linux-kernel - Re: libata pata_pdc2027x success on sparc64

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Message-ID: <44C8EB3C.4080404@ru.mvista.com>
Date:	Thu, 27 Jul 2006 20:35:08 +0400
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	albertl@...l.com
Cc:	Mikael Pettersson <mikpe@...uu.se>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org, alan@...hat.com,
	Unicorn Chang <uchang@...ibm.com>, Doug Maxey <dwm@...yolf.org>
Subject: Re: libata pata_pdc2027x success on sparc64

Hello.

Albert Lee wrote:

>>>In contrast, the old IDE pdc202xx_new driver had lots
>>>of problems with CRC errors causing it to disable DMA.

>>   Hm, from my experience it usually falls back to UltraDMA/44 and then
>>the thing startrt working...

>>>I wasn't able to manually tune it above udma3 without
>>>getting more errors. This isn't sparc64-specific: I've
>>>had similar negative experience with the old IDE Promise
>>>drivers in a PowerMac.

>>   This happens because the "old" driver misses the PLL calibration code.
>>   You may want to try these Albert's patches:

>>http://marc.theaimsgroup.com/?t=110992452800002&r=1&w=2
>>http://marc.theaimsgroup.com/?t=110992471500002&r=1&w=2
>>http://marc.theaimsgroup.com/?t=110992490100002&r=1&w=2
>>http://marc.theaimsgroup.com/?t=111019238400003&r=1&w=2

>>   It looks like they were never considered for accepting into the kernel
>>while they succesfully solve this issue. Maybe Albert could try pushing
>>them into -mm tree once more?

> The libata version has three improvements compared to the IDE version.

> 1. The PLL calibration patches in the above URLs (for IDE)
> still need more improvement as done in the pdc_read_counter()
> of the libata version.

    Indeed. When backporting your patches to 2.6.10, I've added alike 
function, so can generate an extra patch against those.

> 2. The Promise 2027x adapters check the "set features - xfer mode"
>    and set the timing register automatically. However, the automatically
>    set values are not correct under 133MHz. Libata has a hook
>    pdc2027x_post_set_mode() to set the values back by software.

    You probably forgot -- the last mentioned patch was all about it. :-)

> 3. ATAPI DMA is supported (please see pdc2027x_check_atapi_dma()).
>    Maybe we also need to add this to the IDE version.

    Wouldn't hurt. :-)

> Currently I have no time to update the IDE pdc202xx_new driver.

    I'll probably take this on then, starting with pushing this half-buried 
stuff into -mm tree.

> Also as Alan said, we have no maintainer for the IDE layer at this time.
> So, if ok, please try to use the libata-based driver.

WBR, Sergei
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