linux-kernel - Re: [PATCH v2 2/6] spi: microchip-core: Refactor FIFO read and write handlers

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Message-ID: <aSiBbS4uboYehB-8@smile.fi.intel.com>
Date: Thu, 27 Nov 2025 18:50:53 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Prajna Rajendra Kumar <prajna.rajendrakumar@...rochip.com>
Cc: Mark Brown <broonie@...nel.org>, david laight <david.laight@...box.com>,
	linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Conor Dooley - M52691 <Conor.Dooley@...rochip.com>
Subject: Re: [PATCH v2 2/6] spi: microchip-core: Refactor FIFO read and write
 handlers

On Thu, Nov 27, 2025 at 06:49:31PM +0200, Andy Shevchenko wrote:
> On Thu, Nov 27, 2025 at 04:08:25PM +0000, Prajna Rajendra Kumar wrote:
> > On 26/11/2025 12:13, Andy Shevchenko wrote:
> > > On Wed, Nov 26, 2025 at 12:05:22PM +0000, Mark Brown wrote:
> > > > On Wed, Nov 26, 2025 at 09:21:45AM +0000, david laight wrote:

...

> > > > > I'm not sure I don't prefer the version with one writeb() call.
> > > > > How about:
> > > > >              writeb(spi->tx_buf ? *spi->tx_buf++ : 0xaa,
> > > > >                      spi->regs + MCHP_CORESPI_REG_TXDATA);
> > > > Please don't abuse the ternery operator like this, just write normal
> > > > conditional statements.
> > > FWIW, that's what my patch does already :-)
> > 
> > Thanks for the series. However, this particular patch appears to
> > introduce a regression. The SPI controller reads an incorrect
> > Device ID from the peripheral.
> 
> Hmm... This is interesting. The only thing I see is missed dummy byte read in
> case of TX only transfers. Is this what you have?

So, the

	else
		readb(spi->regs + MCHP_CORESPI_REG_RXDATA);

should help if it's the case.

But the change can be updated to still have the "data" be always assigned as
in the original code.

> > I’m investigating the root cause and will follow up.
> 
> Okay, I will be glad to know the cause and help to fix that.
> 
> 
> Thank you for the review!

-- 
With Best Regards,
Andy Shevchenko