linux-kernel - Re: [PATCH 2/3] spi: spacemit: introduce SpacemiT K1 SPI controller driver

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Message-ID: <000a41ee-a099-4944-8ef5-eed768f905cb@riscstar.com>
Date: Thu, 18 Sep 2025 10:58:30 -0500
From: Alex Elder <elder@...cstar.com>
To: Yixun Lan <dlan@...too.org>
Cc: broonie@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, linux-spi@...r.kernel.org, devicetree@...r.kernel.org,
 paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
 alex@...ti.fr, p.zabel@...gutronix.de, spacemit@...ts.linux.dev,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] spi: spacemit: introduce SpacemiT K1 SPI controller
 driver

On 9/18/25 9:39 AM, Yixun Lan wrote:
>>>> +	virt = drv_data->ioaddr + SSP_TOP_CTRL;
>>>> +	val = readl(virt);
>>>> +	val |= TOP_TRAIL;	/* Trailing bytes handled by DMA */
>>>> +	writel(val, virt);
>>> I'd prefer to do like this, it's more easy for people to grep..
>>> 	val = readl(drv_data->ioaddr + SSP_TOP_CTRL) | TOP_TRAIL;
>>> 	writel(val, drv_data->ioaddr + SSP_TOP_CTRL);
>> This is an idiom I use to make it very clear that:
>> - The address being read is exactly the same as what's being
>>     written
>> - The value read is being updated with bits/values
>>
>> I find that putting the "| TOP_TRAIL" on the same line as the
>> readl() call obscures things a bit.  Like my eye doesn't notice
>> it as readiliy somehow...
> fair, let's put it into another line
> 
>> Yours is a pure coding style comment.  There are two pieces, and
>> I'd like you to tell me how strongly you feel about them:
>> - Using virt to grab the address being written and read (versus
>>     just using drv_data->ioaddr + SSP_TOP_CTRL twice)
>> - Put the "| TOP_TRAIL" on the same line as the readl() (versus
>>     having that be assigned on a separate line).
>> To me, the second one is more important than the first.
>>
>> Let me know how strongly you feel about these and I'll update
>> my convention througout.
>>
> I'd strongly prefer not to introduce 'virt', so be something like this:
>   	val = readl(drv_data->ioaddr + SSP_TOP_CTRL);
>   	val |= TOP_TRAIL;
>   	writel(val, drv_data->ioaddr + SSP_TOP_CTRL);
> 

OK.  I'll do it this way throughout the driver in the
next version.

					-Alex