firewire: octlet AT payloads can be stack-allocated
authorStefan Richter <stefanr@s5r6.in-berlin.de>
Fri, 22 Apr 2011 13:13:54 +0000 (15:13 +0200)
committerStefan Richter <stefanr@s5r6.in-berlin.de>
Tue, 10 May 2011 20:53:44 +0000 (22:53 +0200)
We do not need slab allocations anymore in order to satisfy
streaming DMA mapping constraints, thanks to commit da28947e7e36
"firewire: ohci: avoid separate DMA mapping for small AT payloads".

(Besides, the slab-allocated buffers that firewire-core, firewire-sbp2,
and firedtv used to provide for 8-byte write and lock requests were
still not fully portable since they crossed cacheline boundaries or
shared a cacheline with unrelated CPU-accessed data.  snd-firewire-lib
got this aspect right by using an extra kmalloc/ kfree just for the
8-byte transaction buffer.)

This change replaces kmalloc'ed lock transaction scratch buffers in
firewire-core, firedtv, and snd-firewire-lib by local stack allocations.
Perhaps the most notable result of the change is simpler locking because
there is no need to serialize usages of preallocated per-device buffers
anymore.  Also, allocations and deallocations are simpler.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
drivers/firewire/core-card.c
drivers/firewire/core-cdev.c
drivers/firewire/core-iso.c
drivers/firewire/core-transaction.c
drivers/media/dvb/firewire/firedtv-avc.c
include/linux/firewire.h
sound/firewire/cmp.c
sound/firewire/iso-resources.c
sound/firewire/iso-resources.h

index 3c44fbc..e119f1e 100644 (file)
@@ -258,8 +258,7 @@ static void allocate_broadcast_channel(struct fw_card *card, int generation)
 
        if (!card->broadcast_channel_allocated) {
                fw_iso_resource_manage(card, generation, 1ULL << 31,
-                                      &channel, &bandwidth, true,
-                                      card->bm_transaction_data);
+                                      &channel, &bandwidth, true);
                if (channel != 31) {
                        fw_notify("failed to allocate broadcast channel\n");
                        return;
@@ -294,6 +293,7 @@ static void bm_work(struct work_struct *work)
        bool root_device_is_cmc;
        bool irm_is_1394_1995_only;
        bool keep_this_irm;
+       __be32 transaction_data[2];
 
        spin_lock_irq(&card->lock);
 
@@ -355,21 +355,21 @@ static void bm_work(struct work_struct *work)
                        goto pick_me;
                }
 
-               card->bm_transaction_data[0] = cpu_to_be32(0x3f);
-               card->bm_transaction_data[1] = cpu_to_be32(local_id);
+               transaction_data[0] = cpu_to_be32(0x3f);
+               transaction_data[1] = cpu_to_be32(local_id);
 
                spin_unlock_irq(&card->lock);
 
                rcode = fw_run_transaction(card, TCODE_LOCK_COMPARE_SWAP,
                                irm_id, generation, SCODE_100,
                                CSR_REGISTER_BASE + CSR_BUS_MANAGER_ID,
-                               card->bm_transaction_data, 8);
+                               transaction_data, 8);
 
                if (rcode == RCODE_GENERATION)
                        /* Another bus reset, BM work has been rescheduled. */
                        goto out;
 
-               bm_id = be32_to_cpu(card->bm_transaction_data[0]);
+               bm_id = be32_to_cpu(transaction_data[0]);
 
                spin_lock_irq(&card->lock);
                if (rcode == RCODE_COMPLETE && generation == card->generation)
@@ -490,11 +490,11 @@ static void bm_work(struct work_struct *work)
                /*
                 * Make sure that the cycle master sends cycle start packets.
                 */
-               card->bm_transaction_data[0] = cpu_to_be32(CSR_STATE_BIT_CMSTR);
+               transaction_data[0] = cpu_to_be32(CSR_STATE_BIT_CMSTR);
                rcode = fw_run_transaction(card, TCODE_WRITE_QUADLET_REQUEST,
                                root_id, generation, SCODE_100,
                                CSR_REGISTER_BASE + CSR_STATE_SET,
-                               card->bm_transaction_data, 4);
+                               transaction_data, 4);
                if (rcode == RCODE_GENERATION)
                        goto out;
        }
index 62ac111..2a3f1c4 100644 (file)
@@ -141,7 +141,6 @@ struct iso_resource {
        int generation;
        u64 channels;
        s32 bandwidth;
-       __be32 transaction_data[2];
        struct iso_resource_event *e_alloc, *e_dealloc;
 };
 
