Re: [PATCH 3/3] spi: spi-geni-qcom: Get rid of most overhead in prepare_message()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On 7/2/2020 6:15 AM, Douglas Anderson wrote:
There's a bunch of overhead in spi-geni-qcom's prepare_message.  Get
rid of it.  Before this change spi_geni_prepare_message() took around
14.5 us.  After this change, spi_geni_prepare_message() takes about
1.75 us (as measured by ftrace).

What's here:
* We're always in FIFO mode, so no need to call it for every transfer.
   This avoids a whole ton of readl/writel calls.
* We don't need to write a whole pile of config registers if the mode
   isn't changing.  Cache the last mode and only do the work if needed.
* For several registers we were trying to do read/modify/write, but
   there was no reason.  The registers only have one thing in them, so
   just write them.

Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---

  drivers/spi/spi-geni-qcom.c | 54 +++++++++++++++++--------------------
  1 file changed, 24 insertions(+), 30 deletions(-)

diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
index f51279608fc7..97fac5ea6afd 100644
--- a/drivers/spi/spi-geni-qcom.c
+++ b/drivers/spi/spi-geni-qcom.c
@@ -77,6 +77,7 @@ struct spi_geni_master {
  	u32 tx_fifo_depth;
  	u32 fifo_width_bits;
  	u32 tx_wm;
+	u32 last_mode;
  	unsigned long cur_speed_hz;
  	unsigned int cur_bits_per_word;
  	unsigned int tx_rem_bytes;
@@ -177,8 +178,6 @@ static void spi_setup_word_len(struct spi_geni_master *mas, u16 mode,
  	struct geni_se *se = &mas->se;
  	u32 word_len;
- word_len = readl(se->base + SE_SPI_WORD_LEN);
-
  	/*
  	 * If bits_per_word isn't a byte aligned value, set the packing to be
  	 * 1 SPI word per FIFO word.
@@ -187,10 +186,9 @@ static void spi_setup_word_len(struct spi_geni_master *mas, u16 mode,
  		pack_words = mas->fifo_width_bits / bits_per_word;
  	else
  		pack_words = 1;
-	word_len &= ~WORD_LEN_MSK;
-	word_len |= ((bits_per_word - MIN_WORD_LEN) & WORD_LEN_MSK);
  	geni_se_config_packing(&mas->se, bits_per_word, pack_words, msb_first,
  								true, true);
+	word_len = (bits_per_word - MIN_WORD_LEN) & WORD_LEN_MSK;
  	writel(word_len, se->base + SE_SPI_WORD_LEN);
  }
@@ -238,38 +236,34 @@ static int setup_fifo_params(struct spi_device *spi_slv,
  {
  	struct spi_geni_master *mas = spi_master_get_devdata(spi);
  	struct geni_se *se = &mas->se;
-	u32 loopback_cfg, cpol, cpha, demux_output_inv;
+	u32 loopback_cfg = 0, cpol = 0, cpha = 0, demux_output_inv = 0;
  	u32 demux_sel;
- loopback_cfg = readl(se->base + SE_SPI_LOOPBACK);
-	cpol = readl(se->base + SE_SPI_CPOL);
-	cpha = readl(se->base + SE_SPI_CPHA);
-	demux_output_inv = 0;
-	loopback_cfg &= ~LOOPBACK_MSK;
-	cpol &= ~CPOL;
-	cpha &= ~CPHA;
+	if (mas->last_mode != spi_slv->mode) {
+		if (spi_slv->mode & SPI_LOOP)
+			loopback_cfg = LOOPBACK_ENABLE;
- if (spi_slv->mode & SPI_LOOP)
-		loopback_cfg |= LOOPBACK_ENABLE;
+		if (spi_slv->mode & SPI_CPOL)
+			cpol = CPOL;
- if (spi_slv->mode & SPI_CPOL)
-		cpol |= CPOL;
+		if (spi_slv->mode & SPI_CPHA)
+			cpha = CPHA;
- if (spi_slv->mode & SPI_CPHA)
-		cpha |= CPHA;
+		if (spi_slv->mode & SPI_CS_HIGH)
+			demux_output_inv = BIT(spi_slv->chip_select);
- if (spi_slv->mode & SPI_CS_HIGH)
-		demux_output_inv = BIT(spi_slv->chip_select);
+		demux_sel = spi_slv->chip_select;
+		mas->cur_bits_per_word = spi_slv->bits_per_word;
- demux_sel = spi_slv->chip_select;
-	mas->cur_bits_per_word = spi_slv->bits_per_word;
+		spi_setup_word_len(mas, spi_slv->mode, spi_slv->bits_per_word);
+		writel(loopback_cfg, se->base + SE_SPI_LOOPBACK);
+		writel(demux_sel, se->base + SE_SPI_DEMUX_SEL);
+		writel(cpha, se->base + SE_SPI_CPHA);
+		writel(cpol, se->base + SE_SPI_CPOL);
+		writel(demux_output_inv, se->base + SE_SPI_DEMUX_OUTPUT_INV);
- spi_setup_word_len(mas, spi_slv->mode, spi_slv->bits_per_word);
-	writel(loopback_cfg, se->base + SE_SPI_LOOPBACK);
-	writel(demux_sel, se->base + SE_SPI_DEMUX_SEL);
-	writel(cpha, se->base + SE_SPI_CPHA);
-	writel(cpol, se->base + SE_SPI_CPOL);
-	writel(demux_output_inv, se->base + SE_SPI_DEMUX_OUTPUT_INV);
+		mas->last_mode = spi_slv->mode;
+	}
return geni_spi_set_clock_and_bw(mas, spi_slv->max_speed_hz);
  }

Yeah looks good to me, the default/reset value of these registers are 0 we don't have to preserve any bits here.

We can directly update the register with required value.

Reviewed-by: Akash Asthana <akashast@xxxxxxxxxxxxxx>

--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,\na Linux Foundation Collaborative Project




[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [Linux for Sparc]     [IETF Annouce]     [Security]     [Bugtraq]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux