Fwd: proposal for important kernel patch

[Andy Whitcroft]

On Wed, May 20, 2015 at 06:27:14AM -0600, Tim Gardner wrote:
> 
> 
> 
> -------- Forwarded Message --------
> Subject: proposal for important kernel patch
> Date: Wed, 20 May 2015 09:04:54 -0000
> From: Andrea Bravetti <andreabravetti at gmail.com>
> Reply-To: Andrea Bravetti <andreabravetti at gmail.com>
> To: Tim Gardner <tim.gardner at canonical.com>
> 
> I don't know how to propose an important kernel patch, so I ask you.
> 
> The first patch I would like to bring to your attention is this:
> 
> --- drivers/ata/libata-core.c   2015-05-11 18:49:06.699847395 +0200
> +++ drivers/ata/libata-core.c   2015-05-11 18:52:23.402510885 +0200
> @@ -4246,6 +4246,8 @@
>         { "WDC WD3000JD-*",             NULL,
> ATA_HORKAGE_WD_BROKEN_LPM },
>         { "WDC WD3200JD-*",             NULL,
> ATA_HORKAGE_WD_BROKEN_LPM },
> +       { "Samsung SSD 840*",           NULL,   ATA_HORKAGE_NO_NCQ_TRIM,
> },
> +
>         /* End Marker */
>         { }
>  };
> 
> Why is explained here:
> https://bugs.launchpad.net/ubuntu/+source/fstrim/+bug/1449005
> 
> Whitout this patch, or "libata.force=noncq", the Samsung SSD 840 is
> unusable with new firmware EXT0DB6Q: We lost a working day for this
> problem.

This first issue appears to be fixed by a couple of upstream HORKAGE
changes which appear to be marked for stable.  I have moved the bug listed
above over to the kernel package and marked it up for those fixes so we
can track them through the stable process.

> 
> The second one is a change in default kernel configuration:
> 
> --- .config     2015-05-20 10:28:41.709948652 +0200
> +++ .config     2015-05-20 09:23:13.332909672 +0200
> @@ -635,5 +635,5 @@
>  #
>  CONFIG_X86_PCC_CPUFREQ=y
> -CONFIG_X86_ACPI_CPUFREQ=y
> +CONFIG_X86_ACPI_CPUFREQ=m
>  CONFIG_X86_ACPI_CPUFREQ_CPB=y
>  CONFIG_X86_POWERNOW_K8=m
> 
> "acpi_cpufreq" should be built always as module and NEVER builtin
> because it prevent phc-linux being loaded, and also any other
> acpi_cpufreq replacement provided by the vendor if any.
> 
> "phc-linux" is very important if you need to downvolt some cpu.
> 
> Since I can't see any problem building it as a module and it should not
> cause any regression it should be made even on 14.04 LTS, and for any
> future release.
> 
> You can read about linux-phc here: http://www.linux-phc.org/forum
> 
> Also having linux-phc in the default kernel would be great but it may
> need some work.
> 
> It's important, especially for some ThinkPad notebook like the Edge 15
> 0301-J4G that hang frequently over 100C because of buggy voltage
> regulation, even new, clean fan, etc...
> 
> Not asking to fix in the mainstream kernel somethink so specific and
> hardware bug related, but please please please don't force anyone has
> this problem to rebuild a custom kernel because it's very annoying, just
> build acpi_cpufreq as module and not builtin.

I think this is built-in becuase it did not use to be autoloadable.  We
should investigate if that is still true.

-apw