Merge series "spi: spi-geni-qcom: Fixes / perf improvements" from Douglas...

Merge series "spi: spi-geni-qcom: Fixes / perf improvements" from Douglas Anderson <dianders@chromium.org>:

This patch series is a new version of the previous patch posted:
  [PATCH v2] spi: spi-geni-qcom: Speculative fix of "nobody cared" about interrupt
  https://lore.kernel.org/r/20200317133653.v2.1.I752ebdcfd5e8bf0de06d66e767b8974932b3620e@changeid

At this point I've done enough tracing to know that there was a real
race in the old code (not just weakly ordered memory problems) and
that should be fixed with the locking patches.

While looking at this driver, I also noticed we weren't properly
noting error interrupts and also weren't actually using our FIFO
effectively, so I fixed those.

The last patch in the series addresses review feedback about dislike
for the "cur_mcmd" state variable.  It also could possibly make
"abort" work ever-so-slightly more reliably.

Changes in v4:
- Drop 'controller' in comment.
- Use Stephen's diagram to explain the race better.

Changes in v3:
- ("spi: spi-geni-qcom: No need for irqsave variant...") new for v3
- Split out some lock cleanup to previous patch.
- Don't need to read IRQ status register inside spinlock.
- Don't check for state CMD_NONE; later patch is removing state var.
- Don't hold the lock for all of setup_fifo_xfer().
- Comment about why it's safe to Ack interrupts at the end.
- Subject/desc changed since race is definitely there.
- ("spi: spi-geni-qcom: Check for error IRQs") new in v3.
- ("spi: spi-geni-qcom: Actually use our FIFO") new in v3.
- ("spi: spi-geni-qcom: Don't keep a local state variable") new in v3.

Changes in v2:
- Detect true spurious interrupt.
- Still return IRQ_NONE for state machine mismatch, but print warn.

Douglas Anderson (5):
  spi: spi-geni-qcom: No need for irqsave variant of spinlock calls
  spi: spi-geni-qcom: Mo' betta locking
  spi: spi-geni-qcom: Check for error IRQs
  spi: spi-geni-qcom: Actually use our FIFO
  spi: spi-geni-qcom: Don't keep a local state variable

 drivers/spi/spi-geni-qcom.c | 120 ++++++++++++++++++++++++------------
 1 file changed, 81 insertions(+), 39 deletions(-)

--
2.27.0.290.gba653c62da-goog

drivers/spi/spi-geni-qcom.c

@@ -63,13 +63,6 @@
 #define TIMESTAMP_AFTER		BIT(3)
 #define POST_CMD_DELAY		BIT(4)
 
-enum spi_m_cmd_opcode {
-	CMD_NONE,
-	CMD_XFER,
-	CMD_CS,
-	CMD_CANCEL,
-};
-
 struct spi_geni_master {
 	struct geni_se se;
 	struct device *dev;
@@ -81,10 +74,11 @@ struct spi_geni_master {
 	unsigned int tx_rem_bytes;
 	unsigned int rx_rem_bytes;
 	const struct spi_transfer *cur_xfer;
-	struct completion xfer_done;
+	struct completion cs_done;
+	struct completion cancel_done;
+	struct completion abort_done;
 	unsigned int oversampling;
 	spinlock_t lock;
-	enum spi_m_cmd_opcode cur_mcmd;
 	int irq;
 };
 
@@ -126,20 +120,23 @@ static void handle_fifo_timeout(struct spi_master *spi,
 	struct geni_se *se = &mas->se;
 
 	spin_lock_irq(&mas->lock);
-	reinit_completion(&mas->xfer_done);
-	mas->cur_mcmd = CMD_CANCEL;
-	geni_se_cancel_m_cmd(se);
+	reinit_completion(&mas->cancel_done);
 	writel(0, se->base + SE_GENI_TX_WATERMARK_REG);
+	mas->cur_xfer = NULL;
+	mas->tx_rem_bytes = mas->rx_rem_bytes = 0;
+	geni_se_cancel_m_cmd(se);
 	spin_unlock_irq(&mas->lock);
-	time_left = wait_for_completion_timeout(&mas->xfer_done, HZ);
+
+	time_left = wait_for_completion_timeout(&mas->cancel_done, HZ);
 	if (time_left)
 		return;
 
