[PATCH 0/9] spi: spi-sun6i: One fix and some improvements

[PATCH 0/9] spi: spi-sun6i: One fix and some improvements

[Marc Kleine-Budde]

Hello,

this series first fixes the calculation of the clock rate. The driver will
round up to the nearest clock rate instead of rounding down. Resulting in SPI
devices accessed with a too high SPI clock.

The remaining patches improve the performance of the driver. The changes range
from micro-optimizations like reducing MMIO writes to the controller to
reducing the number of needed interrupts in some use cases.

regards,
Marc

[PATCH 1/9] spi: spi-sun6i: sun6i_spi_transfer_one(): fix setting of clock rate

[Marc Kleine-Budde]

A SPI transfer defines the _maximum_ speed of the SPI transfer. However the
driver doesn't take into account that the clock divider is always rounded down
(due to integer arithmetics). This results in a too high clock rate for the SPI
transfer.

E.g.: with a mclk_rate of 24 MHz and a SPI transfer speed of 10 MHz, the
original code calculates a reg of "0", which results in a effective divider of
"2" and a 12 MHz clock for the SPI transfer.

This patch fixes the issue by using DIV_ROUND_UP() instead of a plain
integer division.

While there simplify the divider calculation for the CDR1 case, use
order_base_2() instead of two ilog2() calculations.

Fixes: 3558fe900e8a ("spi: sunxi: Add Allwinner A31 SPI controller driver")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index ecea15534c42..fa11cc0e809b 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -198,7 +198,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 				  struct spi_transfer *tfr)
 {
 	struct sun6i_spi *sspi = spi_master_get_devdata(master);
-	unsigned int mclk_rate, div, timeout;
+	unsigned int mclk_rate, div, div_cdr1, div_cdr2, timeout;
 	unsigned int start, end, tx_time;
 	unsigned int trig_level;
 	unsigned int tx_len = 0;
@@ -287,14 +287,12 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 	 * First try CDR2, and if we can't reach the expected
 	 * frequency, fall back to CDR1.
 	 */
-	div = mclk_rate / (2 * tfr->speed_hz);
-	if (div <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) {
-		if (div > 0)
-			div--;
-
-		reg = SUN6I_CLK_CTL_CDR2(div) | SUN6I_CLK_CTL_DRS;
+	div_cdr1 = DIV_ROUND_UP(mclk_rate, tfr->speed_hz);
+	div_cdr2 = DIV_ROUND_UP(div_cdr1, 2);
+	if (div_cdr2 <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) {
+		reg = SUN6I_CLK_CTL_CDR2(div_cdr2 - 1) | SUN6I_CLK_CTL_DRS;
 	} else {
-		div = ilog2(mclk_rate) - ilog2(tfr->speed_hz);
+		div = min(SUN6I_CLK_CTL_CDR1_MASK, order_base_2(div_cdr1));
 		reg = SUN6I_CLK_CTL_CDR1(div);
 	}
 
-- 
2.27.0

[PATCH 2/9] spi: spi-sun6i: sun6i_spi_transfer_one(): report effectivly used speed_hz of transfer

[Marc Kleine-Budde]

This patch implementes the reporting of the effectivly used speed_hz for the
transfer by setting tfr->effective_speed_hz.

See the following patch, which adds this feature to the SPI core for more
information:

    5d7e2b5ed585 spi: core: allow reporting the effectivly used speed_hz for a transfer

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index fa11cc0e809b..64b4d8077010 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -291,9 +291,11 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 	div_cdr2 = DIV_ROUND_UP(div_cdr1, 2);
 	if (div_cdr2 <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) {
 		reg = SUN6I_CLK_CTL_CDR2(div_cdr2 - 1) | SUN6I_CLK_CTL_DRS;
+		tfr->effective_speed_hz = mclk_rate / (2 * div_cdr2);
 	} else {
 		div = min(SUN6I_CLK_CTL_CDR1_MASK, order_base_2(div_cdr1));
 		reg = SUN6I_CLK_CTL_CDR1(div);
+		tfr->effective_speed_hz = mclk_rate / (1 << div);
 	}
 
 	sun6i_spi_write(sspi, SUN6I_CLK_CTL_REG, reg);
-- 
2.27.0

[PATCH 3/9] spi: spi-sun6i: sun6i_spi_transfer_one(): remove useless goto

[Marc Kleine-Budde]

This patch removes an useless goto at the end of
sun6i_spi_transfer_one().

