diff mbox series

[1/8] spmi: mtk-pmif: Serialize PMIF status check and command submission

Message ID 20231206231733.4031901-2-sboyd@kernel.org
State New
Headers
Series SPMI patches for the merge window |

Commit Message

Stephen Boyd Dec. 6, 2023, 11:17 p.m. UTC 
  From: Nícolas F. R. A. Prado <nfraprado@collabora.com>

Before writing the read or write command to the SPMI arbiter through the
PMIF interface, the current status of the channel is checked to ensure
it is idle. However, since the status only changes from idle when the
command is written, it is possible for two concurrent calls to determine
that the channel is idle and simultaneously send their commands. At this
point the PMIF interface hangs, with the status register no longer being
updated, and thus causing all subsequent operations to time out.

This was observed on the mt8195-cherry-tomato-r2 machine, particularly
after commit 46600ab142f8 ("regulator: Set PROBE_PREFER_ASYNCHRONOUS for
drivers between 5.10 and 5.15") was applied, since then the two MT6315
devices present on the SPMI bus would probe assynchronously and
sometimes (during probe or at a later point) read the bus
simultaneously, breaking the PMIF interface and consequently slowing
down the whole system.

To fix the issue at its root cause, introduce locking around the channel
status check and the command write, so that both become an atomic
operation, preventing race conditions between two (or more) SPMI bus
read/write operations. A spinlock is used since this is a fast bus, as
indicated by the usage of the atomic variant of readl_poll, and
'.fast_io = true' being used in the mt6315 driver, so spinlocks are
already used for the regmap access.

Fixes: b45b3ccef8c0 ("spmi: mediatek: Add support for MT6873/8192")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20230724154739.493724-1-nfraprado@collabora.com
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
---
 drivers/spmi/spmi-mtk-pmif.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

Comments

Greg KH Dec. 15, 2023, 4:12 p.m. UTC | #1 
On Wed, Dec 06, 2023 at 03:17:24PM -0800, Stephen Boyd wrote:
> From: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> 
> Before writing the read or write command to the SPMI arbiter through the
> PMIF interface, the current status of the channel is checked to ensure
> it is idle. However, since the status only changes from idle when the
> command is written, it is possible for two concurrent calls to determine
> that the channel is idle and simultaneously send their commands. At this
> point the PMIF interface hangs, with the status register no longer being
> updated, and thus causing all subsequent operations to time out.
> 
> This was observed on the mt8195-cherry-tomato-r2 machine, particularly
> after commit 46600ab142f8 ("regulator: Set PROBE_PREFER_ASYNCHRONOUS for
> drivers between 5.10 and 5.15") was applied, since then the two MT6315
> devices present on the SPMI bus would probe assynchronously and
> sometimes (during probe or at a later point) read the bus
> simultaneously, breaking the PMIF interface and consequently slowing
> down the whole system.
> 
> To fix the issue at its root cause, introduce locking around the channel
> status check and the command write, so that both become an atomic
> operation, preventing race conditions between two (or more) SPMI bus
> read/write operations. A spinlock is used since this is a fast bus, as
> indicated by the usage of the atomic variant of readl_poll, and
> '.fast_io = true' being used in the mt6315 driver, so spinlocks are
> already used for the regmap access.
> 
> Fixes: b45b3ccef8c0 ("spmi: mediatek: Add support for MT6873/8192")
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> Link: https://lore.kernel.org/r/20230724154739.493724-1-nfraprado@collabora.com
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
> Signed-off-by: Stephen Boyd <sboyd@kernel.org>
> ---
>  drivers/spmi/spmi-mtk-pmif.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- You have marked a patch with a "Fixes:" tag for a commit that is in an
  older released kernel, yet you do not have a cc: stable line in the
  signed-off-by area at all, which means that the patch will not be
  applied to any older kernel releases.  To properly fix this, please
  follow the documented rules in the
  Documentation/process/stable-kernel-rules.rst file for how to resolve
  this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
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thanks,

greg k-h's patch email bot
diff mbox series

Patch

diff --git a/drivers/spmi/spmi-mtk-pmif.c b/drivers/spmi/spmi-mtk-pmif.c
index b3c991e1ea40..54c35f5535cb 100644
--- a/drivers/spmi/spmi-mtk-pmif.c
+++ b/drivers/spmi/spmi-mtk-pmif.c
@@ -50,6 +50,7 @@  struct pmif {
 	struct clk_bulk_data clks[PMIF_MAX_CLKS];
 	size_t nclks;
 	const struct pmif_data *data;
+	raw_spinlock_t lock;
 };
 
 static const char * const pmif_clock_names[] = {
@@ -314,6 +315,7 @@  static int pmif_spmi_read_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	struct ch_reg *inf_reg;
 	int ret;
 	u32 data, cmd;
+	unsigned long flags;
 
