dmaengine: shdma: use normal interface for passing slave id

in dma_slave_config, which is incompatible with the way that the
dmaengine API normally works.

I've had a closer look at the existing code now and found that all
slave drivers that pass a slave_id in dma_slave_config for SH do that
right after passing the same ID into shdma_chan_filter, so we can just
rely on that. However, the various shdma drivers currently do not
remember the slave ID that was passed into the filter function when
used in non-DT mode and only check the value to find a matching channel,
unlike all other drivers.

There might still be drivers that are not part of the kernel that rely
on setting the slave_id to some other value, so to be on the safe side,
this adds another 'real_slave_id' field to shdma_chan that remembers
the ID and uses it when a driver passes a zero slave_id in dma_slave_config,
like most drivers do.

Eventually, the real_slave_id and slave_id fields should just get merged
into one field, but that requires other changes.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

2 files changed, 54 insertions, 20 deletions

diff --git a/drivers/dma/sh/shdma-base.c b/drivers/dma/sh/shdma-base.c
index 8ee383d339a5..10fcabad80f3 100644
--- a/drivers/dma/sh/shdma-base.c
+++ b/drivers/dma/sh/shdma-base.c
@@ -171,8 +171,7 @@ static struct shdma_desc *shdma_get_desc(struct shdma_chan *schan)
         return NULL;
 }
 
-static int shdma_setup_slave(struct shdma_chan *schan, int slave_id,
-                             dma_addr_t slave_addr)
+static int shdma_setup_slave(struct shdma_chan *schan, dma_addr_t slave_addr)
 {
         struct shdma_dev *sdev = to_shdma_dev(schan->dma_chan.device);
         const struct shdma_ops *ops = sdev->ops;
@@ -183,25 +182,23 @@ static int shdma_setup_slave(struct shdma_chan *schan, int slave_id,
                 ret = ops->set_slave(schan, match, slave_addr, true);
                 if (ret < 0)
                         return ret;
-
-                slave_id = schan->slave_id;
         } else {
-                match = slave_id;
+                match = schan->real_slave_id;
         }
 
-        if (slave_id < 0 || slave_id >= slave_num)
+        if (schan->real_slave_id < 0 || schan->real_slave_id >= slave_num)
                 return -EINVAL;
 
-        if (test_and_set_bit(slave_id, shdma_slave_used))
+        if (test_and_set_bit(schan->real_slave_id, shdma_slave_used))
                 return -EBUSY;
 
         ret = ops->set_slave(schan, match, slave_addr, false);
         if (ret < 0) {
-                clear_bit(slave_id, shdma_slave_used);
+                clear_bit(schan->real_slave_id, shdma_slave_used);
                 return ret;
         }
 
-        schan->slave_id = slave_id;
+        schan->slave_id = schan->real_slave_id;
 
         return 0;
 }
@@ -221,10 +218,12 @@ static int shdma_alloc_chan_resources(struct dma_chan *chan)
          */
         if (slave) {
                 /* Legacy mode: .private is set in filter */
-                ret = shdma_setup_slave(schan, slave->slave_id, 0);
+                schan->real_slave_id = slave->slave_id;
+                ret = shdma_setup_slave(schan, 0);
                 if (ret < 0)
                         goto esetslave;
         } else {
+                /* Normal mode: real_slave_id was set by filter */
                 schan->slave_id = -EINVAL;
         }
 
@@ -258,11 +257,14 @@ esetslave:
 
