Re: [PATCH 36/86] pata_it8213: add UDMA100 and UDMA133 support

[Sergei Shtylyov]

Hello.

Bartlomiej Zolnierkiewicz wrote:

> > Hello, I wrote:

> > > > There shouldn't be any problems with it as IDE it8213 host driver
> > > > has been supporting UDMA100 and UDMA133 for years.

> > > > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>

> > > > Index: b/drivers/ata/pata_it8213.c
> > > > ===================================================================
> > > > --- a/drivers/ata/pata_it8213.c
> > > > +++ b/drivers/ata/pata_it8213.c
> > > > @@ -164,7 +164,7 @@ static void it8213_set_dmamode (struct a
> > > >
> > > >         /* Clocks follow the PIIX style */
> > > >         u_speed = min(2 - (udma & 1), udma);
> > > > -        if (udma == 5)
> > > > +        if (udma > 4)
> > > >             u_clock = 0x1000;    /* 100Mhz */
> > > >         else if (udma > 2)
> > > >             u_clock = 1;        /* 66Mhz */
> > > > @@ -264,7 +264,7 @@ static int it8213_init_one (struct pci_d
> > > >         .flags        = ATA_FLAG_SLAVE_POSS,
> > > >         .pio_mask    = ATA_PIO4,
> > > >         .mwdma_mask    = ATA_MWDMA2,
> > > > -        .udma_mask     = ATA_UDMA4, /* FIXME: want UDMA 100? */
> > > > +        .udma_mask     = ATA_UDMA6,
> > > >         .port_ops    = &it8213_ops,
> > > >     };
> > > >     /* Current IT8213 stuff is single port */

> > >   Well, at 100 MHz it's probably not really UDMA6 but UDMA5 in 
> > > disguise... though u_speed would be 2 instead of 1 which should 
> > > correspond to either 3 clocks or 1 clock according to Intel's 
> > > documentation (different Intel docs give different figures and even ICH 
> > > PRM gives *both* clocks).

> >    If we take 3 clocks as correct (1 clock doesn't seem correct anyways, as 
> > with UDMA mode 5 UDMA cycle must be 20 ns and 1 clock gives only 10 ns). 
> > Well, then UDMA5 doesn't seem different from UDMA4 with ICH controllers and 
> > it's not clear why all the fuss about 100 MHz bit was necessary... :-/

   Unless it's 133 MHz bit in reality... :-)

> Sergei, please remember that IT8213 is a _custom_ spin-off from ICH chipset

   Well, I don't have IT8213 docs, so have to interpolate from PIIX/ICH 
documentation...

> and it gets some things in rather radically different way (i.e. value of PPE
> bit is reversed on IT8213).

   Perhaps then this bit shouldn't be called PPE (concerning your outher 
patch)?

> >    Returning to IT8213, with UDMA6 we have 'u_speed' of 2 that should 
> > correspond to 2 clocks which is 20 ns at 100 MHz and really is an UDMA5 
> > speed. Well, given UDMA5's slowness, that's definitely a gain. The question 
> > remains however, isn't this value reserved like on original ICH?

> It is not according to the official documentation for IT8213 (+ the chip

   Ah, good to know at least soembody has the damn datasheet! :-)

> officially claims to support UDMA6) and pata_it8213 behavior now matches
> the behavior of it8213 host driver.

   OK, fine then...

> I would love to be able to explain IT8213 chip internals in more detail
> but unfortunately the documentation is rather cryptic in this regard as
> it only gives you specific values that you should program into specific
> registers to get chip properly configured for specific transfer modes...

   At least something... :-)

> --
> Bartlomiej Zolnierkiewicz

MBR, Sergei
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