From mboxrd@z Thu Jan  1 00:00:00 1970
From: Finn Thain <fthain@telegraphics.com.au>
Subject: Re: m68k v3.16 status update
Date: Wed, 20 Dec 2017 10:01:35 +1100 (AEDT)
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To: Michael Schmitz <schmitzmic@gmail.com>
Cc: Vainikka Tuomas <tuomas.vainikka@aalto.fi>, Geert Uytterhoeven <geert@linux-m68k.org>, linux-m68k <linux-m68k@vger.kernel.org>

On Tue, 19 Dec 2017, Michael Schmitz wrote:

> 
> esp->command_block_dma is mapped at driver init time so we don't get to 
> chose at command submission time.

When the command is submitted, ops->send_dma_cmd() can do something like 
this,

static void zorro_esp_send_dma_cmd(struct esp *esp, u32 dma_addr, u32 esp_count,
                                   u32 dma_count, int write, u8 cmd);
{
	if ((dma_addr_t)dma_addr == esp->command_block_dma && esp_count < 4) {
		zorro_esp_send_pio_cmd(esp, (u32)esp->command_block, esp_count,
		                       dma_count, write, cmd);
		return;
	}

	/* do the usual DMA... */
}

This logic completely ignores data transfers (including sense transfers) 
but it is simple and self-contained and should get the job done.

>>From what you said, I think you already arrived at this code (or something 
equivalent). Is there a problem? Do we have to do PIO data transfers too?

--