linux-kernel - Re: [PATCH v2 4/4] spi: amd: Don't wait for a write-only transfer to finish

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Date:   Fri, 10 Sep 2021 14:11:12 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Lucas tanure <tanureal@...nsource.cirrus.com>
CC:     Mark Brown <broonie@...nel.org>,
        Sanjay R Mehta <sanju.mehta@....com>,
        Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@....com>,
        <linux-kernel@...r.kernel.org>, <linux-spi@...r.kernel.org>,
        <patches@...nsource.cirrus.com>
Subject: Re: [PATCH v2 4/4] spi: amd: Don't wait for a write-only transfer to
 finish

On Fri, Sep 10, 2021 at 02:47:32PM +0100, Lucas tanure wrote:
> On 9/10/21 1:42 PM, Charles Keepax wrote:
> >On Fri, Sep 10, 2021 at 12:15:29PM +0100, Lucas Tanure wrote:
> >>Return from a write-only transfer without waiting for
> >>it to finish
> >>But wait before a new transfer as the previous may
> >>still happening and also wait before reading the data
> >>from the FIFO
> >>
> >>Signed-off-by: Lucas Tanure <tanureal@...nsource.cirrus.com>
> >>---
> >>  static int amd_spi_master_setup(struct spi_device *spi)
> >>@@ -178,6 +185,7 @@ static inline int amd_spi_fifo_xfer(struct amd_spi *amd_spi,
> >>  			amd_spi_clear_fifo_ptr(amd_spi);
> >>  			/* Execute command */
> >>  			amd_spi_execute_opcode(amd_spi);
> >>+			amd_spi_busy_wait(amd_spi);
> >
> >Surely the previous transfer can't still be happening if this if
> >unconditional? Should this not be gated on rx_len?
> >
> >Thanks,
> >Charles
> >
> >>  			/* Read data from FIFO to receive buffer  */
> >>  			for (i = 0; i < rx_len; i++)
> >>  				buf[i] = amd_spi_readreg8(amd_spi, AMD_SPI_FIFO_BASE + tx_len + i);
> >>-- 
> >>2.33.0
> >>
> This is executed inside an xfer->rx_buf not null if, so it`s gated
> in a read transfer and not for a write transfer only
> 

And so it is, sorry should have looked at more than just the git
context there.

Reviewed-by: Charles Keepax <ckeepax@...nsource.cirrus.com>

Thanks,
Charles