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The ESP SCSI driver currently doesn't check whether a DMA requests has
completed before checking its status. On older qemu versions this works ok
because DMA happens instantly. On never qemu DMA can take an indeterminate
amount of time ooto complete, just like on real hardware.
The patch below waits for the controller to raise the DMA interrupt after
initiating a DMA request.
Index: drivers/esp.c
===================================================================
--- drivers/esp.c (revision 61)
+++ drivers/esp.c (working copy)
@@ -113,6 +113,8 @@ do_command(esp_private_t *esp, sd_privat
esp->espdma.regs->cond_reg = 0;
// Set ATN, issue command
esp->ll->regs[ESP_CMD] = ESP_CMD_SELA | ESP_CMD_DMA;
+ // Wait for DMA to complete
+ while ((esp->espdma.regs->cond_reg & DMA_HNDL_INTR) == 0) /* no-op */;
// Check status
status = esp->ll->regs[ESP_STATUS];
@@ -129,6 +131,8 @@ do_command(esp_private_t *esp, sd_privat
esp->espdma.regs->cond_reg = DMA_ST_WRITE;
// Transfer
esp->ll->regs[ESP_CMD] = ESP_CMD_TI | ESP_CMD_DMA;
+ // Wait for DMA to complete
+ while ((esp->espdma.regs->cond_reg & DMA_HNDL_INTR) == 0) /* no-op */;
// Check status
status = esp->ll->regs[ESP_STATUS];
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