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

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Message-ID: <4B0EC492.4060503@ru.mvista.com>
Date:	Thu, 26 Nov 2009 21:10:26 +0300
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 36/86] pata_it8213: add UDMA100 and UDMA133 support

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@...il.com>

>>>>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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