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spi: meson-spicc: add local pow2 clock ops to preserve rate between messages

Message ID 20220811134445.678446-1-narmstrong@baylibre.com (mailing list archive)
State New, archived
Headers show
Series spi: meson-spicc: add local pow2 clock ops to preserve rate between messages | expand

Commit Message

Neil Armstrong Aug. 11, 2022, 1:44 p.m. UTC 
At the end of a message, the HW gets a reset in meson_spicc_unprepare_transfer(),
this resets the SPICC_CONREG register and notably the value set by the
Common Clock Framework.

This is problematic because:
- the register value CCF can be different from the corresponding CCF cached rate
- CCF is allowed to change the clock rate whenever the HW state

This introduces:
- local pow2 clock ops checking the HW state before allowing a clock operation
- separation of legacy pow2 clock patch and new enhanced clock path
- SPICC_CONREG datarate value is now value kepts across messages

It has been checked that:
- SPICC_CONREG datarate value is kept across messages
- CCF is only allowed to change the SPICC_CONREG datarate value when busy
- SPICC_CONREG datarate value is correct for each transfer

This didn't appear before commit 3e0cf4d3fc29 ("spi: meson-spicc: add a linear clock divider support")
because we recalculated and wrote the rate for each xfer.

Fixes: 3e0cf4d3fc29 ("spi: meson-spicc: add a linear clock divider support")
Reported-by: Da Xue <da@libre.computer>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
This is a second try after [1] which was not good enough in regards to CCF.

[1] http://lore.kernel.org/r/20220809152019.461741-1-narmstrong@baylibre.com

 drivers/spi/spi-meson-spicc.c | 129 ++++++++++++++++++++++++++--------
 1 file changed, 101 insertions(+), 28 deletions(-)

Comments

Mark Brown Aug. 12, 2022, 6 p.m. UTC | #1 
On Thu, 11 Aug 2022 15:44:45 +0200, Neil Armstrong wrote:
> At the end of a message, the HW gets a reset in meson_spicc_unprepare_transfer(),
> this resets the SPICC_CONREG register and notably the value set by the
> Common Clock Framework.
> 
> This is problematic because:
> - the register value CCF can be different from the corresponding CCF cached rate
> - CCF is allowed to change the clock rate whenever the HW state
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: meson-spicc: add local pow2 clock ops to preserve rate between messages
      commit: 09992025dacd258c823f50e82db09d7ef06cdac4

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark
diff mbox series

Patch

diff --git a/drivers/spi/spi-meson-spicc.c b/drivers/spi/spi-meson-spicc.c
index 0bc7daa7afc8..e4cb52e1fe26 100644
--- a/drivers/spi/spi-meson-spicc.c
+++ b/drivers/spi/spi-meson-spicc.c
@@ -156,6 +156,7 @@  struct meson_spicc_device {
 	void __iomem			*base;
 	struct clk			*core;
 	struct clk			*pclk;
+	struct clk_divider		pow2_div;
 	struct clk			*clk;
 	struct spi_message		*message;
 	struct spi_transfer		*xfer;
@@ -168,6 +169,8 @@  struct meson_spicc_device {
 	unsigned long			xfer_remain;
 };
 
+#define pow2_clk_to_spicc(_div) container_of(_div, struct meson_spicc_device, pow2_div)
+
 static void meson_spicc_oen_enable(struct meson_spicc_device *spicc)
 {
 	u32 conf;
@@ -421,7 +424,7 @@  static int meson_spicc_prepare_message(struct spi_master *master,
 {
 	struct meson_spicc_device *spicc = spi_master_get_devdata(master);
 	struct spi_device *spi = message->spi;
-	u32 conf = 0;
+	u32 conf = readl_relaxed(spicc->base + SPICC_CONREG) & SPICC_DATARATE_MASK;
 
 	/* Store current message */
 	spicc->message = message;
@@ -458,8 +461,6 @@  static int meson_spicc_prepare_message(struct spi_master *master,
 	/* Select CS */
 	conf |= FIELD_PREP(SPICC_CS_MASK, spi->chip_select);
 
