linux-kernel - Re: [PATCH V2] spi: tegra: add spi driver for SLINK controller

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Message-ID: <508F6906.7020704@nvidia.com>
Date:	Tue, 30 Oct 2012 11:13:34 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"spi-devel-general@...ts.sourceforge.net" 
	<spi-devel-general@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH V2] spi: tegra: add spi driver for SLINK controller

On Tuesday 30 October 2012 12:44 AM, Stephen Warren wrote:
> On 10/29/2012 11:18 AM, Laxman Dewangan wrote:
>> Tegra20/Tegra30 supports the spi interface through its SLINK
>> controller. Add spi driver for SLINK controller.
>> diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
>> +config SPI_TEGRA20_SLINK
>> +	tristate "Nvidia Tegra20/Tegra30 SLINK Controller"
>> +	depends on ARCH_TEGRA&&  TEGRA20_APB_DMA
> I think it depends on DMAENGINE, not the specific driver now, doesn't it?

Taking example from the mfd, we depends on particular driver, not from 
the core driver.
I like to have this depends on Tegra20_apb_dma.

>> +			x = 0;
>> +			for (i = 0; nbytes&&  (i<  tspi->bytes_per_word);
>> +							i++, nbytes--)
>> +				x |= ((*tx_buf++)<<  i*8);
>> +			tegra_slink_writel(tspi, x, SLINK_TX_FIFO);
>> +		}
>> +	}
> The if and the else there are basically identical now. Can't the else
> branch simply be replaced by the if branch? At most I think the
> difference comes down to max_n_32bit v.s. fifo_words_left calculations
> being slight different; everything else is the same.
>
> I suppose this isn't a big deal though; we could clean it up later if
> necessary.
>

I like to clean it later.


>> +		val |= SLINK_PACKED;
>> +		tegra_slink_writel(tspi, val, SLINK_DMA_CTL);
>> +		udelay(1);
>> +		wmb();
> Why the udelay() and wmb()?
udelay() is suggetsed by ASIC.
wmb() is lying in our downstream code and hence it is there but I dont 
think it is require now. I will remove it.


>> +static int tegra_slink_runtime_resume(struct device *dev)
>> +{
>> +	struct spi_master *master = dev_get_drvdata(dev);
>> +	struct tegra_slink_data *tspi = spi_master_get_devdata(master);
>> +
>> +	return tegra_slink_clk_prepare(tspi);
>> +}
> Why not move the body of tegra_slink_clk_{un,prepare} inside those
> functions, since they're only called from those functions?
>
Fine, I will do this,


>> +MODULE_ALIAS("platform:tegra_slink-slink");
> I think that's a typo.
Yes, I will correct it.


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