[PATCH 5.15 133/244] spi: meson-spicc: add local pow2 clock ops to preserve rate between messages

Greg Kroah-Hartman
2022-08-23T10:12:29Z

From: Neil Armstrong <narmstrong@baylibre.com>

commit 09992025dacd258c823f50e82db09d7ef06cdac4 upstream.

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>
Link: https://lore.kernel.org/r/20220811134445.678446-1-narmstrong@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/spi/spi-meson-spicc.c | 129 ++++++++++++++++++++++++++++++++----------
1 file changed, 101 insertions(+), 28 deletions(-)

--- 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(s
{
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(s
/* 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(s
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 s
* 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 m
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 m
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 plat

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");