Archipelago » qemu

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];