| Message ID | 20180717143154.28241-3-maxime.chevallier@bootlin.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Jul 17, 2018 at 04:31:51PM +0200, Maxime Chevallier wrote: > The dynamic bursts mode allows to group together multiple words into a > single burst. To do so, it's necessary that words can be packed into the > 32-bits FIFO entries, so we can't allow using this mode with bit_per_words > different to 8, 16 or 32. > > This prevents shitfing out extra clock ticks for transfers with s/shitfing/shifting/ > bit_per_word values not aligned on 8 bits. > > With that , we are sure that only the correct number of bits is > shifted out at each transfer, so we don't need to mask out the remaining > parts of the words. > > Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com> Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de> Sascha > --- > drivers/spi/spi-imx.c | 23 +++++++++-------------- > 1 file changed, 9 insertions(+), 14 deletions(-) > > diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c > index d75153c995af..ecafbda5ec94 100644 > --- a/drivers/spi/spi-imx.c > +++ b/drivers/spi/spi-imx.c > @@ -95,7 +95,6 @@ struct spi_imx_data { > const void *tx_buf; > unsigned int txfifo; /* number of words pushed in tx FIFO */ > unsigned int dynamic_burst, read_u32; > - unsigned int word_mask; > > /* Slave mode */ > bool slave_mode; > @@ -291,7 +290,6 @@ static void spi_imx_buf_rx_swap_u32(struct spi_imx_data *spi_imx) > else if (bytes_per_word == 2) > val = (val << 16) | (val >> 16); > #endif > - val &= spi_imx->word_mask; > *(u32 *)spi_imx->rx_buf = val; > spi_imx->rx_buf += sizeof(u32); > } > @@ -322,7 +320,6 @@ static void spi_imx_buf_tx_swap_u32(struct spi_imx_data *spi_imx) > > if (spi_imx->tx_buf) { > val = *(u32 *)spi_imx->tx_buf; > - val &= spi_imx->word_mask; > spi_imx->tx_buf += sizeof(u32); > } > > @@ -1102,25 +1099,23 @@ static int spi_imx_setupxfer(struct spi_device *spi, > spi_imx->bits_per_word = t->bits_per_word; > spi_imx->speed_hz = t->speed_hz; > > - /* Initialize the functions for transfer */ > - if (spi_imx->devtype_data->dynamic_burst && !spi_imx->slave_mode) { > - u32 mask; > + /* > + * Initialize the functions for transfer. To transfer non byte-aligned > + * words, we have to use multiple word-size bursts, we can't use > + * dynamic_burst in that case. > + */ > + if (spi_imx->devtype_data->dynamic_burst && !spi_imx->slave_mode && > + (spi_imx->bits_per_word == 8 || > + spi_imx->bits_per_word == 16 || > + spi_imx->bits_per_word == 32)) { > > spi_imx->read_u32 = 1; > > - mask = (1 << spi_imx->bits_per_word) - 1; > spi_imx->rx = spi_imx_buf_rx_swap; > spi_imx->tx = spi_imx_buf_tx_swap; > spi_imx->dynamic_burst = 1; > spi_imx->remainder = t->len; > > - if (spi_imx->bits_per_word <= 8) > - spi_imx->word_mask = mask << 24 | mask << 16 > - | mask << 8 | mask; > - else if (spi_imx->bits_per_word <= 16) > - spi_imx->word_mask = mask << 16 | mask; > - else > - spi_imx->word_mask = mask; > } else { > if (spi_imx->bits_per_word <= 8) { > spi_imx->rx = spi_imx_buf_rx_u8; > -- > 2.11.0 > >
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index d75153c995af..ecafbda5ec94 100644 --- a/drivers/spi/spi-imx.c +++ b/drivers/spi/spi-imx.c @@ -95,7 +95,6 @@ struct spi_imx_data { const void *tx_buf; unsigned int txfifo; /* number of words pushed in tx FIFO */ unsigned int dynamic_burst, read_u32; - unsigned int word_mask; /* Slave mode */ bool slave_mode; @@ -291,7 +290,6 @@ static void spi_imx_buf_rx_swap_u32(struct spi_imx_data *spi_imx) else if (bytes_per_word == 2) val = (val << 16) | (val >> 16); #endif - val &= spi_imx->word_mask; *(u32 *)spi_imx->rx_buf = val; spi_imx->rx_buf += sizeof(u32); } @@ -322,7 +320,6 @@ static void spi_imx_buf_tx_swap_u32(struct spi_imx_data *spi_imx) if (spi_imx->tx_buf) { val = *(u32 *)spi_imx->tx_buf; - val &= spi_imx->word_mask; spi_imx->tx_buf += sizeof(u32); } @@ -1102,25 +1099,23 @@ static int spi_imx_setupxfer(struct spi_device *spi, spi_imx->bits_per_word = t->bits_per_word; spi_imx->speed_hz = t->speed_hz; - /* Initialize the functions for transfer */ - if (spi_imx->devtype_data->dynamic_burst && !spi_imx->slave_mode) { - u32 mask; + /* + * Initialize the functions for transfer. To transfer non byte-aligned + * words, we have to use multiple word-size bursts, we can't use + * dynamic_burst in that case. + */ + if (spi_imx->devtype_data->dynamic_burst && !spi_imx->slave_mode && + (spi_imx->bits_per_word == 8 || + spi_imx->bits_per_word == 16 || + spi_imx->bits_per_word == 32)) { spi_imx->read_u32 = 1; - mask = (1 << spi_imx->bits_per_word) - 1; spi_imx->rx = spi_imx_buf_rx_swap; spi_imx->tx = spi_imx_buf_tx_swap; spi_imx->dynamic_burst = 1; spi_imx->remainder = t->len; - if (spi_imx->bits_per_word <= 8) - spi_imx->word_mask = mask << 24 | mask << 16 - | mask << 8 | mask; - else if (spi_imx->bits_per_word <= 16) - spi_imx->word_mask = mask << 16 | mask; - else - spi_imx->word_mask = mask; } else { if (spi_imx->bits_per_word <= 8) { spi_imx->rx = spi_imx_buf_rx_u8;
The dynamic bursts mode allows to group together multiple words into a single burst. To do so, it's necessary that words can be packed into the 32-bits FIFO entries, so we can't allow using this mode with bit_per_words different to 8, 16 or 32. This prevents shitfing out extra clock ticks for transfers with bit_per_word values not aligned on 8 bits. With that , we are sure that only the correct number of bits is shifted out at each transfer, so we don't need to mask out the remaining parts of the words. Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com> --- drivers/spi/spi-imx.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-)