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index 64b4d8077010..955be8921c45 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -335,10 +335,8 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 			 dev_name(&spi->dev), tfr->len, tfr->speed_hz,
 			 jiffies_to_msecs(end - start), tx_time);
 		ret = -ETIMEDOUT;
-		goto out;
 	}
 
-out:
 	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, 0);
 
 	return ret;
-- 
2.27.0

[PATCH 4/9] spi: spi-sun6i: sun6i_spi_transfer_one(): remove not needed masking of transfer length

[Marc Kleine-Budde]

In sun6i_spi_transfer_one() the driver ensures that the length of the transfer
is smaller or equal to SUN6I_MAX_XFER_SIZE. This means the masking of the
length to SUN6I_MAX_XFER_SIZE can be skipped when writing the transfer length
into the registers.

This patch removes the useless masking of the transfer length to
SUN6I_MAX_XFER_SIZE.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index 955be8921c45..882492774986 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -73,13 +73,10 @@
 #define SUN6I_MAX_XFER_SIZE		0xffffff
 
 #define SUN6I_BURST_CNT_REG		0x30
-#define SUN6I_BURST_CNT(cnt)			((cnt) & SUN6I_MAX_XFER_SIZE)
 
 #define SUN6I_XMIT_CNT_REG		0x34
-#define SUN6I_XMIT_CNT(cnt)			((cnt) & SUN6I_MAX_XFER_SIZE)
 
 #define SUN6I_BURST_CTL_CNT_REG		0x38
-#define SUN6I_BURST_CTL_CNT_STC(cnt)		((cnt) & SUN6I_MAX_XFER_SIZE)
 
 #define SUN6I_TXDATA_REG		0x200
 #define SUN6I_RXDATA_REG		0x300
@@ -305,10 +302,9 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 		tx_len = tfr->len;
 
 	/* Setup the counters */
-	sun6i_spi_write(sspi, SUN6I_BURST_CNT_REG, SUN6I_BURST_CNT(tfr->len));
-	sun6i_spi_write(sspi, SUN6I_XMIT_CNT_REG, SUN6I_XMIT_CNT(tx_len));
-	sun6i_spi_write(sspi, SUN6I_BURST_CTL_CNT_REG,
-			SUN6I_BURST_CTL_CNT_STC(tx_len));
+	sun6i_spi_write(sspi, SUN6I_BURST_CNT_REG, tfr->len);
+	sun6i_spi_write(sspi, SUN6I_XMIT_CNT_REG, tx_len);
+	sun6i_spi_write(sspi, SUN6I_BURST_CTL_CNT_REG, tx_len);
 
 	/* Fill the TX FIFO */
 	sun6i_spi_fill_fifo(sspi, sspi->fifo_depth);
-- 
2.27.0

[PATCH 5/9] spi: spi-sun6i: sun6i_spi_drain_fifo(): introduce sun6i_spi_get_rx_fifo_count() and make use of it

[Marc Kleine-Budde]

This patch introduces the function sun6i_spi_get_rx_fifo_count(), similar to
the existing sun6i_spi_get_tx_fifo_count(), to make the sun6i_spi_drain_fifo()
function a bit easier to read.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index 882492774986..f70d14229483 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -106,6 +106,15 @@ static inline void sun6i_spi_write(struct sun6i_spi *sspi, u32 reg, u32 value)
 	writel(value, sspi->base_addr + reg);
 }
 
+static inline u32 sun6i_spi_get_rx_fifo_count(struct sun6i_spi *sspi)
+{
+	u32 reg = sun6i_spi_read(sspi, SUN6I_FIFO_STA_REG);
+
+	reg >>= SUN6I_FIFO_STA_RF_CNT_BITS;
+
+	return reg & SUN6I_FIFO_STA_RF_CNT_MASK;
+}
+
 static inline u32 sun6i_spi_get_tx_fifo_count(struct sun6i_spi *sspi)
 {
 	u32 reg = sun6i_spi_read(sspi, SUN6I_FIFO_STA_REG);
@@ -133,13 +142,11 @@ static inline void sun6i_spi_disable_interrupt(struct sun6i_spi *sspi, u32 mask)
 
 static inline void sun6i_spi_drain_fifo(struct sun6i_spi *sspi, int len)
 {
-	u32 reg, cnt;
+	u32 cnt;
 	u8 byte;
 
