[PATCH v4 6/7] spi: cadence-xspi: Add support for panic writes

[Paul Cercueil]

From: Tanmay Jagdale <tanmay@xxxxxxxxxxx>

Advertise support for panic writes. When a memory op is received with
the 'panic' flag set, the driver will then work without relying on
interrupts and without sleeping.

Signed-off-by: Tanmay Jagdale <tanmay@xxxxxxxxxxx>
Co-developed-by: Paul Cercueil <paul.cercueil@xxxxxxxxxxx>
Signed-off-by: Paul Cercueil <paul.cercueil@xxxxxxxxxxx>
---

Notes:
    v2: - Don't enable interrupts if doing a panic write
        - Use a new cdns_readl_poll() macro that will resolve to calling
          readl_relaxed_poll_timeout_atomic() when doing a panic write, or
          readl_relaxed_poll_timeout() otherwise.
        - Drop cdns_xspi->panic_write. We don't actually need to check it in
          cdns_xspi_is_dll_locked(), because this code is never called in
          the kernel panic path.
    
    v3-v4: No change

 drivers/spi/spi-cadence-xspi.c | 52 ++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 25 deletions(-)

diff --git a/drivers/spi/spi-cadence-xspi.c b/drivers/spi/spi-cadence-xspi.c
index 2a2a40bf0a4c..a7fd715c45d5 100644
--- a/drivers/spi/spi-cadence-xspi.c
+++ b/drivers/spi/spi-cadence-xspi.c
@@ -287,6 +287,10 @@
 #define GENERIC_CMD_REG_3_NEEDED(len)		(len > 7)
 #define GENERIC_CMD_REG_2_NEEDED(len)		(len > 3)
 
+#define cdns_readl_poll(addr, val, cond, delay_us, timeout_us, can_sleep) \
+	((can_sleep) ? readl_relaxed_poll_timeout(addr, val, cond, delay_us, timeout_us) \
+		     : readl_relaxed_poll_timeout_atomic(addr, val, cond, delay_us, timeout_us))
+
 enum cdns_xspi_stig_instr_type {
 	CDNS_XSPI_STIG_INSTR_TYPE_0,
 	CDNS_XSPI_STIG_INSTR_TYPE_1,
@@ -353,40 +357,33 @@ struct cdns_xspi_dev {
 	int current_xfer_qword;
 };
 
-static int cdns_xspi_wait_for_controller_idle(struct cdns_xspi_dev *cdns_xspi)
+static int cdns_xspi_wait_for_controller_idle(struct cdns_xspi_dev *cdns_xspi, bool sleep)
 {
 	u32 ctrl_stat;
 
-	return readl_relaxed_poll_timeout(cdns_xspi->iobase +
-					  CDNS_XSPI_CTRL_STATUS_REG,
-					  ctrl_stat,
-					  ((ctrl_stat &
-					    CDNS_XSPI_CTRL_BUSY) == 0),
-					  100, 1000);
+	return cdns_readl_poll(cdns_xspi->iobase + CDNS_XSPI_CTRL_STATUS_REG,
+			       ctrl_stat, !(ctrl_stat & CDNS_XSPI_CTRL_BUSY),
+			       100, 1000, sleep);
 }
 
 static bool cdns_xspi_is_stig_ready(struct cdns_xspi_dev *cdns_xspi, bool sleep)
 {
 	u32 ctrl_stat;
 
-	return !readl_relaxed_poll_timeout
-		(cdns_xspi->iobase + CDNS_XSPI_CTRL_STATUS_REG,
-		ctrl_stat,
-		((ctrl_stat & BIT(3)) == 0),
-		sleep ? MRVL_XSPI_POLL_DELAY_US : 0,
-		sleep ? MRVL_XSPI_POLL_TIMEOUT_US : 0);
+	return !cdns_readl_poll(cdns_xspi->iobase + CDNS_XSPI_CTRL_STATUS_REG,
+				ctrl_stat, !(ctrl_stat & BIT(3)),
+				MRVL_XSPI_POLL_DELAY_US,
+				MRVL_XSPI_POLL_TIMEOUT_US, sleep);
 }
 
 static bool cdns_xspi_is_sdma_ready(struct cdns_xspi_dev *cdns_xspi, bool sleep)
 {
 	u32 ctrl_stat;
 