-	/* Default Clock rate core/4 */
-
 	/* Default 8bit word */
 	conf |= FIELD_PREP(SPICC_BITLENGTH_MASK, 8 - 1);
 
@@ -476,12 +477,16 @@  static int meson_spicc_prepare_message(struct spi_master *master,
 static int meson_spicc_unprepare_transfer(struct spi_master *master)
 {
 	struct meson_spicc_device *spicc = spi_master_get_devdata(master);
+	u32 conf = readl_relaxed(spicc->base + SPICC_CONREG) & SPICC_DATARATE_MASK;
 
 	/* Disable all IRQs */
 	writel(0, spicc->base + SPICC_INTREG);
 
 	device_reset_optional(&spicc->pdev->dev);
 
+	/* Set default configuration, keeping datarate field */
+	writel_relaxed(conf, spicc->base + SPICC_CONREG);
+
 	return 0;
 }
 
@@ -518,14 +523,60 @@  static void meson_spicc_cleanup(struct spi_device *spi)
  * Clk path for G12A series:
  *    pclk -> pow2 fixed div -> pow2 div -> mux -> out
  *    pclk -> enh fixed div -> enh div -> mux -> out
+ *
+ * The pow2 divider is tied to the controller HW state, and the
+ * divider is only valid when the controller is initialized.
+ *
+ * A set of clock ops is added to make sure we don't read/set this
+ * clock rate while the controller is in an unknown state.
  */
 
-static int meson_spicc_clk_init(struct meson_spicc_device *spicc)
+static unsigned long meson_spicc_pow2_recalc_rate(struct clk_hw *hw,
+						  unsigned long parent_rate)
+{
+	struct clk_divider *divider = to_clk_divider(hw);
+	struct meson_spicc_device *spicc = pow2_clk_to_spicc(divider);
+
+	if (!spicc->master->cur_msg || !spicc->master->busy)
+		return 0;
+
+	return clk_divider_ops.recalc_rate(hw, parent_rate);
+}
+
+static int meson_spicc_pow2_determine_rate(struct clk_hw *hw,
+					   struct clk_rate_request *req)
+{
+	struct clk_divider *divider = to_clk_divider(hw);
+	struct meson_spicc_device *spicc = pow2_clk_to_spicc(divider);
+
+	if (!spicc->master->cur_msg || !spicc->master->busy)
+		return -EINVAL;
+
+	return clk_divider_ops.determine_rate(hw, req);
+}
+
+static int meson_spicc_pow2_set_rate(struct clk_hw *hw, unsigned long rate,
+				     unsigned long parent_rate)
+{
+	struct clk_divider *divider = to_clk_divider(hw);
+	struct meson_spicc_device *spicc = pow2_clk_to_spicc(divider);
+
+	if (!spicc->master->cur_msg || !spicc->master->busy)
+		return -EINVAL;
+
+	return clk_divider_ops.set_rate(hw, rate, parent_rate);
+}
+
+const struct clk_ops meson_spicc_pow2_clk_ops = {
+	.recalc_rate = meson_spicc_pow2_recalc_rate,
+	.determine_rate = meson_spicc_pow2_determine_rate,
+	.set_rate = meson_spicc_pow2_set_rate,
+};
+
+static int meson_spicc_pow2_clk_init(struct meson_spicc_device *spicc)
 {
 	struct device *dev = &spicc->pdev->dev;
-	struct clk_fixed_factor *pow2_fixed_div, *enh_fixed_div;
-	struct clk_divider *pow2_div, *enh_div;
-	struct clk_mux *mux;
+	struct clk_fixed_factor *pow2_fixed_div;
 	struct clk_init_data init;
 	struct clk *clk;
 	struct clk_parent_data parent_data[2];
@@ -560,31 +611,45 @@  static int meson_spicc_clk_init(struct meson_spicc_device *spicc)
 	if (WARN_ON(IS_ERR(clk)))
 		return PTR_ERR(clk);
 
