linux-kernel - Re: [PATCH] spi: aspeed: Fix division by zero

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Date:   Mon, 13 Jun 2022 10:57:58 +0200
From:   Cédric Le Goater <clg@...d.org>
To:     Pratyush Yadav <p.yadav@...com>
CC:     <linux-spi@...r.kernel.org>, Mark Brown <broonie@...nel.org>,
        <linux-aspeed@...ts.ozlabs.org>, <openbmc@...ts.ozlabs.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Chin-Ting Kuo <chin-ting_kuo@...eedtech.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Ian Woloschin <ian.woloschin@...mai.com>
Subject: Re: [PATCH] spi: aspeed: Fix division by zero

On 6/13/22 10:39, Pratyush Yadav wrote:
> On 11/06/22 12:39PM, Cédric Le Goater wrote:
>> When using the normal read operation for data transfers, the dummy bus
>> width is zero. In that case, they are no dummy bytes to transfer and
>> setting the dummy field in the controller register becomes useless.
>>
>> Issue was found on a custom "Bifrost" board with a AST2500 SoC and
>> using a MX25L51245GMI-08G SPI Flash.
>>
>> Cc: Chin-Ting Kuo <chin-ting_kuo@...eedtech.com>
>> Reported-by: Ian Woloschin <ian.woloschin@...mai.com>
>> Fixes: 54613fc6659b ("spi: aspeed: Add support for direct mapping")
>> Signed-off-by: Cédric Le Goater <clg@...d.org>
>> ---
>>   drivers/spi/spi-aspeed-smc.c | 12 +++++++++++-
>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/spi/spi-aspeed-smc.c b/drivers/spi/spi-aspeed-smc.c
>> index 496f3e1e9079..3e891bf22470 100644
>> --- a/drivers/spi/spi-aspeed-smc.c
>> +++ b/drivers/spi/spi-aspeed-smc.c
>> @@ -558,6 +558,14 @@ static int aspeed_spi_dirmap_create(struct spi_mem_dirmap_desc *desc)
>>   	u32 ctl_val;
>>   	int ret = 0;
>>   
>> +	dev_dbg(aspi->dev,
>> +		"CE%d %s dirmap [ 0x%.8llx - 0x%.8llx ] OP %#x mode:%d.%d.%d.%d naddr:%#x ndummies:%#x\n",
>> +		chip->cs, op->data.dir == SPI_MEM_DATA_IN ? "read" : "write",
>> +		desc->info.offset, desc->info.offset + desc->info.length,
>> +		op->cmd.opcode, op->cmd.buswidth, op->addr.buswidth,
>> +		op->dummy.buswidth, op->data.buswidth,
>> +		op->addr.nbytes, op->dummy.nbytes);
>> +
> 
> Unrelated change. Please send as a separate patch.

OK.
  
>>   	chip->clk_freq = desc->mem->spi->max_speed_hz;
>>   
>>   	/* Only for reads */
>> @@ -574,9 +582,11 @@ static int aspeed_spi_dirmap_create(struct spi_mem_dirmap_desc *desc)
>>   	ctl_val = readl(chip->ctl) & ~CTRL_IO_CMD_MASK;
>>   	ctl_val |= aspeed_spi_get_io_mode(op) |
>>   		op->cmd.opcode << CTRL_COMMAND_SHIFT |
>> -		CTRL_IO_DUMMY_SET(op->dummy.nbytes / op->dummy.buswidth) |
>>   		CTRL_IO_MODE_READ;
>>   
>> +	if (op->dummy.nbytes)
>> +		ctl_val |= CTRL_IO_DUMMY_SET(op->dummy.nbytes / op->dummy.buswidth);
>> +
> 
> LGTM. With the above fixed,
>
> Reviewed-by: Pratyush Yadav <p.yadav@...com>

Thanks,

C.

> 
>>   	/* Tune 4BYTE address mode */
>>   	if (op->addr.nbytes) {
>>   		u32 addr_mode = readl(aspi->regs + CE_CTRL_REG);
>> -- 
>> 2.35.3
>>
>