Re: [PM][PATCH v3 2/4] OMAP3: Serial: Errata i202: fix for MDR1 access

From: Govindraj <govindraj.ti@gmail.com>
To: "Kattungal, Deepak" <deepak.k@ti.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>,
	"Menon, Nishanth" <nm@ti.com>,
	linux-omap <linux-omap@vger.kernel.org>,
	"Raja, Govindraj" <govindraj.raja@ti.com>,
	Tero Kristo <tero.kristo@nokia.com>
Subject: Re: [PM][PATCH v3 2/4] OMAP3: Serial: Errata i202: fix for MDR1 access
Date: Thu, 6 May 2010 15:24:43 +0530	[thread overview]
Message-ID: <u2id6a0f7aa1005060254v17bb0018seb3ddb90e6221e4a@mail.gmail.com> (raw)
In-Reply-To: <FCCFB4CDC6E5564B9182F639FC3560870304F5B1AE@dbde02.ent.ti.com>

On Thu, May 6, 2010 at 5:49 AM, Kattungal, Deepak <deepak.k@ti.com> wrote:
> Hi Kevin,
>
> My Comments as below.
>
> Regards
> Deepak
>
> -----Original Message-----
> From: Kevin Hilman [mailto:khilman@deeprootsystems.com]
> Sent: Wednesday, May 05, 2010 6:55 PM
> To: Menon, Nishanth
> Cc: linux-omap; Kattungal, Deepak; Raja, Govindraj; Tero Kristo
> Subject: Re: [PM][PATCH v3 2/4] OMAP3: Serial: Errata i202: fix for MDR1 access
>
> Nishanth Menon <nm@ti.com> writes:
>
>> From: Deepak K <deepak.k@ti.com>
>>
>> Original patch:
>> http://git.omapzoom.org/?p=kernel/omap.git;a=commitdiff;h=42d4a342c009bd9727c100abc8a4bc3063c22f0c
>>
>> Errata i202 (OMAP3430 - 1.12, OMAP3630 - 1.6):
>
> This workaround is currently done for all OMAPs.
>
> Presumably, this errata will eventually be fixed.  So, as with other
> errata fixes, we need some sort of SoC-rev based flag and the errata
> workaround done based on that flag.
>
> Deepak : This would be a good fix, thanks for the suggestion.
>
> Also, shouldn't there be a fix for this in the 8250 and omap-serial
> drivers too?
>
>
> Deepak : The 8250 is not using the MDR Register. This would be needed only by the omap-serial. The 8250 being a general driver we may not require the access to MDR1 register. Hence the fix not required for 8250.
>

Why do you say this fix is not necessary for 8250?

Isn't the omap_uart_reset configuring uart for 16x mode?

Context save and restore is an common for whether it is 8250 or omap-serial.c

The only difference here wrt to MDR and 8250 is
-> MDR though not accesed by 8250 currently serial.c sets it to uart16x mode.

In omap-serial.c we configure MDR based on baudrate as we have an uart13x mode
which is ignored in 8250 and thus 8250 may not support 13x baud's correctly
which is taken care in omap-serial.

I think this patch is fine and only concern is to make it applicable
to appropriate socs as kevin said.

---
Regards,
Govindraj.R
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