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Re: [Qemu-devel] PL181 write problem
From: |
Hans-Erik Floryd |
Subject: |
Re: [Qemu-devel] PL181 write problem |
Date: |
Mon, 02 Feb 2009 16:36:56 +0100 |
User-agent: |
Thunderbird 2.0.0.19 (Windows/20081209) |
The following patch fixes this by writing all four bytes before checking
fifo_len.
I think your analysis is probably correct, but I'm not so keen on your
solution. You've got redundant loops/conditions.
It seemed like a good idea to not modify the read path since it works,
but it does make the code a bit complicated. In the following patch I've
broken read and write into separate loops which hopefully makes the code
easier to follow. s->datacnt needs to be checked for every byte written
or read since it might not be a multiple of 4.
Index: hw/pl181.c
===================================================================
--- hw/pl181.c (revision 5648)
+++ hw/pl181.c (working copy)
@@ -184,38 +184,28 @@
uint32_t bits;
uint32_t value;
int n;
- int limit;
int is_read;
is_read = (s->datactrl & PL181_DATA_DIRECTION) != 0;
if (s->datacnt != 0 && (!is_read || sd_data_ready(s->card))
&& !s->linux_hack) {
- limit = is_read ? PL181_FIFO_LEN : 0;
- n = 0;
- value = 0;
- while (s->datacnt && s->fifo_len != limit) {
- if (is_read) {
+ if (is_read) {
+ while (s->datacnt > 0 && s->fifo_len < PL181_FIFO_LEN) {
+ value = 0;
+ for (n = 0; n < 4 && s->datacnt > 0; n++, s->datacnt--) {
value |= (uint32_t)sd_read_data(s->card) << (n * 8);
- n++;
- if (n == 4) {
- pl181_fifo_push(s, value);
- value = 0;
- n = 0;
- }
- } else {
- if (n == 0) {
- value = pl181_fifo_pop(s);
- n = 4;
- }
+ }
+ pl181_fifo_push(s, value);
+ }
+ } else {
+ while (s->datacnt > 0 && s->fifo_len > 0) {
+ value = pl181_fifo_pop(s);
+ for (n = 0; n < 4 && s->datacnt > 0; n++, s->datacnt--) {
sd_write_data(s->card, value & 0xff);
value >>= 8;
- n--;
- }
- s->datacnt--;
- }
- if (n && is_read) {
- pl181_fifo_push(s, value);
- }
+ }
+ }
+ }
}
s->status &= ~(PL181_STATUS_RX_FIFO | PL181_STATUS_TX_FIFO);
if (s->datacnt == 0) {
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