bus: sunxi-rsb: Support atomic transfers

When communicating with a PMIC during system poweroff (pm_power_off()),
IRQs are disabled and we are in a RCU read-side critical section, so we
cannot use wait_for_completion_io_timeout(). Instead, poll the status
register for transfer completion.

Fixes: d787dcdb9c8f ("bus: sunxi-rsb: Add driver for Allwinner Reduced Serial Bus")
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20221114015749.28490-3-samuel@sholland.org
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>

diff --git a/drivers/bus/sunxi-rsb.c b/drivers/bus/sunxi-rsb.c
index 17343cd..3aa91ae 100644 (file)
--- a/drivers/bus/sunxi-rsb.c
+++ b/drivers/bus/sunxi-rsb.c
@@ -267,6 +267,9 @@ EXPORT_SYMBOL_GPL(sunxi_rsb_driver_register);
 /* common code that starts a transfer */
 static int _sunxi_rsb_run_xfer(struct sunxi_rsb *rsb)
 {
+       u32 int_mask, status;
+       bool timeout;
+
        if (readl(rsb->regs + RSB_CTRL) & RSB_CTRL_START_TRANS) {
                dev_dbg(rsb->dev, "RSB transfer still in progress\n");
                return -EBUSY;
@@ -274,13 +277,23 @@ static int _sunxi_rsb_run_xfer(struct sunxi_rsb *rsb)
 
        reinit_completion(&rsb->complete);
 
-       writel(RSB_INTS_LOAD_BSY | RSB_INTS_TRANS_ERR | RSB_INTS_TRANS_OVER,
-              rsb->regs + RSB_INTE);
+       int_mask = RSB_INTS_LOAD_BSY | RSB_INTS_TRANS_ERR | RSB_INTS_TRANS_OVER;
+       writel(int_mask, rsb->regs + RSB_INTE);
        writel(RSB_CTRL_START_TRANS | RSB_CTRL_GLOBAL_INT_ENB,
               rsb->regs + RSB_CTRL);
 
-       if (!wait_for_completion_io_timeout(&rsb->complete,
-                                           msecs_to_jiffies(100))) {
+       if (irqs_disabled()) {
+               timeout = readl_poll_timeout_atomic(rsb->regs + RSB_INTS,
+                                                   status, (status & int_mask),
+                                                   10, 100000);
+               writel(status, rsb->regs + RSB_INTS);
+       } else {
+               timeout = !wait_for_completion_io_timeout(&rsb->complete,
+                                                         msecs_to_jiffies(100));
+               status = rsb->status;
+       }
+
+       if (timeout) {
                dev_dbg(rsb->dev, "RSB timeout\n");
 
                /* abort the transfer */
@@ -292,18 +305,18 @@ static int _sunxi_rsb_run_xfer(struct sunxi_rsb *rsb)
                return -ETIMEDOUT;
        }
 
-       if (rsb->status & RSB_INTS_LOAD_BSY) {
+       if (status & RSB_INTS_LOAD_BSY) {
                dev_dbg(rsb->dev, "RSB busy\n");
                return -EBUSY;
        }
 
-       if (rsb->status & RSB_INTS_TRANS_ERR) {
-               if (rsb->status & RSB_INTS_TRANS_ERR_ACK) {
+       if (status & RSB_INTS_TRANS_ERR) {
+               if (status & RSB_INTS_TRANS_ERR_ACK) {
                        dev_dbg(rsb->dev, "RSB slave nack\n");
                        return -EINVAL;
                }
 
-               if (rsb->status & RSB_INTS_TRANS_ERR_DATA) {
+               if (status & RSB_INTS_TRANS_ERR_DATA) {
                        dev_dbg(rsb->dev, "RSB transfer data error\n");
                        return -EIO;
                }