linux-kernel - Re: [PATCH] pata_at91: SMC settings calculation bugfixes, support for t6z and IORDY

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Date:	Fri, 13 May 2011 09:13:00 +0200
From:	Stanislaw Gruszka <stf_xl@...pl>
To:	Igor Plyatov <plyatov@...il.com>
Cc:	Jeff Garzik <jgarzik@...ox.com>, Tejun Heo <tj@...nel.org>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pata_at91: SMC settings calculation bugfixes, support
 for t6z and IORDY

Hello

On Thu, May 12, 2011 at 10:15:51PM +0400, Igor Plyatov wrote:
> * New code correctly calculates SMC registers values, adjusts calculated
>   to admissible ranges, enlarges cycles when required and converts values
>   into SMC's format.
> * Support for TDF cycles (ATA t6z) and IORDY line added.
> * Eliminate need in the initial_timing structure.
> * Code cleanup.

Generally looks good for me, some remarks below.

> +		int *setup, int *pulse, int *cycle, int *cs_pulse)
> +{
> +	int ret_val;
> +	int err = 0;
> +	struct smc_range range_setup[] = {	/* SMC_SETUP valid values */
> +		{.min = 0,	.max = 31},	/* first  range */
> +		{.min = 128,	.max = 159}	/* second range */
> +	};
> +	struct smc_range range_pulse[] = {	/* SMC_PULSE valid values */
> +		{.min = 0,	.max = 63},	/* first  range */
> +		{.min = 256,	.max = 319}	/* second range */
> +	};
> +	struct smc_range range_cycle[] = {	/* SMC_CYCLE valid values */
> +		{.min = 0,	.max = 127},	/* first  range */
> +		{.min = 256,	.max = 383},	/* second range */
> +		{.min = 512,	.max = 639},	/* third  range */
> +		{.min = 768,	.max = 895}	/* fourth range */
> +	};

These /* ... rage */ comments are useless.

> +	*cs_pulse = *cycle;
> +	if (*cs_pulse > CS_PULSE_MAXIMUM) {
> +		dev_err(dev, "unable to calculate valid SMC settings\n");
> +		return -ER_SMC_CALC;
> +	}
> +
> +	ret_val = adjust_smc_value(cs_pulse, range_pulse,
> +					ARRAY_SIZE(range_pulse));
> +	if (ret_val < 0) {
> +		dev_warn(dev, "maximal SMC CS Pulse value\n");
> +	} else if (ret_val != 0) {
> +		*cycle = *cs_pulse;

cs_pulse and cycle will always have the same value here, so perhaps only
one variable can be used instead of two.

> + * to_smc_format - convert values into SMC format
> + * @setup: SETUP value of SMC Setup Register
> + * @pulse: PULSE value of SMC Pulse Register
> + * @cycle: CYCLE value of SMC Cycle Register
> + * @cs_pulse: NCS_PULSE value of SMC Pulse Register
> + */
> +static void to_smc_format(int *setup, int *pulse, int *cycle, int *cs_pulse)
> +{
> +	*setup = (*setup & 0x1f) | ((*setup & 0x80) >> 2);
> +	*pulse = (*pulse & 0x3f) | ((*pulse & 0x100) >> 2);
> +	*cycle = (*cycle & 0x7f) | ((*cycle & 0x300) >> 1);
> +	*cs_pulse = (*cs_pulse & 0x3f) | ((*cs_pulse & 0x100) >> 2);

Ok, here is the difference, but in previous functions cs_pulse seems
to be unneeded.

> +	do {
> +		ret = calc_smc_vals(dev, &setup, &pulse, &cycle, &cs_pulse);
> +	} while (ret == -ER_SMC_RECALC);

I do not quite understand why we have to recalculate, could you
add a short comment or explain?

Thanks
Stanislaw
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