Re: esp_scsi QTAG in FAS216

[David Miller <davem@davemloft.net>]

From: Michael Schmitz <schmitzmic@gmail.com>
Date: Mon, 14 Apr 2014 10:38:09 +1200

> That appears to be our problem if I recall correctly Tuomas' debugging
> report. (reselection, not selection as initiator). As
> esp_slave_configure() enables queue tags regardless of chip config,
> we'd best make certain the chip is configured correctly.
> 
> The SCSI2 bit is used to test for presence of config register 2 in
> esp_get_revision but later cleared in the same function. It appears
> we'd need to set it after the call to scsi_esp_register() - can you
> test whether that obsoletes the zorro_esp_slave_configure hack,
> Tuomas?
 ...
>> Group 2 Commands
>> (seems to only be relevant for target mode).
>>
>> And about the QTE bit:
>>
>> Bit 6 Queue Tag Enable
>>
>> When this bit is set, the 53CF94/96 can receive 3-byte messages during
>> bus-initiated Select With ATN. This feature is also enabled by setting
>> bit 3 in the Configuration 2 register.
> 
> My preference would be to set this one (named ESP_CONFIG3_TBMS). Your
> opinion, Dave?

As seems to be agreed upon here, the SCSI2 bit in the CONFIG2 register
(ESP_CONFIG2_SCSI2ENAB) is only for when the chip is used in target
mode.  So it is not relevant for our discussion because this driver is
for initiator mode operation only.

But some pieces of documentation seem like they might not agree on
this point.

With respect to bit 3 in the config3 register, it can take on one of
two meaning depending upon chip revision.  As per ESP_CONFIG3_{TMS,FCLK}
it either controls fast SCSI clocking, or it enabled 3 byte message
recognition.

But oddly in the NCR53CX docs:

	http://www.ibiblio.org/pub/historic-linux/early-ports/Sparc/NCR/NCR53C9X.txt

it speaks as if ESP_CONFIG3_TMS and ESP_CONFIG3_TENB are merely finer
grained versions of config2 register setting ESP_CONFIG2_SCSI2ENAB,
which enables both features.

Again I looked at the FreeBSD driver and for all chips after plain
esp100, they set ESP_CONFIG2_SCSI2ENAB.

Can we try testing the following patch?

====================
esp_scsi: Set SCSI2 bit in config2 register.

This should allow proper recognition of 3 byte reselection
on all esp100a and later chips.

Reported-by: Kars de Jong <jongk@linux-m68k.org>
Reported-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
index 55548dc..16f69e0 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -2160,7 +2160,7 @@ static void esp_get_revision(struct esp *esp)
 		 */
 		esp->rev = ESP100;
 	} else {
-		esp->config2 = 0;
+		esp->config2 = ESP_CONFIG2_SCSI2ENAB;
 		esp_set_all_config3(esp, 5);
 		esp->prev_cfg3 = 5;
 		esp_write8(esp->config2, ESP_CFG2);
@@ -2187,8 +2187,6 @@ static void esp_get_revision(struct esp *esp)
 			} else {
 				esp->rev = ESP236;
 			}
-			esp->config2 = 0;
-			esp_write8(esp->config2, ESP_CFG2);
 		}
 	}
 }