for IIS_TX_FREE_COUNT outside
* the loop and do some further optimization. Right after the loops (source
* buffer -> IISFIFO) are done we need to check whether we have to exit FIQ
* handler (this must be done, if all free FIFO slots were filled) or we will
* have to get some new source data. Important information kept from former
* ASM implementation (not used anymore): GCC fails to make use of the fact
* that FIQ mode has registers r8-r14 banked, and so does not need to be saved.
* This routine uses only these registers, and so will never touch the stack
* unless it actually needs to do so when calling pcm_callback_for_more.
* C version is still included below for reference and testing.
*/
#if 1
void fiq_playback(void) ICODE_ATTR __attribute__((naked));
@ -169,8 +170,9 @@ void fiq_playback(void)
".check_fifo: \n"
"ldr r0, [r10, %[cfg]] \n" /* read IISFIFO_CFG to check FIFO status */
"and r0, r0, %[mask] \n" /* r0 = IIS_TX_FREE_COUNT << 23 (PP5002) */
"mov r1, r0, lsr #24 \n" /* number of free pairs of FIFO slots */
"movs r1, r0, lsr #24 \n" /* number of free pairs of FIFO slots */
"beq .exit \n" /* no complete pair? -> exit */
"cmp r1, r9, lsr #2 \n" /* number of words from source */
"movgt r1, r9, lsr #2 \n" /* r1 = amount of allowed loops */
"sub r9, r9, r1, lsl #2 \n" /* r1 words will be written in following loop */