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From: John David Anglin <dave.anglin@bell.net>
To: Carlo Pisani <carlojpisani@gmail.com>
Cc: Parisc List <linux-parisc@vger.kernel.org>
Subject: Re: C3600, sata controller
Date: Mon, 13 May 2019 21:50:25 -0400
Message-ID: <3fd05da8-3601-a0b3-a212-2c72710520c4@bell.net> (raw)
In-Reply-To: <CA+QBN9CPdm2q9FMzo0nOq__XZ=0Rf98pnXSG9fUjpXaUbq0skA@mail.gmail.com>

On 2019-05-13 7:47 p.m., Carlo Pisani wrote:
> So levels should be compatible, but so what is the difference between
> 64-bit PCI slot and PCI-X slot?
There is no difference in the slots except PCI-X slots are always 3.3V and a 5V card won't work in them.
The difference is in the bus protocol and timing.

This is what I see in wikipedia:

"In PCI, a transaction that cannot be completed immediately is postponed by either the target or the initiator issuing retry-cycles, during
which no other agents can use the PCI bus. Since PCI lacks a split-response mechanism to permit the target to return data at a later time, the
bus remains occupied by the target issuing retry-cycles until the read data is ready. In PCI-X, after the master issues the request, it
disconnects from the PCI bus, allowing other agents to use the bus. The split-response containing the requested data is generated only when the
target is ready to return all of the requested data. Split-responses increase bus efficiency by eliminating retry-cycles, during which no data
can be transferred across the bus.

PCI also suffered from the relative scarcity of unique interrupt lines. With only 4 interrupt lines (INTA/B/C/D), systems with many PCI devices
require multiple functions to share an interrupt line, complicating host-side interrupt-handling. PCI-X added Message Signaled Interrupts
<https://en.wikipedia.org/wiki/Message_Signaled_Interrupts>, an interrupt system using writes to host-memory. In MSI-mode, the function's
interrupt is not signaled by asserting an INTx line. Instead, the function performs a memory-write to a system-configured region in host-memory.
Since the content and address are configured on a per-function basis, MSI-mode interrupts are dedicated instead of shared. A PCI-X system allows
both MSI-mode interrupts and legacy INTx interrupts to be used simultaneously (though not by the same function.)

The lack of registered I/Os limited PCI to a maximum frequency of 66 MHz. PCI-X I/Os are registered to the PCI clock, usually through means of a
PLL to actively control I/O delay the bus pins. The improvement in setup time allows an increase in frequency to 133 MHz."

Nominally, one would think a PCI-X card would fall back to PCI mode but maybe this needs firmware
support.

I still think the 3.3V signalling of a PCI-X card likely is incompatible with 5V signalling in c3600.  A 5V
card won't work in a PCI-X slot.  Only slot SL2 is 3.3V.

Wiki also says:

"Many 64-bit PCI-X cards are designed to work in 32-bit mode if inserted in shorter 32-bit connectors, with some loss of speed.[19][20] An
example of this is the Adaptec 29160 64-bit SCSI interface card.[21] However some 64-bit PCI-X cards do not work in standard 32-bit PCI slots.[22]"

So, I think you can only use 5V or universal conventional PCI cards in c3600 (except for slot SL2).

Here are some Adaptec 64-bit cards that I found.
https://storage.microsemi.com/en-us/support/raid/sata/aar-2410sa/
https://storage.microsemi.com/en-us/support/raid/sata/aar-21610sa/

Dave
-- 

John David Anglin  dave.anglin@bell.net


  reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-01 21:45 linux-next: Signed-off-by missing for commit in the parisc-hd tree Stephen Rothwell
2019-05-02  5:48 ` Helge Deller
2019-05-12 20:44   ` C3600, sata controller Carlo Pisani
2019-05-12 20:49     ` Carlo Pisani
2019-05-12 21:10     ` John David Anglin
2019-05-12 21:15       ` Carlo Pisani
2019-05-13 23:14         ` John David Anglin
2019-05-13 23:24           ` Carlo Pisani
2019-05-13 23:47             ` Carlo Pisani
2019-05-14  1:50               ` John David Anglin [this message]
2019-05-14  8:22                 ` Carlo Pisani
     [not found]                 ` <CA+QBN9CgMRFmv+isvH-Y=FCCFwKhmD5_5s5u32xg+wk-gTLK5A@mail.gmail.com>
2019-05-14 12:10                   ` John David Anglin
2019-05-14 12:29                     ` Carlo Pisani
2019-05-14 12:57                       ` C3600, optical Fibre Channel, any card? Carlo Pisani
2019-05-14 13:01                       ` C3600, sata controller Sven Schnelle
2019-05-14 14:23                         ` John David Anglin
2019-05-17 15:43                           ` Carlo Pisani
2019-05-17 17:21                             ` Helge Deller
2019-05-17 18:05                               ` John David Anglin
2019-05-17 18:25                                 ` Carlo Pisani
2019-05-13 15:10     ` Carlo Pisani
2019-05-13 21:58       ` Carlo Pisani
2019-05-17 17:31     ` Carlo Pisani
2019-05-25  8:59     ` Carlo Pisani

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