@@ -1229,8 +1228,7 @@ static void iso_resource_work(struct work_struct *work)
                        r->channels, &channel, &bandwidth,
                        todo == ISO_RES_ALLOC ||
                        todo == ISO_RES_REALLOC ||
-                       todo == ISO_RES_ALLOC_ONCE,
-                       r->transaction_data);
+                       todo == ISO_RES_ALLOC_ONCE);
        /*
         * Is this generation outdated already?  As long as this resource sticks
         * in the idr, it will be scheduled again for a newer generation or at
index 481056d..f872ede 100644 (file)
@@ -196,9 +196,10 @@ EXPORT_SYMBOL(fw_iso_context_stop);
  */
 
 static int manage_bandwidth(struct fw_card *card, int irm_id, int generation,
-                           int bandwidth, bool allocate, __be32 data[2])
+                           int bandwidth, bool allocate)
 {
        int try, new, old = allocate ? BANDWIDTH_AVAILABLE_INITIAL : 0;
+       __be32 data[2];
 
        /*
         * On a 1394a IRM with low contention, try < 1 is enough.
@@ -233,9 +234,10 @@ static int manage_bandwidth(struct fw_card *card, int irm_id, int generation,
 }
 
 static int manage_channel(struct fw_card *card, int irm_id, int generation,
-               u32 channels_mask, u64 offset, bool allocate, __be32 data[2])
+               u32 channels_mask, u64 offset, bool allocate)
 {
        __be32 bit, all, old;
+       __be32 data[2];
        int channel, ret = -EIO, retry = 5;
 
        old = all = allocate ? cpu_to_be32(~0) : 0;
@@ -284,7 +286,7 @@ static int manage_channel(struct fw_card *card, int irm_id, int generation,
 }
 
 static void deallocate_channel(struct fw_card *card, int irm_id,
-                              int generation, int channel, __be32 buffer[2])
+                              int generation, int channel)
 {
        u32 mask;
        u64 offset;
@@ -293,7 +295,7 @@ static void deallocate_channel(struct fw_card *card, int irm_id,
        offset = channel < 32 ? CSR_REGISTER_BASE + CSR_CHANNELS_AVAILABLE_HI :
                                CSR_REGISTER_BASE + CSR_CHANNELS_AVAILABLE_LO;
 
-       manage_channel(card, irm_id, generation, mask, offset, false, buffer);
+       manage_channel(card, irm_id, generation, mask, offset, false);
 }
 
 /**
@@ -322,7 +324,7 @@ static void deallocate_channel(struct fw_card *card, int irm_id,
  */
 void fw_iso_resource_manage(struct fw_card *card, int generation,
                            u64 channels_mask, int *channel, int *bandwidth,
-                           bool allocate, __be32 buffer[2])
+                           bool allocate)
 {
        u32 channels_hi = channels_mask;        /* channels 31...0 */
        u32 channels_lo = channels_mask >> 32;  /* channels 63...32 */
@@ -335,11 +337,11 @@ void fw_iso_resource_manage(struct fw_card *card, int generation,
        if (channels_hi)
                c = manage_channel(card, irm_id, generation, channels_hi,
                                CSR_REGISTER_BASE + CSR_CHANNELS_AVAILABLE_HI,
-                               allocate, buffer);
+                               allocate);
        if (channels_lo && c < 0) {
                c = manage_channel(card, irm_id, generation, channels_lo,
                                CSR_REGISTER_BASE + CSR_CHANNELS_AVAILABLE_LO,
-                               allocate, buffer);
+                               allocate);
                if (c >= 0)
                        c += 32;
        }
@@ -351,14 +353,13 @@ void fw_iso_resource_manage(struct fw_card *card, int generation,
        if (*bandwidth == 0)
                return;
 
-       ret = manage_bandwidth(card, irm_id, generation, *bandwidth,
-                              allocate, buffer);
+       ret = manage_bandwidth(card, irm_id, generation, *bandwidth, allocate);
        if (ret < 0)
                *bandwidth = 0;
 
        if (allocate && ret < 0) {
                if (c >= 0)
-                       deallocate_channel(card, irm_id, generation, c, buffer);
+                       deallocate_channel(card, irm_id, generation, c);
                *channel = ret;
        }
 }
index d00f8ce..77275fd 100644 (file)
@@ -326,8 +326,8 @@ static int allocate_tlabel(struct fw_card *card)
  * It will contain tag, channel, and sy data instead of a node ID then.
  *
  * The payload buffer at @data is going to be DMA-mapped except in case of
- * quadlet-sized payload or of local (loopback) requests.  Hence make sure that
- * the buffer complies with the restrictions for DMA-mapped memory.  The
+ * @length <= 8 or of local (loopback) requests.  Hence make sure that the
+ * buffer complies with the restrictions of the streaming DMA mapping API.
  * @payload must not be freed before the @callback is called.
  *
  * In case of request types without payload, @data is NULL and @length is 0.
@@ -411,7 +411,8 @@ static void transaction_callback(struct fw_card *card, int rcode,
  *
  * Returns the RCODE.  See fw_send_request() for parameter documentation.
  * Unlike fw_send_request(), @data points to the payload of the request or/and
- * to the payload of the response.
+ * to the payload of the response.  DMA mapping restrictions apply to outbound
+ * request payloads of >= 8 bytes but not to inbound response payloads.
  */
 int fw_run_transaction(struct fw_card *card, int tcode, int destination_id,
                       int generation, int speed, unsigned long long offset,
index fc5ccd8..21c52e3 100644 (file)
@@ -1320,14 +1320,10 @@ static int cmp_read(struct firedtv *fdtv, u64 addr, __be32 *data)
 {
        int ret;
 