 /*
  * This is the standard shdma filter function to be used as a replacement to the
- * "old" method, using the .private pointer. If for some reason you allocate a
- * channel without slave data, use something like ERR_PTR(-EINVAL) as a filter
+ * "old" method, using the .private pointer.
+ * You always have to pass a valid slave id as the argument, old drivers that
+ * pass ERR_PTR(-EINVAL) as a filter parameter and set it up in dma_slave_config
+ * need to be updated so we can remove the slave_id field from dma_slave_config.
  * parameter. If this filter is used, the slave driver, after calling
  * dma_request_channel(), will also have to call dmaengine_slave_config() with
- * .slave_id, .direction, and either .src_addr or .dst_addr set.
+ * .direction, and either .src_addr or .dst_addr set.
+ *
  * NOTE: this filter doesn't support multiple DMAC drivers with the DMA_SLAVE
  * capability! If this becomes a requirement, hardware glue drivers, using this
  * services would have to provide their own filters, which first would check
@@ -276,7 +278,7 @@ bool shdma_chan_filter(struct dma_chan *chan, void *arg)
 {
         struct shdma_chan *schan;
         struct shdma_dev *sdev;
-        int match = (long)arg;
+        int slave_id = (long)arg;
         int ret;
 
         /* Only support channels handled by this driver. */
@@ -284,19 +286,39 @@ bool shdma_chan_filter(struct dma_chan *chan, void *arg)
             shdma_alloc_chan_resources)
                 return false;
 
-        if (match < 0)
+        schan = to_shdma_chan(chan);
+        sdev = to_shdma_dev(chan->device);
+
+        /*
+         * For DT, the schan->slave_id field is generated by the
+         * set_slave function from the slave ID that is passed in
+         * from xlate. For the non-DT case, the slave ID is
+         * directly passed into the filter function by the driver
+         */
+        if (schan->dev->of_node) {
+                ret = sdev->ops->set_slave(schan, slave_id, 0, true);
+                if (ret < 0)
+                        return false;
+
+                schan->real_slave_id = schan->slave_id;
+                return true;
+        }
+
+        if (slave_id < 0) {
                 /* No slave requested - arbitrary channel */
+                dev_warn(sdev->dma_dev.dev, "invalid slave ID passed to dma_request_slave\n");
                 return true;
+        }
 
-        schan = to_shdma_chan(chan);
-        if (!schan->dev->of_node && match >= slave_num)
+        if (slave_id >= slave_num)
                 return false;
 
-        sdev = to_shdma_dev(schan->dma_chan.device);
-        ret = sdev->ops->set_slave(schan, match, 0, true);
+        ret = sdev->ops->set_slave(schan, slave_id, 0, true);
         if (ret < 0)
                 return false;
 
+        schan->real_slave_id = slave_id;
+
         return true;
 }
 EXPORT_SYMBOL(shdma_chan_filter);
@@ -452,6 +474,8 @@ static void shdma_free_chan_resources(struct dma_chan *chan)
                 chan->private = NULL;
         }
 
+        schan->real_slave_id = 0;
+
         spin_lock_irq(&schan->chan_lock);
 
         list_splice_init(&schan->ld_free, &list);
@@ -764,11 +788,20 @@ static int shdma_config(struct dma_chan *chan,
          */
         if (!config)
                 return -EINVAL;
+
+        /*
+         * overriding the slave_id through dma_slave_config is deprecated,
+         * but possibly some out-of-tree drivers still do it.
+         */
+        if (WARN_ON_ONCE(config->slave_id &&
+                         config->slave_id != schan->real_slave_id))
+                schan->real_slave_id = config->slave_id;
+
         /*
          * We could lock this, but you shouldn't be configuring the
          * channel, while using it...
          */
-        return shdma_setup_slave(schan, config->slave_id,
+        return shdma_setup_slave(schan,
                                  config->direction == DMA_DEV_TO_MEM ?
                                  config->src_addr : config->dst_addr);
 }
diff --git a/include/linux/shdma-base.h b/include/linux/shdma-base.h
index abdf1f229dc3..dd0ba502ccb3 100644
--- a/include/linux/shdma-base.h
+++ b/include/linux/shdma-base.h
@@ -69,6 +69,7 @@ struct shdma_chan {
         int id;                         /* Raw id of this channel */
         int irq;                        /* Channel IRQ */
         int slave_id;                   /* Client ID for slave DMA */
+        int real_slave_id;              /* argument passed to filter function */
         int hw_req;                     /* DMA request line for slave DMA - same
                                          * as MID/RID, used with DT */
         enum shdma_pm_state pm_state;