dmaengine: sh: rz-dmac: Add runtime PM support

Protect the driver exposed APIs with runtime PM suspend/resume calls
before accessing HW registers. As the current driver leaves runtime PM
enabled in probe, the purpose of the changes in this patch is to avoid
accessing HW registers after a failed system suspend leaves the runtime
PM state of the device improperly reinitialized.

In that case, the driver remains bound to the device, the APIs are still
exposed, and any access to HW registers without runtime resuming the
device may lead to synchronous aborts.

To avoid leaking resources in case of runtime PM failures, save the error
code returned by PM_RUNTIME_ACQUIRE_ERR() in rz_dmac_terminate_all() and
return it only at the end of the function to allow the cleanup code to
run. A similar approach is used in rz_dmac_free_chan_resources().

Because some exposed APIs (e.g. ->device_terminate_all()) may be called
from atomic context according to the documentation, mark the DMA device as
pm_runtime_irq_safe().

This patch prepares the driver for suspend-to-RAM support.

Tested-by: John Madieu <john.madieu.xa@bp.renesas.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Link: https://patch.msgid.link/20260526084710.3491480-15-claudiu.beznea@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
index 93394b9934c8967aab55a2f216cba9938a209c6b..bd4ca8e939f17eca0e7d8e605f3b8b5a640e650e 100644 (file)
--- a/drivers/dma/sh/rz-dmac.c
+++ b/drivers/dma/sh/rz-dmac.c
@@ -549,12 +549,22 @@ static void rz_dmac_free_chan_resources(struct dma_chan *chan)
        struct rz_dmac *dmac = to_rz_dmac(chan->device);
        struct rz_dmac_desc *desc, *_desc;
        unsigned long flags;
+       int ret;
+
+       PM_RUNTIME_ACQUIRE_IF_ENABLED(dmac->dev, pm);
+       ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+       if (ret) {
+               dev_err(dmac->dev, "RPM resume failed for channel %s, ret=%d\n!",
+                       dma_chan_name(chan), ret);
+       }
 
        spin_lock_irqsave(&channel->vc.lock, flags);
 
        rz_lmdesc_setup(channel, channel->lmdesc.base);
 
-       rz_dmac_disable_hw(channel);
+       /*  Skip touching HW if RPM resume failed. Let the cleanup do its jobs. */
+       if (!ret)
+               rz_dmac_disable_hw(channel);
 
        if (channel->mid_rid >= 0) {
                clear_bit(channel->mid_rid, dmac->modules);
@@ -697,11 +707,22 @@ rz_dmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
 static int rz_dmac_terminate_all(struct dma_chan *chan)
 {
        struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
+       struct rz_dmac *dmac = to_rz_dmac(chan->device);
        unsigned long flags;
        LIST_HEAD(head);
+       int ret;
+
+       PM_RUNTIME_ACQUIRE_IF_ENABLED(dmac->dev, pm);
+       ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+       if (ret) {
+               dev_err(dmac->dev, "RPM resume failed for channel %s, ret=%d\n!",
+                       dma_chan_name(chan), ret);
+       }
 
        spin_lock_irqsave(&channel->vc.lock, flags);
-       rz_dmac_disable_hw(channel);
+       /* Don't return if RPM failed. Let the cleanup do its jobs. */
+       if (!ret)
+               rz_dmac_disable_hw(channel);
        rz_lmdesc_setup(channel, channel->lmdesc.base);
 
        if (channel->desc) {
@@ -716,13 +737,20 @@ static int rz_dmac_terminate_all(struct dma_chan *chan)
        spin_unlock_irqrestore(&channel->vc.lock, flags);
        vchan_dma_desc_free_list(&channel->vc, &head);
 
-       return 0;
+       return ret;
 }
 
 static void rz_dmac_issue_pending(struct dma_chan *chan)
 {
        struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
+       struct rz_dmac *dmac = to_rz_dmac(chan->device);
        unsigned long flags;
+       int ret;
+
+       PM_RUNTIME_ACQUIRE_IF_ENABLED(dmac->dev, pm);
+       ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+       if (ret)
+               return;
 
        spin_lock_irqsave(&channel->vc.lock, flags);
 
@@ -807,6 +835,11 @@ static void rz_dmac_device_synchronize(struct dma_chan *chan)
 
        vchan_synchronize(&channel->vc);
 
+       PM_RUNTIME_ACQUIRE_IF_ENABLED(dmac->dev, pm);
+       ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+       if (ret)
+               return;
+
        ret = read_poll_timeout(rz_dmac_ch_readl, chstat, !(chstat & CHSTAT_EN),
                                100, 100000, false, channel, CHSTAT, 1);
        if (ret < 0)
@@ -866,6 +899,7 @@ static int rz_dmac_chan_get_residue(struct device *dev, struct rz_dmac_chan *cha
        struct rz_dmac_desc *desc = NULL;
        struct virt_dma_desc *vd;
        u32 crla, crtb, i;
+       int ret;
 
        vd = vchan_find_desc(&channel->vc, cookie);
        if (vd) {
@@ -884,6 +918,11 @@ static int rz_dmac_chan_get_residue(struct device *dev, struct rz_dmac_chan *cha
                return 0;
        }
 
+       PM_RUNTIME_ACQUIRE_IF_ENABLED(dev, pm);
+       ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+       if (ret)
+               return ret;
+
        /*
         * We need to read two registers. Make sure the hardware does not move
         * to next lmdesc while reading the current lmdesc. Trying it 3 times
@@ -965,6 +1004,13 @@ set_bit:
 static int rz_dmac_device_pause(struct dma_chan *chan)
 {
        struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
+       struct rz_dmac *dmac = to_rz_dmac(chan->device);
+       int ret;
+
+       PM_RUNTIME_ACQUIRE_IF_ENABLED(dmac->dev, pm);
+       ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+       if (ret)
+               return ret;
 
        guard(spinlock_irqsave)(&channel->vc.lock);
 
@@ -994,6 +1040,13 @@ static int rz_dmac_device_resume_set(struct rz_dmac_chan *channel,
 static int rz_dmac_device_resume(struct dma_chan *chan)
 {
        struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
+       struct rz_dmac *dmac = to_rz_dmac(chan->device);
+       int ret;
+
+       PM_RUNTIME_ACQUIRE_IF_ENABLED(dmac->dev, pm);
+       ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+       if (ret)
+               return ret;
 
        guard(spinlock_irqsave)(&channel->vc.lock);
 
@@ -1274,6 +1327,7 @@ static int rz_dmac_probe(struct platform_device *pdev)
                return dev_err_probe(&pdev->dev, PTR_ERR(dmac->rstc),
                                     "failed to get resets\n");
 
+       pm_runtime_irq_safe(&pdev->dev);
        pm_runtime_enable(&pdev->dev);
        ret = pm_runtime_resume_and_get(&pdev->dev);
        if (ret < 0) {