The ESP SELATN command used to send SCSI commands from the ESP to the SCSI bus
is not a DMA command and therefore does not affect the STAT_TC bit. The only
reason this works at all is due to a bug in QEMU which (currently) always
updates the STAT_TC bit in ESP_RSTAT regardless of the state of the ESP_CMD_DMA
bit.
According to the NCR datasheet [1] the INTR_BS/INTR_FC bits are set when the
SELATN command has completed, so update the existing logic to check for these
bits in ESP_RINTR instead. Note that the read of ESP_RINTR needs to be
restricted to state == 0 as reading ESP_RINTR resets the ESP_RSTAT register
which breaks the STAT_TC check when state == 1.
This commit also includes an extra read of ESP_INTR to clear all the interrupt
bits before submitting the SELATN command to ensure that we don't accidentally
immediately progress to the data phase handling logic where ESP_RINTR bits have
already been set by a previous ESP command.
[1] "NCR 53C94, 53C95, 53C96 Advanced SCSI Controller"
NCR_53C94_53C95_53C96_Data_Sheet_Feb90.pdf
Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk>
---
src/hw/esp-scsi.c | 36 ++++++++++++++++++++++--------------
1 file changed, 22 insertions(+), 14 deletions(-)
diff --git a/src/hw/esp-scsi.c b/src/hw/esp-scsi.c
index e4815aa..2d2d915 100644
--- a/src/hw/esp-scsi.c
+++ b/src/hw/esp-scsi.c
@@ -57,6 +57,8 @@
#define ESP_STAT_MSG 0x04
#define ESP_STAT_TC 0x10
+#define ESP_INTR_FC 0x08
+#define ESP_INTR_BS 0x10
#define ESP_INTR_DC 0x20
struct esp_lun_s {
@@ -97,8 +99,9 @@ esp_scsi_process_op(struct disk_op_s *op)
outb(target, iobase + ESP_WBUSID);
- /* Clear FIFO before sending command. */
+ /* Clear FIFO and interrupts before sending command. */
outb(ESP_CMD_FLUSH, iobase + ESP_CMD);
+ inb(iobase + ESP_RINTR);
/*
* We need to pass the LUN at the beginning of the command, and the FIFO
@@ -115,22 +118,27 @@ esp_scsi_process_op(struct disk_op_s *op)
for (state = 0;;) {
u8 stat = inb(iobase + ESP_RSTAT);
+ u8 intr;
- /* Detect disconnected device. */
- if (state == 0 && (inb(iobase + ESP_RINTR) & ESP_INTR_DC)) {
- return DISK_RET_ENOTREADY;
- }
+ if (state == 0) {
+ intr = inb(iobase + ESP_RINTR);
- /* HBA reads command, clears CD, sets TC -> do DMA if needed. */
- if (state == 0 && (stat & ESP_STAT_TC)) {
- state++;
- if (op->count && blocksize) {
- /* Data phase. */
- u32 count = (u32)op->count * blocksize;
- esp_scsi_dma(iobase, (u32)op->buf_fl, count, scsi_is_read(op));
- outb(ESP_CMD_TI | ESP_CMD_DMA, iobase + ESP_CMD);
- continue;
+ /* Detect disconnected device. */
+ if (intr & ESP_INTR_DC) {
+ return DISK_RET_ENOTREADY;
}
+
+ /* HBA reads command, executes it, sets BS/FC -> do DMA if needed.
*/
+ if (intr & (ESP_INTR_BS | ESP_INTR_FC)) {
+ state++;
+ if (op->count && blocksize) {
+ /* Data phase. */
+ u32 count = (u32)op->count * blocksize;
+ esp_scsi_dma(iobase, (u32)op->buf_fl, count,
scsi_is_read(op));
+ outb(ESP_CMD_TI | ESP_CMD_DMA, iobase + ESP_CMD);
+ continue;
+ }
+ }
}
/* At end of DMA TC is set again -> complete command. */
--
2.39.2
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