 	/* See how much data is available */
-	reg = sun6i_spi_read(sspi, SUN6I_FIFO_STA_REG);
-	reg &= SUN6I_FIFO_STA_RF_CNT_MASK;
-	cnt = reg >> SUN6I_FIFO_STA_RF_CNT_BITS;
+	cnt = sun6i_spi_get_rx_fifo_count(sspi);
 
 	if (len > cnt)
 		len = cnt;
-- 
2.27.0

Re: [PATCH 5/9] spi: spi-sun6i: sun6i_spi_drain_fifo(): introduce sun6i_spi_get_rx_fifo_count() and make use of it

[Maxime Ripard]

On Mon, Jul 06, 2020 at 09:17:57AM +0200, Marc Kleine-Budde wrote:
> This patch introduces the function sun6i_spi_get_rx_fifo_count(), similar to
> the existing sun6i_spi_get_tx_fifo_count(), to make the sun6i_spi_drain_fifo()
> function a bit easier to read.
> 
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> ---
>  drivers/spi/spi-sun6i.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
> index 882492774986..f70d14229483 100644
> --- a/drivers/spi/spi-sun6i.c
> +++ b/drivers/spi/spi-sun6i.c
> @@ -106,6 +106,15 @@ static inline void sun6i_spi_write(struct sun6i_spi *sspi, u32 reg, u32 value)
>  	writel(value, sspi->base_addr + reg);
>  }
>  
> +static inline u32 sun6i_spi_get_rx_fifo_count(struct sun6i_spi *sspi)
> +{
> +	u32 reg = sun6i_spi_read(sspi, SUN6I_FIFO_STA_REG);
> +
> +	reg >>= SUN6I_FIFO_STA_RF_CNT_BITS;
> +
> +	return reg & SUN6I_FIFO_STA_RF_CNT_MASK;
> +}
> +

I guess we could just use FIELD_GET here?

Looks good otherwise, thanks!
Maxime

Re: [PATCH 5/9] spi: spi-sun6i: sun6i_spi_drain_fifo(): introduce sun6i_spi_get_rx_fifo_count() and make use of it

[Marc Kleine-Budde]

On 7/6/20 2:36 PM, Maxime Ripard wrote:
> On Mon, Jul 06, 2020 at 09:17:57AM +0200, Marc Kleine-Budde wrote:
>> This patch introduces the function sun6i_spi_get_rx_fifo_count(), similar to
>> the existing sun6i_spi_get_tx_fifo_count(), to make the sun6i_spi_drain_fifo()
>> function a bit easier to read.
>>
>> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
>> ---
>>  drivers/spi/spi-sun6i.c | 15 +++++++++++----
>>  1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
>> index 882492774986..f70d14229483 100644
>> --- a/drivers/spi/spi-sun6i.c
>> +++ b/drivers/spi/spi-sun6i.c
>> @@ -106,6 +106,15 @@ static inline void sun6i_spi_write(struct sun6i_spi *sspi, u32 reg, u32 value)
>>  	writel(value, sspi->base_addr + reg);
>>  }
>>  
>> +static inline u32 sun6i_spi_get_rx_fifo_count(struct sun6i_spi *sspi)
>> +{
>> +	u32 reg = sun6i_spi_read(sspi, SUN6I_FIFO_STA_REG);
>> +
>> +	reg >>= SUN6I_FIFO_STA_RF_CNT_BITS;
>> +
>> +	return reg & SUN6I_FIFO_STA_RF_CNT_MASK;
>> +}
>> +
> 
> I guess we could just use FIELD_GET here?
> 
> Looks good otherwise, thanks!

Will change in v2.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

[PATCH 6/9] spi: spi-sun6i: sun6i_spi_drain_fifo(): remove not needed length argument

[Marc Kleine-Budde]

The function sun6i_spi_drain_fifo() is called with a length argument of
"sspi->fifo_depth" and "SUN6I_FIFO_DEPTH".

The driver reads the number of available bytes to read from the FIFO from the
hardware and uses the length argument to limit this value. This is not needed
as the FIFO can contain only the fifo depth number of bytes.

