dmaengine: stm32-dma3: introduce channel semaphore helpers

Before restoring semaphore status after suspend, introduce new functions
to handle semaphore operations :
- stm32_dma3_get_chan_sem() to take the semaphore
- stm32_dma3_put_chan_sem() to release the semaphore
Also, use a new boolean variable semaphore_taken, which is true when the
semaphore has been taken and false when it has been released.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://patch.msgid.link/20251121-dma3_improv-v2-2-76a207b13ea6@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/stm32/stm32-dma3.c b/drivers/dma/stm32/stm32-dma3.c
index 9500164c8f68884f721ce46dad1e086b87e97eeb..a1583face7ec3f952bb9bbff2705c86947811ea8 100644 (file)
--- a/drivers/dma/stm32/stm32-dma3.c
+++ b/drivers/dma/stm32/stm32-dma3.c
@@ -288,6 +288,7 @@ struct stm32_dma3_chan {
        u32 fifo_size;
        u32 max_burst;
        bool semaphore_mode;
+       bool semaphore_taken;
        struct stm32_dma3_dt_conf dt_config;
        struct dma_slave_config dma_config;
        u8 config_set;
@@ -1063,11 +1064,50 @@ static irqreturn_t stm32_dma3_chan_irq(int irq, void *devid)
        return IRQ_HANDLED;
 }
 
+static int stm32_dma3_get_chan_sem(struct stm32_dma3_chan *chan)
+{
+       struct stm32_dma3_ddata *ddata = to_stm32_dma3_ddata(chan);
+       u32 csemcr, ccid;
+
+       csemcr = readl_relaxed(ddata->base + STM32_DMA3_CSEMCR(chan->id));
+       /* Make an attempt to take the channel semaphore if not already taken */
+       if (!(csemcr & CSEMCR_SEM_MUTEX)) {
+               writel_relaxed(CSEMCR_SEM_MUTEX, ddata->base + STM32_DMA3_CSEMCR(chan->id));
+               csemcr = readl_relaxed(ddata->base + STM32_DMA3_CSEMCR(chan->id));
+       }
+
+       /* Check if channel is under CID1 control */
+       ccid = FIELD_GET(CSEMCR_SEM_CCID, csemcr);
+       if (!(csemcr & CSEMCR_SEM_MUTEX) || ccid != CCIDCFGR_CID1)
+               goto bad_cid;
+
+       chan->semaphore_taken = true;
+       dev_dbg(chan2dev(chan), "under CID1 control (semcr=0x%08x)\n", csemcr);
+
+       return 0;
+
+bad_cid:
+       chan->semaphore_taken = false;
+       dev_err(chan2dev(chan), "not under CID1 control (in-use by CID%d)\n", ccid);
+
+       return -EACCES;
+}
+
+static void stm32_dma3_put_chan_sem(struct stm32_dma3_chan *chan)
+{
+       struct stm32_dma3_ddata *ddata = to_stm32_dma3_ddata(chan);
+
+       if (chan->semaphore_taken) {
+               writel_relaxed(0, ddata->base + STM32_DMA3_CSEMCR(chan->id));
+               chan->semaphore_taken = false;
+               dev_dbg(chan2dev(chan), "no more under CID1 control\n");
+       }
+}
+
 static int stm32_dma3_alloc_chan_resources(struct dma_chan *c)
 {
        struct stm32_dma3_chan *chan = to_stm32_dma3_chan(c);
        struct stm32_dma3_ddata *ddata = to_stm32_dma3_ddata(chan);
-       u32 id = chan->id, csemcr, ccid;
        int ret;
 
        ret = pm_runtime_resume_and_get(ddata->dma_dev.dev);
@@ -1092,16 +1132,9 @@ static int stm32_dma3_alloc_chan_resources(struct dma_chan *c)
 
        /* Take the channel semaphore */
        if (chan->semaphore_mode) {
-               writel_relaxed(CSEMCR_SEM_MUTEX, ddata->base + STM32_DMA3_CSEMCR(id));
-               csemcr = readl_relaxed(ddata->base + STM32_DMA3_CSEMCR(id));
-               ccid = FIELD_GET(CSEMCR_SEM_CCID, csemcr);
-               /* Check that the channel is well taken */
-               if (ccid != CCIDCFGR_CID1) {
-                       dev_err(chan2dev(chan), "Not under CID1 control (in-use by CID%d)\n", ccid);
-                       ret = -EPERM;
+               ret = stm32_dma3_get_chan_sem(chan);
+               if (ret)
                        goto err_pool_destroy;
-               }
-               dev_dbg(chan2dev(chan), "Under CID1 control (semcr=0x%08x)\n", csemcr);
        }
 
        return 0;
@@ -1135,7 +1168,7 @@ static void stm32_dma3_free_chan_resources(struct dma_chan *c)
 
        /* Release the channel semaphore */
        if (chan->semaphore_mode)
-               writel_relaxed(0, ddata->base + STM32_DMA3_CSEMCR(chan->id));
+               stm32_dma3_put_chan_sem(chan);
 
        pm_runtime_put_sync(ddata->dma_dev.dev);