linux-kernel - Re: [PATCH v3 5/6] spi: at91-usart: add driver for at91-usart as spi

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Date:   Wed, 23 May 2018 11:10:28 +0300
From:   Radu Pirea <radu.pirea@...rochip.com>
To:     Mark Brown <broonie@...nel.org>
CC:     <devicetree@...r.kernel.org>, <linux-serial@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-spi@...r.kernel.org>, <mark.rutland@....com>,
        <robh+dt@...nel.org>, <lee.jones@...aro.org>,
        <gregkh@...uxfoundation.org>, <jslaby@...e.com>,
        <richard.genoud@...il.com>, <alexandre.belloni@...tlin.com>,
        <nicolas.ferre@...rochip.com>
Subject: Re: [PATCH v3 5/6] spi: at91-usart: add driver for at91-usart as spi



On 05/17/2018 08:04 AM, Mark Brown wrote:
> On Fri, May 11, 2018 at 01:38:21PM +0300, Radu Pirea wrote:
> 
>> +config SPI_AT91_USART
>> +        tristate "Atmel USART Controller as SPI"
>> +	depends on HAS_DMA
>> +	depends on (ARCH_AT91 || COMPILE_TEST)
>> +        select MFD_AT91_USART
>> +	help
>> +	  This selects a driver for the AT91 USART Controller as SPI Master,
>> +	  present on AT91 and SAMA5 SoC series.
>> +
> 
> This looks like there's some tab/space mixing going on here.
> 
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Driver for AT91 USART Controllers as SPI
>> + *
>> + * Copyright (C) 2018 Microchip Technology Inc.
> 
> Make the entire block a C++ comment so it looks more intentional rather
> tha mixing C and C++.

Hi Mark,

I know it's ugly, but SPDX license identifier must be in a separate 
comment block.

> 
>> +static inline void at91_usart_spi_tx(struct at91_usart_spi *aus)
>> +{
>> +	unsigned int len = aus->current_transfer->len;
>> +	unsigned int remaining = aus->current_tx_remaining_bytes;
>> +	const u8  *tx_buf = aus->current_transfer->tx_buf;
>> +
>> +	if (tx_buf && remaining) {
>> +		if (at91_usart_spi_tx_ready(aus))
>> +			spi_writel(aus, THR, tx_buf[len - remaining]);
>> +			aus->current_tx_remaining_bytes--;
> 
> Missing braces here - we only write to the FIFO if there's space but we
> unconditionally decrement the counter.
> 

Thanks. I will fix it.

>> +	} else {
>> +		if (at91_usart_spi_tx_ready(aus))
>> +			spi_writel(aus, THR, US_DUMMY_TX);
>> +	}
>> +}
> 
> This looks like you're open coding SPI_CONTROLLER_MUST_TX
> 
>> +	int len = aus->current_transfer->len;
>> +	int remaining = aus->current_rx_remaining_bytes;
>> +	u8  *rx_buf = aus->current_transfer->rx_buf;
>> +
>> +	if (aus->current_rx_remaining_bytes) {
>> +		rx_buf[len - remaining] = spi_readb(aus, RHR);
>> +		aus->current_rx_remaining_bytes--;
>> +	} else {
>> +		spi_readb(aus, RHR);
>> +	}
> 
> Similarly for _MUST_RX.
> 
>> +	controller->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
> 
> You're actually setting both flags...  this means that the handling for
> cases with missing TX or RX buffers can't happen.

Sorry. My mistake. I will remove unnecessary code.