 	spin_lock_irq(&mas->lock);
-	reinit_completion(&mas->xfer_done);
+	reinit_completion(&mas->abort_done);
 	geni_se_abort_m_cmd(se);
 	spin_unlock_irq(&mas->lock);
-	time_left = wait_for_completion_timeout(&mas->xfer_done, HZ);
+
+	time_left = wait_for_completion_timeout(&mas->abort_done, HZ);
 	if (!time_left)
 		dev_err(mas->dev, "Failed to cancel/abort m_cmd\n");
 }
@@ -151,18 +148,19 @@ static void spi_geni_set_cs(struct spi_device *slv, bool set_flag)
 	struct geni_se *se = &mas->se;
 	unsigned long time_left;
 
-	reinit_completion(&mas->xfer_done);
 	pm_runtime_get_sync(mas->dev);
 	if (!(slv->mode & SPI_CS_HIGH))
 		set_flag = !set_flag;
 
-	mas->cur_mcmd = CMD_CS;
+	spin_lock_irq(&mas->lock);
+	reinit_completion(&mas->cs_done);
 	if (set_flag)
 		geni_se_setup_m_cmd(se, SPI_CS_ASSERT, 0);
 	else
 		geni_se_setup_m_cmd(se, SPI_CS_DEASSERT, 0);
+	spin_unlock_irq(&mas->lock);
 
-	time_left = wait_for_completion_timeout(&mas->xfer_done, HZ);
+	time_left = wait_for_completion_timeout(&mas->cs_done, HZ);
 	if (!time_left)
 		handle_fifo_timeout(spi, NULL);
 
@@ -283,7 +281,7 @@ static int spi_geni_init(struct spi_geni_master *mas)
 	 * Hardware programming guide suggests to configure
 	 * RX FIFO RFR level to fifo_depth-2.
 	 */
-	geni_se_init(se, 0x0, mas->tx_fifo_depth - 2);
+	geni_se_init(se, mas->tx_fifo_depth / 2, mas->tx_fifo_depth - 2);
 	/* Transmit an entire FIFO worth of data per IRQ */
 	mas->tx_wm = 1;
 	ver = geni_se_get_qup_hw_version(se);
@@ -307,6 +305,21 @@ static void setup_fifo_xfer(struct spi_transfer *xfer,
 	u32 spi_tx_cfg, len;
 	struct geni_se *se = &mas->se;
 
+	/*
+	 * Ensure that our interrupt handler isn't still running from some
+	 * prior command before we start messing with the hardware behind
+	 * its back.  We don't need to _keep_ the lock here since we're only
+	 * worried about racing with out interrupt handler.  The SPI core
+	 * already handles making sure that we're not trying to do two
+	 * transfers at once or setting a chip select and doing a transfer
+	 * concurrently.
+	 *
+	 * NOTE: we actually _can't_ hold the lock here because possibly we
+	 * might call clk_set_rate() which needs to be able to sleep.
+	 */
+	spin_lock_irq(&mas->lock);
+	spin_unlock_irq(&mas->lock);
+
 	spi_tx_cfg = readl(se->base + SE_SPI_TRANS_CFG);
 	if (xfer->bits_per_word != mas->cur_bits_per_word) {
 		spi_setup_word_len(mas, mode, xfer->bits_per_word);
@@ -366,7 +379,12 @@ static void setup_fifo_xfer(struct spi_transfer *xfer,
 		mas->rx_rem_bytes = xfer->len;
 	}
 	writel(spi_tx_cfg, se->base + SE_SPI_TRANS_CFG);
-	mas->cur_mcmd = CMD_XFER;
+
+	/*
+	 * Lock around right before we start the transfer since our
+	 * interrupt could come in at any time now.
+	 */
+	spin_lock_irq(&mas->lock);
 	geni_se_setup_m_cmd(se, m_cmd, FRAGMENTATION);
 
