linux-kernel - Re: [PATCH v3 2/3] spi: spi-cadence: supports transmission with bits_per

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Message-ID: <lbijvnnwsnddonmm5pveqzap6iibxhl4maneq43x4j6w64dev6@u75qhm5cwiob>
Date: Wed, 14 Jan 2026 16:09:39 +0000
From: Rodrigo Alencar <455.rodrigo.alencar@...il.com>
To: Mark Brown <broonie@...nel.org>, 
	Rodrigo Alencar <455.rodrigo.alencar@...il.com>
Cc: Jun Guo <jun.guo@...tech.com>, peter.chen@...tech.com, 
	fugang.duan@...tech.com, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	linux-spi@...r.kernel.org, michal.simek@....com, cix-kernel-upstream@...tech.com, 
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] spi: spi-cadence: supports transmission with
 bits_per_word of 16 and 32

On 26/01/14 02:16PM, Mark Brown wrote:
> On Wed, Jan 14, 2026 at 02:14:35PM +0000, Rodrigo Alencar wrote:
> > On 25/10/31 03:30PM, Jun Guo wrote:
> 
> > > +	if (xspi->txbuf) {
> > > +		switch (xspi->n_bytes) {
> > > +		case CDNS_SPI_N_BYTES_U8:
> > > +			txw = *(u8 *)xspi->txbuf;
> > > +			break;
> 
> > > +		cdns_spi_write(xspi, CDNS_SPI_TXD, txw);
> > > +		xspi->txbuf = (u8 *)xspi->txbuf + xspi->n_bytes;
> > > +	}
> 
> > cdns_spi_write(xspi, CDNS_SPI_TXD, txw) needs to be called regardless of xspi->txbuf.
> > Otherwise, there will be no clock for the read operation to work.
> > This is a bug I am seeing on a Zedboard running on 6.19
> 
> So the device needs to be flagged as SPI_CONTROLLER_MUST_TX?

yes, It works if

ctlr->flags = SPI_CONTROLLER_MUST_TX;

is added to the probe function. At least for my case handling with "xlnx,zynq-spi-r1p6"

kind regards,

Rodrigo Alencar