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| author | Geert Uytterhoeven <geert+renesas@glider.be> | 2020-06-08 11:59:34 +0200 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2020-06-09 12:26:33 +0100 |
| commit | e0fe70051f12c25c4afb04cb10ca8648c6e761cf (patch) | |
| tree | 48cad74b6a0d144e979e9682a0f30fa0baf459a6 | |
| parent | 9ec8ade812240f3ef553b5e8bfc74deec3f14339 (diff) | |
| download | lwn-e0fe70051f12c25c4afb04cb10ca8648c6e761cf.tar.gz lwn-e0fe70051f12c25c4afb04cb10ca8648c6e761cf.zip | |
spi: rspi: Use requested instead of maximum bit rate
Currently, the RSPI driver always tries to use the maximum configured
bit rate for communicating with a slave device, even if the transfer(s)
in the current message specify a lower rate.
Use the mininum rate specified in the message instead.
Rename rspi_data.max_speed_hz accordingly.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200608095940.30516-3-geert+renesas@glider.be
Signed-off-by: Mark Brown <broonie@kernel.org>
| -rw-r--r-- | drivers/spi/spi-rspi.c | 28 |
1 files changed, 21 insertions, 7 deletions
diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c index 06192c9ea813..cbc2387d450c 100644 --- a/drivers/spi/spi-rspi.c +++ b/drivers/spi/spi-rspi.c @@ -179,7 +179,7 @@ struct rspi_data { void __iomem *addr; - u32 max_speed_hz; + u32 speed_hz; struct spi_controller *ctlr; struct platform_device *pdev; wait_queue_head_t wait; @@ -258,8 +258,7 @@ static int rspi_set_config_register(struct rspi_data *rspi, int access_size) rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR); /* Sets transfer bit rate */ - spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), - 2 * rspi->max_speed_hz) - 1; + spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->speed_hz) - 1; rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR); /* Disable dummy transmission, set 16-bit word access, 1 frame */ @@ -299,14 +298,14 @@ static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size) clksrc = clk_get_rate(rspi->clk); while (div < 3) { - if (rspi->max_speed_hz >= clksrc/4) /* 4=(CLK/2)/2 */ + if (rspi->speed_hz >= clksrc/4) /* 4=(CLK/2)/2 */ break; div++; clksrc /= 2; } /* Sets transfer bit rate */ - spbr = DIV_ROUND_UP(clksrc, 2 * rspi->max_speed_hz) - 1; + spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz) - 1; rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR); rspi->spcmd |= div << 2; @@ -341,7 +340,7 @@ static int qspi_set_config_register(struct rspi_data *rspi, int access_size) rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR); /* Sets transfer bit rate */ - spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->max_speed_hz); + spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->speed_hz); rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR); /* Disable dummy transmission, set byte access */ @@ -949,9 +948,24 @@ static int rspi_prepare_message(struct spi_controller *ctlr, { struct rspi_data *rspi = spi_controller_get_devdata(ctlr); struct spi_device *spi = msg->spi; + const struct spi_transfer *xfer; int ret; - rspi->max_speed_hz = spi->max_speed_hz; + /* + * As the Bit Rate Register must not be changed while the device is + * active, all transfers in a message must use the same bit rate. + * In theory, the sequencer could be enabled, and each Command Register + * could divide the base bit rate by a different value. + * However, most RSPI variants do not have Transfer Data Length + * Multiplier Setting Registers, so each sequence step would be limited + * to a single word, making this feature unsuitable for large + * transfers, which would gain most from it. + */ + rspi->speed_hz = spi->max_speed_hz; + list_for_each_entry(xfer, &msg->transfers, transfer_list) { + if (xfer->speed_hz < rspi->speed_hz) + rspi->speed_hz = xfer->speed_hz; + } rspi->spcmd = SPCMD_SSLKP; if (spi->mode & SPI_CPOL) |