linux-kernel - Re: [git patches] libata fixes

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Message-ID: <4970DE4A.8030900@caviumnetworks.com>
Date:	Fri, 16 Jan 2009 11:21:46 -0800
From:	David Daney <ddaney@...iumnetworks.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Jeff Garzik <jeff@...zik.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-ide@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [git patches] libata fixes

Andrew Morton wrote:
> On Fri, 16 Jan 2009 10:27:21 -0500 Jeff Garzik <jeff@...zik.org> wrote:

>> +/**
>> + * Convert nanosecond based time to setting used in the
>> + * boot bus timing register, based on timing multiple
>> + */
> 
> There are comments in this file which use the kerneldoc token, but
> which aren't in kerneldoc format.
> 

I will endeavor to improve it.

>> +static unsigned int ns_to_tim_reg(unsigned int tim_mult, unsigned int nsecs)
>> +{
>> +	unsigned int val;
>> +
>> +	/*
>> +	 * Compute # of eclock periods to get desired duration in
>> +	 * nanoseconds.
>> +	 */
>> +	val = DIV_ROUND_UP(nsecs * (octeon_get_clock_rate() / 1000000),
>> +			  1000 * tim_mult);
>> +
>> +	return val;
>> +}
>>
> 
> There's great potential for overflows here, but I couldn't be bothered
> picking through it.  Are we sure that it's watertight?
> 

We are calculating timing register values, there will not be overflow
given that the delays are all under 1000nS and the clock rate will
never be greater than 10GHz.


> There's a 64-bit divide in there.  Will it link on 32-bit platforms?

It might not...

> 
> Or is this all 64-bit-only code?
> 

... but we are currently only supporting 64 bit kernels.


> wtf is an octeon anyway?  (greps).  Some MIPS thing.

Multicore MIPS64 SOC.

> I guess it's 64-bit-only.

Current, yes.  See above.

[...]
>> +/**
>> + * Called after libata determines the needed PIO mode. This
>> + * function programs the Octeon bootbus regions to support the
>> + * timing requirements of the PIO mode.
>> + *
>> + * @ap:     ATA port information
>> + * @dev:    ATA device
>> + */
> 
> That's getting more kerneldoccy, but isn't there yet.

As with the others, I will try to improve it.

[...]
>> +	T = (int)(2000000000000LL / octeon_get_clock_rate());
> 
> 64/64 divide.
> 

As with the case above, it works as only 64 bit kernel supported.

[...]
>> +static void octeon_cf_tf_read16(struct ata_port *ap, struct ata_taskfile *tf)
>> +{
>> +	u16 blob;
>> +	/* The base of the registers is at ioaddr.data_addr. */
>> +	void __iomem *base = ap->ioaddr.data_addr;
>> +
>> +	blob = __raw_readw(base + 0xc);
> 
> why __raw?
> 

readw() does byte swapping, we don't want that, hence the __raw.

[...]
>> +
>> +	cf_port = (struct octeon_cf_port *)ap->private_data;
> 
> Unneeded, undesirable cast of void* (multiple instances).
> 

I will fix it.


[...]
>>
>> +static irqreturn_t octeon_cf_interrupt(int irq, void *dev_instance)
>> +{
>> +	struct ata_host *host = dev_instance;
>> +	struct octeon_cf_port *cf_port;
>> +	int i;
>> +	unsigned int handled = 0;
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&host->lock, flags);
> 
> Would spin_lock() suffice here?

I have to think about that one.



Thanks for looking at it,
David daney

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