This patch removes the length argument and check.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index f70d14229483..aa0daca0cbbf 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -140,16 +140,13 @@ static inline void sun6i_spi_disable_interrupt(struct sun6i_spi *sspi, u32 mask)
 	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, reg);
 }
 
-static inline void sun6i_spi_drain_fifo(struct sun6i_spi *sspi, int len)
+static inline void sun6i_spi_drain_fifo(struct sun6i_spi *sspi)
 {
-	u32 cnt;
+	u32 len;
 	u8 byte;
 
 	/* See how much data is available */
-	cnt = sun6i_spi_get_rx_fifo_count(sspi);
-
-	if (len > cnt)
-		len = cnt;
+	len = sun6i_spi_get_rx_fifo_count(sspi);
 
 	while (len--) {
 		byte = readb(sspi->base_addr + SUN6I_RXDATA_REG);
@@ -353,14 +350,14 @@ static irqreturn_t sun6i_spi_handler(int irq, void *dev_id)
 	/* Transfer complete */
 	if (status & SUN6I_INT_CTL_TC) {
 		sun6i_spi_write(sspi, SUN6I_INT_STA_REG, SUN6I_INT_CTL_TC);
-		sun6i_spi_drain_fifo(sspi, sspi->fifo_depth);
+		sun6i_spi_drain_fifo(sspi);
 		complete(&sspi->done);
 		return IRQ_HANDLED;
 	}
 
 	/* Receive FIFO 3/4 full */
 	if (status & SUN6I_INT_CTL_RF_RDY) {
-		sun6i_spi_drain_fifo(sspi, SUN6I_FIFO_DEPTH);
+		sun6i_spi_drain_fifo(sspi);
 		/* Only clear the interrupt _after_ draining the FIFO */
 		sun6i_spi_write(sspi, SUN6I_INT_STA_REG, SUN6I_INT_CTL_RF_RDY);
 		return IRQ_HANDLED;
-- 
2.27.0

[PATCH 7/9] spi: spi-sun6i: sun6i_spi_fill_fifo(): remove not needed length argument

[Marc Kleine-Budde]

The function sun6i_spi_fill_fifo() is called with a length argument of
"sspi->fifo_depth" and "SUN6I_FIFO_DEPTH".

The driver reads the number of free bytes in the FIFO from the hardware and
uses the length argument to limit this value. This is not needed as the number
of free bytes in the FIFO is always less or equal the depth of the FIFO.

This patch removes the length argument and check.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index aa0daca0cbbf..da56e9bc2cc3 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -155,15 +155,16 @@ static inline void sun6i_spi_drain_fifo(struct sun6i_spi *sspi)
 	}
 }
 
-static inline void sun6i_spi_fill_fifo(struct sun6i_spi *sspi, int len)
+static inline void sun6i_spi_fill_fifo(struct sun6i_spi *sspi)
 {
 	u32 cnt;
+	int len;
 	u8 byte;
 
 	/* See how much data we can fit */
 	cnt = sspi->fifo_depth - sun6i_spi_get_tx_fifo_count(sspi);
 
-	len = min3(len, (int)cnt, sspi->len);
+	len = min((int)cnt, sspi->len);
 
 	while (len--) {
 		byte = sspi->tx_buf ? *sspi->tx_buf++ : 0;
@@ -311,7 +312,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 	sun6i_spi_write(sspi, SUN6I_BURST_CTL_CNT_REG, tx_len);
 
 	/* Fill the TX FIFO */
-	sun6i_spi_fill_fifo(sspi, sspi->fifo_depth);
+	sun6i_spi_fill_fifo(sspi);
 
 	/* Enable the interrupts */
 	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, SUN6I_INT_CTL_TC);
@@ -365,7 +366,7 @@ static irqreturn_t sun6i_spi_handler(int irq, void *dev_id)
 
 	/* Transmit FIFO 3/4 empty */
 	if (status & SUN6I_INT_CTL_TF_ERQ) {
-		sun6i_spi_fill_fifo(sspi, SUN6I_FIFO_DEPTH);
+		sun6i_spi_fill_fifo(sspi);
 
 		if (!sspi->len)
 			/* nothing left to transmit */
-- 
2.27.0

[PATCH 8/9] spi: spi-sun6i: sun6i_spi_transfer_one(): collate write to Interrupt Control Register

[Marc Kleine-Budde]