-	pow2_div = devm_kzalloc(dev, sizeof(*pow2_div), GFP_KERNEL);
-	if (!pow2_div)
-		return -ENOMEM;
-
 	snprintf(name, sizeof(name), "%s#pow2_div", dev_name(dev));
 	init.name = name;
-	init.ops = &clk_divider_ops;
-	init.flags = CLK_SET_RATE_PARENT;
+	init.ops = &meson_spicc_pow2_clk_ops;
+	/*
+	 * Set NOCACHE here to make sure we read the actual HW value
+	 * since we reset the HW after each transfer.
+	 */
+	init.flags = CLK_SET_RATE_PARENT | CLK_GET_RATE_NOCACHE;
 	parent_data[0].hw = &pow2_fixed_div->hw;
 	init.num_parents = 1;
 
-	pow2_div->shift = 16,
-	pow2_div->width = 3,
-	pow2_div->flags = CLK_DIVIDER_POWER_OF_TWO,
-	pow2_div->reg = spicc->base + SPICC_CONREG;
-	pow2_div->hw.init = &init;
+	spicc->pow2_div.shift = 16,
+	spicc->pow2_div.width = 3,
+	spicc->pow2_div.flags = CLK_DIVIDER_POWER_OF_TWO,
+	spicc->pow2_div.reg = spicc->base + SPICC_CONREG;
+	spicc->pow2_div.hw.init = &init;
 
-	clk = devm_clk_register(dev, &pow2_div->hw);
-	if (WARN_ON(IS_ERR(clk)))
-		return PTR_ERR(clk);
+	spicc->clk = devm_clk_register(dev, &spicc->pow2_div.hw);
+	if (WARN_ON(IS_ERR(spicc->clk)))
+		return PTR_ERR(spicc->clk);
 
-	if (!spicc->data->has_enhance_clk_div) {
-		spicc->clk = clk;
-		return 0;
-	}
+	return 0;
+}
+
+static int meson_spicc_enh_clk_init(struct meson_spicc_device *spicc)
+{
+	struct device *dev = &spicc->pdev->dev;
+	struct clk_fixed_factor *enh_fixed_div;
+	struct clk_divider *enh_div;
+	struct clk_mux *mux;
+	struct clk_init_data init;
+	struct clk *clk;
+	struct clk_parent_data parent_data[2];
+	char name[64];
+
+	memset(&init, 0, sizeof(init));
+	memset(&parent_data, 0, sizeof(parent_data));
+
+	init.parent_data = parent_data;
 
 	/* algorithm for enh div: rate = freq / 2 / (N + 1) */
 
@@ -637,7 +702,7 @@  static int meson_spicc_clk_init(struct meson_spicc_device *spicc)
 	snprintf(name, sizeof(name), "%s#sel", dev_name(dev));
 	init.name = name;
 	init.ops = &clk_mux_ops;
-	parent_data[0].hw = &pow2_div->hw;
+	parent_data[0].hw = &spicc->pow2_div.hw;
 	parent_data[1].hw = &enh_div->hw;
 	init.num_parents = 2;
 	init.flags = CLK_SET_RATE_PARENT;
@@ -754,12 +819,20 @@  static int meson_spicc_probe(struct platform_device *pdev)
 
 	meson_spicc_oen_enable(spicc);
 
-	ret = meson_spicc_clk_init(spicc);
+	ret = meson_spicc_pow2_clk_init(spicc);
 	if (ret) {
-		dev_err(&pdev->dev, "clock registration failed\n");
+		dev_err(&pdev->dev, "pow2 clock registration failed\n");
 		goto out_clk;
 	}
 
+	if (spicc->data->has_enhance_clk_div) {
+		ret = meson_spicc_enh_clk_init(spicc);
+		if (ret) {
+			dev_err(&pdev->dev, "clock registration failed\n");
+			goto out_clk;
+		}
+	}
+
 	ret = devm_spi_register_master(&pdev->dev, master);
 	if (ret) {
 		dev_err(&pdev->dev, "spi master registration failed\n");