linux-kernel - Re: [PATCH v4 2/2] spi-atmel: support inter-word delay

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Message-ID: <20190129150549.GA19959@piout.net>
Date:   Tue, 29 Jan 2019 16:05:49 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Jonas Bonn <jonas@...rbonn.se>
Cc:     Nicolas.Ferre@...rochip.com, linux-kernel@...r.kernel.org,
        broonie@...nel.org, Ludovic.Desroches@...rochip.com,
        linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Tudor.Ambarus@...rochip.com
Subject: Re: [PATCH v4 2/2] spi-atmel: support inter-word delay

Hi,

On 29/01/2019 15:56:31+0100, Jonas Bonn wrote:
> On 29/01/2019 15:27, Nicolas.Ferre@...rochip.com wrote:
> > On 29/01/2019 at 09:38, Jonas Bonn wrote:
> > > 
> > > +	/* DLYBCT adds delays between words.  This is useful for slow devices
> > > +	 * that need a bit of time to setup the next transfer.
> > > +	 */
> > > +	if (spi->word_delay_us) {
> > 
> > Well...
> > 
> > > +		csr |= SPI_BF(DLYBCT,
> > > +			clamp_t(u8,
> > > +				(as->spi_clk/1000000*spi->word_delay_us)>>5,
> > > +				1, 255));
> > 
> > ... why not simplifying to:
> > +				0, 255));
> > and remove the test altogether, after all?
> 
> Hmm... that seemed too easy!  This started out as something else and looking
> at it now I think even the clamp_t() is unnecessary.  The value is already
> 0-255 and the way SPI_BF works any overflow is already truncated...  I'll
> rework this and resubmit once I get some feedback on the word_delay_us bits.
> 

While at it, note that you need to add spaces around the operators.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com