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Message-ID: <36a664b1-666d-4fc4-90d9-35b42e56973d@linaro.org>
Date: Fri, 26 Jan 2024 07:56:52 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Sam Protsenko <semen.protsenko@...aro.org>
Cc: broonie@...nel.org, andi.shyti@...nel.org, arnd@...db.de,
robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
alim.akhtar@...sung.com, linux-spi@...r.kernel.org,
linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-arch@...r.kernel.org, andre.draszik@...aro.org,
peter.griffin@...aro.org, kernel-team@...roid.com, willmcvicker@...gle.com
Subject: Re: [PATCH v2 16/28] spi: s3c64xx: simplify s3c64xx_wait_for_pio()
On 1/25/24 20:43, Sam Protsenko wrote:
> On Thu, Jan 25, 2024 at 8:50 AM Tudor Ambarus <tudor.ambarus@...aro.org> wrote:
>>
>> s3c64xx_spi_transfer_one() makes sure that for PIO the xfer->len is
>> always smaller than the fifo size. Since we can't receive more that the
>> FIFO size, droop the loop handling, the code becomes less misleading.
>
> Drop (spelling)?
oh yeah, thanks.
>
> For the patch: how exactly it was tested to make sure there is no regression?
no regression testing for the entire patch set, I have just a gs101 on
my hands.
However, we shouldn't refrain ourselves on improving things when we
think they're straight forward and they worth it. In this particular
case, for PIO, s3c64xx_spi_transfer_one() does:
xfer->len = fifo_len - 1;
then in s3c64xx_enable_datapath() we write xfer->len and then in
s3c64xx_wait_for_pio() we code did the following:
loops = xfer->len / FIFO_DEPTH(sdd);
loops is always zero, this is bogus and we shall remove it.
>>
>> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
>> ---
>> drivers/spi/spi-s3c64xx.c | 75 +++++++++------------------------------
>> 1 file changed, 17 insertions(+), 58 deletions(-)
>>
>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> index d2dd28ff00c6..00a0878aeb80 100644
>> --- a/drivers/spi/spi-s3c64xx.c
>> +++ b/drivers/spi/spi-s3c64xx.c
>> @@ -485,26 +485,6 @@ static int s3c64xx_enable_datapath(struct s3c64xx_spi_driver_data *sdd,
>> return 0;
>> }
>>
>> -static u32 s3c64xx_spi_wait_for_timeout(struct s3c64xx_spi_driver_data *sdd,
>> - int timeout_ms)
>> -{
>> - void __iomem *regs = sdd->regs;
>> - unsigned long val = 1;
>> - u32 status;
>> - u32 max_fifo = FIFO_DEPTH(sdd);
>> -
>> - if (timeout_ms)
>> - val = msecs_to_loops(timeout_ms);
>> -
>> - do {
>> - status = readl(regs + S3C64XX_SPI_STATUS);
>> - } while (FIELD_GET(S3C64XX_SPI_ST_RX_FIFO_LVL, status) < max_fifo &&
>> - --val);
>> -
>> - /* return the actual received data length */
>> - return FIELD_GET(S3C64XX_SPI_ST_RX_FIFO_LVL, status);
>> -}
>> -
>> static int s3c64xx_wait_for_dma(struct s3c64xx_spi_driver_data *sdd,
>> struct spi_transfer *xfer)
>> {
>> @@ -553,13 +533,11 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
>> struct spi_transfer *xfer, bool use_irq)
>> {
>> void __iomem *regs = sdd->regs;
>> + u8 *buf = xfer->rx_buf;
>> + unsigned long time_us;
>> unsigned long val;
>> - u32 status;
>> - int loops;
>> - u32 cpy_len;
>> - u8 *buf;
>> + u32 status, len;
>> int ms;
>> - unsigned long time_us;
>>
>> /* microsecs to xfer 'len' bytes @ 'cur_speed' */
>> time_us = (xfer->len * 8 * 1000 * 1000) / sdd->cur_speed;
>> @@ -582,48 +560,29 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
>> status = readl(regs + S3C64XX_SPI_STATUS);
>> } while (FIELD_GET(S3C64XX_SPI_ST_RX_FIFO_LVL, status) < xfer->len &&
>> --val);
>> -
>> if (!val)
>> return -EIO;
>>
>> /* If it was only Tx */
>> - if (!xfer->rx_buf) {
>> + if (!buf) {
>> sdd->state &= ~TXBUSY;
>> return 0;
>> }
>>
>> - /*
>> - * If the receive length is bigger than the controller fifo
>> - * size, calculate the loops and read the fifo as many times.
>> - * loops = length / max fifo size (calculated by using the
>> - * fifo mask).
>> - * For any size less than the fifo size the below code is
>> - * executed atleast once.
>> - */
>> - loops = xfer->len / FIFO_DEPTH(sdd);
>> - buf = xfer->rx_buf;
>> - do {
>> - /* wait for data to be received in the fifo */
>> - cpy_len = s3c64xx_spi_wait_for_timeout(sdd,
>> - (loops ? ms : 0));
>> -
>> - switch (sdd->cur_bpw) {
>> - case 32:
>> - ioread32_rep(regs + S3C64XX_SPI_RX_DATA,
>> - buf, cpy_len / 4);
>> - break;
>> - case 16:
>> - ioread16_rep(regs + S3C64XX_SPI_RX_DATA,
>> - buf, cpy_len / 2);
>> - break;
>> - default:
>> - ioread8_rep(regs + S3C64XX_SPI_RX_DATA,
>> - buf, cpy_len);
>> - break;
>> - }
>> + len = FIELD_GET(S3C64XX_SPI_ST_RX_FIFO_LVL, status);
>> +
>> + switch (sdd->cur_bpw) {
>> + case 32:
>> + ioread32_rep(regs + S3C64XX_SPI_RX_DATA, buf, len / 4);
>> + break;
>> + case 16:
>> + ioread16_rep(regs + S3C64XX_SPI_RX_DATA, buf, len / 2);
>> + break;
>> + default:
>> + ioread8_rep(regs + S3C64XX_SPI_RX_DATA, buf, len);
>> + break;
>> + }
>>
>> - buf = buf + cpy_len;
>> - } while (loops--);
>> sdd->state &= ~RXBUSY;
>>
>> return 0;
>> --
>> 2.43.0.429.g432eaa2c6b-goog
>>
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