 	/*
@@ -376,6 +394,7 @@ static void setup_fifo_xfer(struct spi_transfer *xfer,
 	 */
 	if (m_cmd & SPI_TX_ONLY)
 		writel(mas->tx_wm, se->base + SE_GENI_TX_WATERMARK_REG);
+	spin_unlock_irq(&mas->lock);
 }
 
 static int spi_geni_transfer_one(struct spi_master *spi,
@@ -478,11 +497,16 @@ static irqreturn_t geni_spi_isr(int irq, void *data)
 	struct geni_se *se = &mas->se;
 	u32 m_irq;
 
-	if (mas->cur_mcmd == CMD_NONE)
+	m_irq = readl(se->base + SE_GENI_M_IRQ_STATUS);
+	if (!m_irq)
 		return IRQ_NONE;
 
+	if (m_irq & (M_CMD_OVERRUN_EN | M_ILLEGAL_CMD_EN | M_CMD_FAILURE_EN |
+		     M_RX_FIFO_RD_ERR_EN | M_RX_FIFO_WR_ERR_EN |
+		     M_TX_FIFO_RD_ERR_EN | M_TX_FIFO_WR_ERR_EN))
+		dev_warn(mas->dev, "Unexpected IRQ err status %#010x\n", m_irq);
+
 	spin_lock(&mas->lock);
-	m_irq = readl(se->base + SE_GENI_M_IRQ_STATUS);
 
 	if ((m_irq & M_RX_FIFO_WATERMARK_EN) || (m_irq & M_RX_FIFO_LAST_EN))
 		geni_spi_handle_rx(mas);
@@ -491,11 +515,13 @@ static irqreturn_t geni_spi_isr(int irq, void *data)
 		geni_spi_handle_tx(mas);
 
 	if (m_irq & M_CMD_DONE_EN) {
-		if (mas->cur_mcmd == CMD_XFER)
+		if (mas->cur_xfer) {
 			spi_finalize_current_transfer(spi);
-		else if (mas->cur_mcmd == CMD_CS)
-			complete(&mas->xfer_done);
-		mas->cur_mcmd = CMD_NONE;
+			mas->cur_xfer = NULL;
+		} else {
+			complete(&mas->cs_done);
+		}
+
 		/*
 		 * If this happens, then a CMD_DONE came before all the Tx
 		 * buffer bytes were sent out. This is unusual, log this
@@ -517,13 +543,28 @@ static irqreturn_t geni_spi_isr(int irq, void *data)
 				mas->rx_rem_bytes, mas->cur_bits_per_word);
 	}
 
-	if ((m_irq & M_CMD_CANCEL_EN) || (m_irq & M_CMD_ABORT_EN)) {
-		mas->cur_mcmd = CMD_NONE;
-		complete(&mas->xfer_done);
-	}
+	if (m_irq & M_CMD_CANCEL_EN)
+		complete(&mas->cancel_done);
+	if (m_irq & M_CMD_ABORT_EN)
+		complete(&mas->abort_done);
 
+	/*
+	 * It's safe or a good idea to Ack all of our our interrupts at the
+	 * end of the function. Specifically:
+	 * - M_CMD_DONE_EN / M_RX_FIFO_LAST_EN: Edge triggered interrupts and
+	 *   clearing Acks. Clearing at the end relies on nobody else having
+	 *   started a new transfer yet or else we could be clearing _their_
+	 *   done bit, but everyone grabs the spinlock before starting a new
+	 *   transfer.
+	 * - M_RX_FIFO_WATERMARK_EN / M_TX_FIFO_WATERMARK_EN: These appear
+	 *   to be "latched level" interrupts so it's important to clear them
+	 *   _after_ you've handled the condition and always safe to do so
+	 *   since they'll re-assert if they're still happening.
+	 */
 	writel(m_irq, se->base + SE_GENI_M_IRQ_CLEAR);
+
 	spin_unlock(&mas->lock);
+
 	return IRQ_HANDLED;
 }
 
@@ -573,7 +614,9 @@ static int spi_geni_probe(struct platform_device *pdev)
 	spi->handle_err = handle_fifo_timeout;
 	spi->set_cs = spi_geni_set_cs;
 
-	init_completion(&mas->xfer_done);
+	init_completion(&mas->cs_done);
+	init_completion(&mas->cancel_done);
+	init_completion(&mas->abort_done);
 	spin_lock_init(&mas->lock);
 	pm_runtime_enable(dev);