firewire: ohci: use common buffer for self IDs and AR descriptors

The buffers used for the selfIDs packets and the AR request and response
descriptors end up using three pages because dma_alloc_coherent()
allocates at least one page per call.  However, these data structures
would all fit into 4 KB, so we can save space by using a common buffer
for them.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 34 insertions, 32 deletions

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 01b3bc9154a6..eb7b591e1c1b 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -193,6 +193,9 @@ struct fw_ohci {
 
         struct mutex phy_reg_mutex;
 
+        void *misc_buffer;
+        dma_addr_t misc_buffer_bus;
+
         struct ar_context ar_request_ctx;
         struct ar_context ar_response_ctx;
         struct context at_request_ctx;
@@ -623,11 +626,6 @@ static void ar_context_release(struct ar_context *ctx)
 {
         unsigned int i;
 
-        if (ctx->descriptors)
-                dma_free_coherent(ctx->ohci->card.device,
-                                  AR_BUFFERS * sizeof(struct descriptor),
-                                  ctx->descriptors, ctx->descriptors_bus);
-
         if (ctx->buffer)
                 vm_unmap_ram(ctx->buffer, AR_BUFFERS + AR_WRAPAROUND_PAGES);
 
@@ -925,8 +923,8 @@ error:
         ctx->pointer = NULL;
 }
 
-static int ar_context_init(struct ar_context *ctx,
-                           struct fw_ohci *ohci, u32 regs)
+static int ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci,
+                           unsigned int descriptors_offset, u32 regs)
 {
         unsigned int i;
         dma_addr_t dma_addr;
@@ -960,13 +958,8 @@ static int ar_context_init(struct ar_context *ctx,
         if (!ctx->buffer)
                 goto out_of_memory;
 
-        ctx->descriptors =
-                dma_alloc_coherent(ohci->card.device,
-                                   AR_BUFFERS * sizeof(struct descriptor),
-                                   &ctx->descriptors_bus,
-                                   GFP_KERNEL);
-        if (!ctx->descriptors)
-                goto out_of_memory;
+        ctx->descriptors     = ohci->misc_buffer     + descriptors_offset;
+        ctx->descriptors_bus = ohci->misc_buffer_bus + descriptors_offset;
 
         for (i = 0; i < AR_BUFFERS; i++) {
                 d = &ctx->descriptors[i];
@@ -3108,12 +3101,28 @@ static int __devinit pci_probe(struct pci_dev *dev,
         if (param_quirks)
                 ohci->quirks = param_quirks;
 
-        err = ar_context_init(&ohci->ar_request_ctx, ohci,
+        /*
+         * Because dma_alloc_coherent() allocates at least one page,
+         * we save space by using a common buffer for the AR request/
+         * response descriptors and the self IDs buffer.
+         */
+        BUILD_BUG_ON(AR_BUFFERS * sizeof(struct descriptor) > PAGE_SIZE/4);
+        BUILD_BUG_ON(SELF_ID_BUF_SIZE > PAGE_SIZE/2);
+        ohci->misc_buffer = dma_alloc_coherent(ohci->card.device,
+                                               PAGE_SIZE,
+                                               &ohci->misc_buffer_bus,
+                                               GFP_KERNEL);
+        if (!ohci->misc_buffer) {
+                err = -ENOMEM;
+                goto fail_iounmap;
+        }
+
+        err = ar_context_init(&ohci->ar_request_ctx, ohci, 0,
                               OHCI1394_AsReqRcvContextControlSet);
         if (err < 0)
-                goto fail_iounmap;
+                goto fail_misc_buf;
 
-        err = ar_context_init(&ohci->ar_response_ctx, ohci,
+        err = ar_context_init(&ohci->ar_response_ctx, ohci, PAGE_SIZE/4,
                               OHCI1394_AsRspRcvContextControlSet);
         if (err < 0)
                 goto fail_arreq_ctx;
@@ -3148,15 +3157,8 @@ static int __devinit pci_probe(struct pci_dev *dev,
                 goto fail_contexts;
         }
 
-        /* self-id dma buffer allocation */
-        ohci->self_id_cpu = dma_alloc_coherent(ohci->card.device,
-                                               SELF_ID_BUF_SIZE,
-                                               &ohci->self_id_bus,
-                                               GFP_KERNEL);
-        if (ohci->self_id_cpu == NULL) {
-                err = -ENOMEM;
-                goto fail_contexts;
-        }
+        ohci->self_id_cpu = ohci->misc_buffer     + PAGE_SIZE/2;
+        ohci->self_id_bus = ohci->misc_buffer_bus + PAGE_SIZE/2;
 
         bus_options = reg_read(ohci, OHCI1394_BusOptions);
         max_receive = (bus_options >> 12) & 0xf;
@@ -3166,7 +3168,7 @@ static int __devinit pci_probe(struct pci_dev *dev,
 
         err = fw_card_add(&ohci->card, max_receive, link_speed, guid);
         if (err)
-                goto fail_self_id;
+                goto fail_contexts;
 
         version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;
         fw_notify("Added fw-ohci device %s, OHCI v%x.%x, "
@@ -3176,9 +3178,6 @@ static int __devinit pci_probe(struct pci_dev *dev,
 
         return 0;
 
- fail_self_id:
-        dma_free_coherent(ohci->card.device, SELF_ID_BUF_SIZE,
-                          ohci->self_id_cpu, ohci->self_id_bus);
  fail_contexts:
         kfree(ohci->ir_context_list);
         kfree(ohci->it_context_list);
@@ -3189,6 +3188,9 @@ static int __devinit pci_probe(struct pci_dev *dev,
         ar_context_release(&ohci->ar_response_ctx);
  fail_arreq_ctx:
         ar_context_release(&ohci->ar_request_ctx);
+ fail_misc_buf:
+        dma_free_coherent(ohci->card.device, PAGE_SIZE,
+                          ohci->misc_buffer, ohci->misc_buffer_bus);
  fail_iounmap:
         pci_iounmap(dev, ohci->registers);
  fail_iomem:
@@ -3228,10 +3230,10 @@ static void pci_remove(struct pci_dev *dev)
         if (ohci->config_rom)
                 dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
                                   ohci->config_rom, ohci->config_rom_bus);
-        dma_free_coherent(ohci->card.device, SELF_ID_BUF_SIZE,
-                          ohci->self_id_cpu, ohci->self_id_bus);
         ar_context_release(&ohci->ar_request_ctx);
         ar_context_release(&ohci->ar_response_ctx);
+        dma_free_coherent(ohci->card.device, PAGE_SIZE,
+                          ohci->misc_buffer, ohci->misc_buffer_bus);
         context_release(&ohci->at_request_ctx);
         context_release(&ohci->at_response_ctx);
         kfree(ohci->it_context_list);