-	if (readl_relaxed_poll_timeout
-	    (cdns_xspi->iobase + CDNS_XSPI_INTR_STATUS_REG,
-	     ctrl_stat,
-	     (ctrl_stat & CDNS_XSPI_SDMA_TRIGGER),
-	     sleep ? MRVL_XSPI_POLL_DELAY_US : 0,
-	     sleep ? MRVL_XSPI_POLL_TIMEOUT_US : 0)) {
+	if (cdns_readl_poll(cdns_xspi->iobase + CDNS_XSPI_INTR_STATUS_REG,
+			    ctrl_stat, (ctrl_stat & CDNS_XSPI_SDMA_TRIGGER),
+			    MRVL_XSPI_POLL_DELAY_US, MRVL_XSPI_POLL_TIMEOUT_US,
+			    sleep)) {
 		return false;
 	}
 
@@ -557,14 +554,14 @@ static int cdns_xspi_send_stig_command(struct cdns_xspi_dev *cdns_xspi,
 	int ret;
 	int dummybytes = op->dummy.nbytes;
 
-	ret = cdns_xspi_wait_for_controller_idle(cdns_xspi);
+	ret = cdns_xspi_wait_for_controller_idle(cdns_xspi, !op->panic_write);
 	if (ret < 0)
 		return -EIO;
 
 	writel(FIELD_PREP(CDNS_XSPI_CTRL_WORK_MODE, CDNS_XSPI_WORK_MODE_STIG),
 	       cdns_xspi->iobase + CDNS_XSPI_CTRL_CONFIG_REG);
 
-	if (cdns_xspi->irq >= 0)
+	if (cdns_xspi->irq >= 0 && !op->panic_write)
 		cdns_xspi->set_interrupts_handler(cdns_xspi, true);
 	cdns_xspi->sdma_error = false;
 
@@ -595,23 +592,23 @@ static int cdns_xspi_send_stig_command(struct cdns_xspi_dev *cdns_xspi,
 
 		cdns_xspi_trigger_command(cdns_xspi, cmd_regs);
 
-		if (cdns_xspi->irq >= 0) {
+		if (cdns_xspi->irq >= 0 && !op->panic_write) {
 			wait_for_completion(&cdns_xspi->sdma_complete);
 			if (cdns_xspi->sdma_error) {
 				cdns_xspi->set_interrupts_handler(cdns_xspi, false);
 				return -EIO;
 			}
-		} else if (!cdns_xspi_is_sdma_ready(cdns_xspi, true)) {
+		} else if (!cdns_xspi_is_sdma_ready(cdns_xspi, !op->panic_write)) {
 			return -EIO;
 		}
 
 		cdns_xspi->sdma_handler(cdns_xspi);
 	}
 
-	if (cdns_xspi->irq >= 0) {
+	if (cdns_xspi->irq >= 0 && !op->panic_write) {
 		wait_for_completion(&cdns_xspi->cmd_complete);
 		cdns_xspi->set_interrupts_handler(cdns_xspi, false);
-	} else if (!cdns_xspi_is_stig_ready(cdns_xspi, true)) {
+	} else if (!cdns_xspi_is_stig_ready(cdns_xspi, !op->panic_write)) {
 		return -EIO;
 	}
 
@@ -1195,6 +1192,10 @@ static int cdns_xspi_transfer_one_message_b0(struct spi_controller *controller,
 }
 #endif
 
+static const struct spi_controller_mem_caps cdns_xspi_mem_caps = {
+	.panic_write = true,
+};
+
 static int cdns_xspi_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -1315,6 +1316,7 @@ static int cdns_xspi_probe(struct platform_device *pdev)
 	}
 
 	host->num_chipselect = 1 << cdns_xspi->hw_num_banks;
+	host->mem_caps = &cdns_xspi_mem_caps;
 
 	ret = devm_spi_register_controller(dev, host);
 	if (ret) {
-- 
2.47.3