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

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Message-ID: <7a6efd1a-5920-60e5-bc68-dfbe6866e522@norrbonn.se>
Date:   Tue, 29 Jan 2019 15:56:31 +0100
From:   Jonas Bonn <jonas@...rbonn.se>
To:     Nicolas.Ferre@...rochip.com, linux-kernel@...r.kernel.org
Cc:     broonie@...nel.org, alexandre.belloni@...tlin.com,
        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 15:27, 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.

Thanks,
/Jonas