 	/* Check for argument validation. */
 	if (sid & ~0xf) {
@@ -334,6 +336,7 @@  static int pmif_spmi_read_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	else
 		return -EINVAL;
 
+	raw_spin_lock_irqsave(&arb->lock, flags);
 	/* Wait for Software Interface FSM state to be IDLE. */
 	inf_reg = &arb->chan;
 	ret = readl_poll_timeout_atomic(arb->base + arb->data->regs[inf_reg->ch_sta],
@@ -343,6 +346,7 @@  static int pmif_spmi_read_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 		/* set channel ready if the data has transferred */
 		if (pmif_is_fsm_vldclr(arb))
 			pmif_writel(arb, 1, inf_reg->ch_rdy);
+		raw_spin_unlock_irqrestore(&arb->lock, flags);
 		dev_err(&ctrl->dev, "failed to wait for SWINF_IDLE\n");
 		return ret;
 	}
@@ -350,6 +354,7 @@  static int pmif_spmi_read_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	/* Send the command. */
 	cmd = (opc << 30) | (sid << 24) | ((len - 1) << 16) | addr;
 	pmif_writel(arb, cmd, inf_reg->ch_send);
+	raw_spin_unlock_irqrestore(&arb->lock, flags);
 
 	/*
 	 * Wait for Software Interface FSM state to be WFVLDCLR,
@@ -376,7 +381,8 @@  static int pmif_spmi_write_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	struct pmif *arb = spmi_controller_get_drvdata(ctrl);
 	struct ch_reg *inf_reg;
 	int ret;
-	u32 data, cmd;
+	u32 data, wdata, cmd;
+	unsigned long flags;
 
 	if (len > 4) {
 		dev_err(&ctrl->dev, "pmif supports 1..4 bytes per trans, but:%zu requested", len);
@@ -394,6 +400,10 @@  static int pmif_spmi_write_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	else
 		return -EINVAL;
 
+	/* Set the write data. */
+	memcpy(&wdata, buf, len);
+
+	raw_spin_lock_irqsave(&arb->lock, flags);
 	/* Wait for Software Interface FSM state to be IDLE. */
 	inf_reg = &arb->chan;
 	ret = readl_poll_timeout_atomic(arb->base + arb->data->regs[inf_reg->ch_sta],
@@ -403,17 +413,17 @@  static int pmif_spmi_write_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 		/* set channel ready if the data has transferred */
 		if (pmif_is_fsm_vldclr(arb))
 			pmif_writel(arb, 1, inf_reg->ch_rdy);
+		raw_spin_unlock_irqrestore(&arb->lock, flags);
 		dev_err(&ctrl->dev, "failed to wait for SWINF_IDLE\n");
 		return ret;
 	}
 
-	/* Set the write data. */
-	memcpy(&data, buf, len);
-	pmif_writel(arb, data, inf_reg->wdata);
+	pmif_writel(arb, wdata, inf_reg->wdata);
 
 	/* Send the command. */
 	cmd = (opc << 30) | BIT(29) | (sid << 24) | ((len - 1) << 16) | addr;
 	pmif_writel(arb, cmd, inf_reg->ch_send);
+	raw_spin_unlock_irqrestore(&arb->lock, flags);
 
 	return 0;
 }
@@ -488,6 +498,8 @@  static int mtk_spmi_probe(struct platform_device *pdev)
 	arb->chan.ch_send = PMIF_SWINF_0_ACC + chan_offset;
 	arb->chan.ch_rdy = PMIF_SWINF_0_VLD_CLR + chan_offset;
 
+	raw_spin_lock_init(&arb->lock);
+
 	platform_set_drvdata(pdev, ctrl);
 
 	err = spmi_controller_add(ctrl);