linux-kernel - Re: [PATCH 06/10] staging: greybus: spilib: use 'spi_delay_to

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Message-ID: <20210309092932.kliwq6ylqlnpqekk@arch-thunder.localdomain>
Date:   Tue, 9 Mar 2021 09:29:32 +0000
From:   Rui Miguel Silva <rmfrfs@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Alexandru Ardelean <aardelean@...iqon.com>,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        greybus-dev@...ts.linaro.org, devel@...verdev.osuosl.org,
        linux-tegra@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        broonie@...nel.org, gregkh@...uxfoundation.org, elder@...nel.org,
        johan@...nel.org, vireshk@...nel.org, f.fainelli@...il.com,
        ldewangan@...dia.com, thierry.reding@...il.com,
        jonathanh@...dia.com, linux@...iqon.com
Subject: Re: [PATCH 06/10] staging: greybus: spilib: use 'spi_delay_to_ns'
 for getting xfer delay

Hi,
On Tue, Mar 09, 2021 at 09:58:09AM +0530, Viresh Kumar wrote:
> On 08-03-21, 16:54, Alexandru Ardelean wrote:
> > The intent is the removal of the 'delay_usecs' field from the
> > spi_transfer struct, as there is a 'delay' field that does the same
> > thing.
> > 
> > The spi_delay_to_ns() can be used to get the transfer delay. It works by
> > using the 'delay_usecs' field first (if it is non-zero), and finally
> > uses the 'delay' field.
> > 
> > Since the 'delay_usecs' field is going away, this change makes use of the
> > spi_delay_to_ns() function. This also means dividing the return value of
> > the function by 1000, to convert it to microseconds.
> > To prevent any potential faults when converting to microseconds and since
> > the result of spi_delay_to_ns() is int, the delay is being computed in 32
> > bits and then clamped between 0 & U16_MAX.
> > 
> > Signed-off-by: Alexandru Ardelean <aardelean@...iqon.com>
> > ---
> >  drivers/staging/greybus/spilib.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/greybus/spilib.c b/drivers/staging/greybus/spilib.c
> > index 672d540d3365..30655153df6a 100644
> > --- a/drivers/staging/greybus/spilib.c
> > +++ b/drivers/staging/greybus/spilib.c
> > @@ -245,6 +245,7 @@ static struct gb_operation *gb_spi_operation_create(struct gb_spilib *spi,
> >  	/* Fill in the transfers array */
> >  	xfer = spi->first_xfer;
> >  	while (msg->state != GB_SPI_STATE_OP_DONE) {
> > +		int xfer_delay;
> >  		if (xfer == spi->last_xfer)
> >  			xfer_len = spi->last_xfer_size;
> >  		else
> > @@ -259,7 +260,9 @@ static struct gb_operation *gb_spi_operation_create(struct gb_spilib *spi,
> >  
> >  		gb_xfer->speed_hz = cpu_to_le32(xfer->speed_hz);
> >  		gb_xfer->len = cpu_to_le32(xfer_len);
> > -		gb_xfer->delay_usecs = cpu_to_le16(xfer->delay_usecs);
> > +		xfer_delay = spi_delay_to_ns(&xfer->delay, xfer) / 1000;
> > +		xfer_delay = clamp_t(u16, xfer_delay, 0, U16_MAX);
> > +		gb_xfer->delay_usecs = cpu_to_le16(xfer_delay);
> >  		gb_xfer->cs_change = xfer->cs_change;
> >  		gb_xfer->bits_per_word = xfer->bits_per_word;
> 
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

Acked-by: Rui Miguel Silva <rmfrfs@...il.com>

------
Cheers,
     Rui