[PATCH 2.6.38.1] pata_it821x: Add module param to force UDMA on Vortex86SX

[PATCH 2.6.38.1] pata_it821x: Add module param to force UDMA on Vortex86SX

[igor]

 This patch adds parameter 'it8212_rdc11_force_udma' to 'pata_it821x' 
 module,
 which allows users to force UDMA mode on RDC11/Vortex86SX embedded 
 devices.

 ---
 UDMA is disabled by default due to some CRC errors, which i cannot 
 observe when
 using CompactFlash card with patched driver.

 May be there are errors with pure IDE devices or with older revisions 
 of Vortex86SX
 boards, i do no know. But for my device i have 2x improvement in I/O 
 speed when
 enabling UDMA/33 instead of MWDMA, so i think this parameter would be 
 useful.

 Also fix to initialize default value for parameter 'noraid'.

 --- b/drivers/ata/pata_it821x.c 2011-03-23 23:04:47.000000000 +0300
 +++ a/drivers/ata/pata_it821x.c 2011-03-26 15:10:49.608952573 +0300
 @@ -111,7 +111,8 @@ struct it821x_dev
   *     device.
   */

 -static int it8212_noraid;
 +static int it8212_noraid = 0;
 +static int it8212_rdc11_force_udma = 0;

  /**
   *     it821x_program  -       program the PIO/MWDMA registers
 @@ -913,7 +914,7 @@ static int it821x_init_one(struct pci_de

         if (pdev->vendor == PCI_VENDOR_ID_RDC) {
                 /* Deal with Vortex86SX */
 -               if (pdev->revision == 0x11)
 +               if (pdev->revision == 0x11 && !it8212_rdc11_force_udma)
                         ppi[0] = &info_rdc_11;
                 else
                         ppi[0] = &info_rdc;
 @@ -988,9 +989,12 @@ MODULE_LICENSE("GPL");
  MODULE_DEVICE_TABLE(pci, it821x);
  MODULE_VERSION(DRV_VERSION);

 -
  module_param_named(noraid, it8212_noraid, int, S_IRUGO);
  MODULE_PARM_DESC(noraid, "Force card into bypass mode");

 +module_param_named(rdc11_force_udma, it8212_rdc11_force_udma, int, 
 S_IRUGO|S_IWUSR);
 +MODULE_PARM_DESC(rdc11_force_udma, "Force enable UDMA mode 
 RDC11/Vortex86SX boards."
 +       " Use with caution");
 +
  module_init(it821x_init);
  module_exit(it821x_exit);

Re: [PATCH 2.6.38.1] pata_it821x: Add module param to force UDMA on Vortex86SX

[Alan Cox]

>  May be there are errors with pure IDE devices or with older revisions 
>  of Vortex86SX
>  boards, i do no know. But for my device i have 2x improvement in I/O 
>  speed when
>  enabling UDMA/33 instead of MWDMA, so i think this parameter would be 
>  useful.

"I do not know" is not a good basis for hacking storage code,
particularly if it was to turn out that the reason was something like
silent data corruption (eg as with UDMA on the old OSB4 controllers in
some cases)

The change came via DMP signoff (the manufacturer) so any adjustment of
this sort of checking really ought to go via DMP as well.

>  Also fix to initialize default value for parameter 'noraid'.

This does not need initialising - C guarantees static variables start at
zero. If that makes a difference you have other problems.

So NAK this.

Although if you want to take it up with DMP and find out if they have
updated rules or checks that want pushing that might be useful.

Alan

Re: [PATCH 2.6.38.1] pata_it821x: Add module param to force UDMA on Vortex86SX

[igor]

 On Sat, 26 Mar 2011 12:54:41 +0000, Alan Cox wrote:
>>  May be there are errors with pure IDE devices or with older 
>> revisions
>>  of Vortex86SX
>>  boards, i do no know. But for my device i have 2x improvement in 
>> I/O
>>  speed when
>>  enabling UDMA/33 instead of MWDMA, so i think this parameter would 
>> be
>>  useful.
>
> "I do not know" is not a good basis for hacking storage code,
> particularly if it was to turn out that the reason was something like
> silent data corruption (eg as with UDMA on the old OSB4 controllers 
> in
> some cases)
>

 Well, by "i do not know" i meant that i do not have other (older) DMP
 hardware, nor do i have means to connect pure IDE device to my device
 (DMP-2300).
 I just can state that i was having a root FS on a CompactFlash for 
 quite
 a long time with UDMA enabled, and i have not observed any problems, 
 and
 have seen no signs of data corruption either.

 I am just proposing to give users an option to enable UDMA at their own 
 risk,
 maybe add comment stating that enabling this option may or may not
 cause silent data corruption. Or maybe to add this as a sub-option to 
 the
 driver in Kconfig to switch on/off at compile time with detailed 
 description
 under ---help---

> The change came via DMP signoff (the manufacturer) so any adjustment 
> of
> this sort of checking really ought to go via DMP as well.
>
>>  Also fix to initialize default value for parameter 'noraid'.
>
> This does not need initialising - C guarantees static variables start 
> at
> zero. If that makes a difference you have other problems.

 Sorry, my bad.

> So NAK this.
>
> Although if you want to take it up with DMP and find out if they have
> updated rules or checks that want pushing that might be useful.

 No, i do not intend to contact them, i just wanted people to have an 
 on/off
 switch in kernel, not to push this patch by all means necessary.

 If this option is considered by community unneeded, i'll just have to 
 patch my
 own kernel with every upgrade :)

> Alan

Re: [PATCH 2.6.38.1] pata_it821x: Add module param to force UDMA on Vortex86SX

[Alan Cox]

> > Although if you want to take it up with DMP and find out if they have
> > updated rules or checks that want pushing that might be useful.
> 
>  No, i do not intend to contact them, i just wanted people to have an 
>  on/off
>  switch in kernel, not to push this patch by all means necessary.

If you want a patch in the upstream kernel then you need to do the
related work. If you can't even be bothered to follow up why an erratum
was added by the manufacturer then you've comprehensively missed the
standards we work to.

>  If this option is considered by community unneeded, i'll just have to 
>  patch my
>  own kernel with every upgrade :)

By all means. The GPL ensures you can do this and it means you won't
leave us with a one off potentially unsafe and unmaintained update.

Alan