-       mutex_lock(&fdtv->avc_mutex);
-
        ret = fdtv_read(fdtv, addr, data);
        if (ret < 0)
                dev_err(fdtv->device, "CMP: read I/O error\n");
 
-       mutex_unlock(&fdtv->avc_mutex);
-
        return ret;
 }
 
@@ -1335,18 +1331,9 @@ static int cmp_lock(struct firedtv *fdtv, u64 addr, __be32 data[])
 {
        int ret;
 
-       mutex_lock(&fdtv->avc_mutex);
-
-       /* data[] is stack-allocated and should not be DMA-mapped. */
-       memcpy(fdtv->avc_data, data, 8);
-
-       ret = fdtv_lock(fdtv, addr, fdtv->avc_data);
+       ret = fdtv_lock(fdtv, addr, data);
        if (ret < 0)
                dev_err(fdtv->device, "CMP: lock I/O error\n");
-       else
-               memcpy(data, fdtv->avc_data, 8);
-
-       mutex_unlock(&fdtv->avc_mutex);
 
        return ret;
 }
index c64f368..de90e1f 100644 (file)
@@ -125,7 +125,6 @@ struct fw_card {
        struct delayed_work bm_work; /* bus manager job */
        int bm_retries;
        int bm_generation;
-       __be32 bm_transaction_data[2];
        int bm_node_id;
        bool bm_abdicate;
 
@@ -447,6 +446,6 @@ int fw_iso_context_stop(struct fw_iso_context *ctx);
 void fw_iso_context_destroy(struct fw_iso_context *ctx);
 void fw_iso_resource_manage(struct fw_card *card, int generation,
                            u64 channels_mask, int *channel, int *bandwidth,
-                           bool allocate, __be32 buffer[2]);
+                           bool allocate);
 
 #endif /* _LINUX_FIREWIRE_H */
index 4a37f3a..14cacbc 100644 (file)
@@ -49,10 +49,9 @@ static int pcr_modify(struct cmp_connection *c,
                      enum bus_reset_handling bus_reset_handling)
 {
        struct fw_device *device = fw_parent_device(c->resources.unit);
-       __be32 *buffer = c->resources.buffer;
        int generation = c->resources.generation;
        int rcode, errors = 0;
-       __be32 old_arg;
+       __be32 old_arg, buffer[2];
        int err;
 
        buffer[0] = c->last_pcr_value;
index 775dbd5..bb9c0c1 100644 (file)
@@ -11,7 +11,6 @@
 #include <linux/jiffies.h>
 #include <linux/mutex.h>
 #include <linux/sched.h>
-#include <linux/slab.h>
 #include <linux/spinlock.h>
 #include "iso-resources.h"
 
  */
 int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit)
 {
-       r->buffer = kmalloc(2 * 4, GFP_KERNEL);
-       if (!r->buffer)
-               return -ENOMEM;
-
        r->channels_mask = ~0uLL;
        r->unit = fw_unit_get(unit);
        mutex_init(&r->mutex);
@@ -44,7 +39,6 @@ int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit)
 void fw_iso_resources_destroy(struct fw_iso_resources *r)
 {
        WARN_ON(r->allocated);
-       kfree(r->buffer);
        mutex_destroy(&r->mutex);
        fw_unit_put(r->unit);
 }
@@ -131,7 +125,7 @@ retry_after_bus_reset:
 
        bandwidth = r->bandwidth + r->bandwidth_overhead;
        fw_iso_resource_manage(card, r->generation, r->channels_mask,
-                              &channel, &bandwidth, true, r->buffer);
+                              &channel, &bandwidth, true);
        if (channel == -EAGAIN) {
                mutex_unlock(&r->mutex);
                goto retry_after_bus_reset;
@@ -184,7 +178,7 @@ int fw_iso_resources_update(struct fw_iso_resources *r)
        bandwidth = r->bandwidth + r->bandwidth_overhead;
 
        fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
-                              &channel, &bandwidth, true, r->buffer);
+                              &channel, &bandwidth, true);
        /*
         * When another bus reset happens, pretend that the allocation
         * succeeded; we will try again for the new generation later.
@@ -220,7 +214,7 @@ void fw_iso_resources_free(struct fw_iso_resources *r)
        if (r->allocated) {
                bandwidth = r->bandwidth + r->bandwidth_overhead;
                fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
-                                      &channel, &bandwidth, false, r->buffer);
+                                      &channel, &bandwidth, false);
                if (channel < 0)
                        dev_err(&r->unit->device,
                                "isochronous resource deallocation failed\n");
index 3f0730e..5a9af7c 100644 (file)
@@ -24,7 +24,6 @@ struct fw_iso_resources {
        unsigned int bandwidth_overhead;
        int generation; /* in which allocation is valid */
        bool allocated;
-       __be32 *buffer;
 };
 
 int fw_iso_resources_init(struct fw_iso_resources *r,