In sun6i_spi_transfer_one() the Interrupt Control Register is written three
times. This patch collates the three writes into one.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index da56e9bc2cc3..21b4436a72de 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -124,14 +124,6 @@ static inline u32 sun6i_spi_get_tx_fifo_count(struct sun6i_spi *sspi)
 	return reg & SUN6I_FIFO_STA_TF_CNT_MASK;
 }
 
-static inline void sun6i_spi_enable_interrupt(struct sun6i_spi *sspi, u32 mask)
-{
-	u32 reg = sun6i_spi_read(sspi, SUN6I_INT_CTL_REG);
-
-	reg |= mask;
-	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, reg);
-}
-
 static inline void sun6i_spi_disable_interrupt(struct sun6i_spi *sspi, u32 mask)
 {
 	u32 reg = sun6i_spi_read(sspi, SUN6I_INT_CTL_REG);
@@ -315,11 +307,12 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 	sun6i_spi_fill_fifo(sspi);
 
 	/* Enable the interrupts */
-	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, SUN6I_INT_CTL_TC);
-	sun6i_spi_enable_interrupt(sspi, SUN6I_INT_CTL_TC |
-					 SUN6I_INT_CTL_RF_RDY);
+	reg = SUN6I_INT_CTL_TC | SUN6I_INT_CTL_RF_RDY;
+
 	if (tx_len > sspi->fifo_depth)
-		sun6i_spi_enable_interrupt(sspi, SUN6I_INT_CTL_TF_ERQ);
+		reg |= SUN6I_INT_CTL_TF_ERQ;
+
+	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, reg);
 
 	/* Start the transfer */
 	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
-- 
2.27.0

[PATCH 9/9] spi: spi-sun6i: sun6i_spi_transfer_one(): enable RF_RDY interrupt only if needed

[Marc Kleine-Budde]

In sun6i_spi_transfer_one() the RX FIFO Ready (SUN6I_INT_CTL_RF_RDY) is
unconditionally enabled.

A RX interrupt is only needed, if more data than fits into the FIFO is going to
be received during this transfer. As the RX-FIFO is drained during transfer
complete interrupt, enable the RX FIFO Ready interrupt only if the data doesn't
fit into the FIFO.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/spi/spi-sun6i.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index 21b4436a72de..9379ce477bc3 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -195,7 +195,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 	unsigned int mclk_rate, div, div_cdr1, div_cdr2, timeout;
 	unsigned int start, end, tx_time;
 	unsigned int trig_level;
-	unsigned int tx_len = 0;
+	unsigned int tx_len = 0, rx_len = 0;
 	int ret = 0;
 	u32 reg;
 
@@ -250,10 +250,12 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 	 * If it's a TX only transfer, we don't want to fill the RX
 	 * FIFO with bogus data
 	 */
-	if (sspi->rx_buf)
+	if (sspi->rx_buf) {
 		reg &= ~SUN6I_TFR_CTL_DHB;
-	else
+		rx_len = tfr->len;
+	} else {
 		reg |= SUN6I_TFR_CTL_DHB;
+	}
 
 	/* We want to control the chip select manually */
 	reg |= SUN6I_TFR_CTL_CS_MANUAL;
@@ -307,8 +309,10 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
 	sun6i_spi_fill_fifo(sspi);
 
 	/* Enable the interrupts */
-	reg = SUN6I_INT_CTL_TC | SUN6I_INT_CTL_RF_RDY;
+	reg = SUN6I_INT_CTL_TC;
 
+	if (rx_len > sspi->fifo_depth)
+		reg |= SUN6I_INT_CTL_RF_RDY;
 	if (tx_len > sspi->fifo_depth)
 		reg |= SUN6I_INT_CTL_TF_ERQ;
 
-- 
2.27.0

Re: [PATCH 0/9] spi: spi-sun6i: One fix and some improvements

[Maxime Ripard]

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On Mon, Jul 06, 2020 at 09:17:52AM +0200, Marc Kleine-Budde wrote:
> Hello,
> 
> this series first fixes the calculation of the clock rate. The driver will
> round up to the nearest clock rate instead of rounding down. Resulting in SPI
> devices accessed with a too high SPI clock.
> 
> The remaining patches improve the performance of the driver. The changes range
> from micro-optimizations like reducing MMIO writes to the controller to
> reducing the number of needed interrupts in some use cases.

Thanks for that work. Aside from the minor comment over FIELD_GET, the
whole series is

Acked-by: Maxime Ripard <mripard@kernel.org>

Maxime

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