1d9f3216bSAdrian Bunk /* 21da177e4SLinus Torvalds * linux/kernel/dma.c: A DMA channel allocator. Inspired by linux/kernel/irq.c. 31da177e4SLinus Torvalds * 41da177e4SLinus Torvalds * Written by Hennus Bergman, 1992. 51da177e4SLinus Torvalds * 61da177e4SLinus Torvalds * 1994/12/26: Changes by Alex Nash to fix a minor bug in /proc/dma. 71da177e4SLinus Torvalds * In the previous version the reported device could end up being wrong, 81da177e4SLinus Torvalds * if a device requested a DMA channel that was already in use. 91da177e4SLinus Torvalds * [It also happened to remove the sizeof(char *) == sizeof(int) 101da177e4SLinus Torvalds * assumption introduced because of those /proc/dma patches. -- Hennus] 111da177e4SLinus Torvalds */ 12*9984de1aSPaul Gortmaker #include <linux/export.h> 131da177e4SLinus Torvalds #include <linux/kernel.h> 141da177e4SLinus Torvalds #include <linux/errno.h> 151da177e4SLinus Torvalds #include <linux/spinlock.h> 161da177e4SLinus Torvalds #include <linux/string.h> 171da177e4SLinus Torvalds #include <linux/seq_file.h> 181da177e4SLinus Torvalds #include <linux/proc_fs.h> 191da177e4SLinus Torvalds #include <linux/init.h> 201da177e4SLinus Torvalds #include <asm/dma.h> 211da177e4SLinus Torvalds #include <asm/system.h> 221da177e4SLinus Torvalds 231da177e4SLinus Torvalds 241da177e4SLinus Torvalds 251da177e4SLinus Torvalds /* A note on resource allocation: 261da177e4SLinus Torvalds * 271da177e4SLinus Torvalds * All drivers needing DMA channels, should allocate and release them 281da177e4SLinus Torvalds * through the public routines `request_dma()' and `free_dma()'. 291da177e4SLinus Torvalds * 301da177e4SLinus Torvalds * In order to avoid problems, all processes should allocate resources in 311da177e4SLinus Torvalds * the same sequence and release them in the reverse order. 321da177e4SLinus Torvalds * 331da177e4SLinus Torvalds * So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA. 341da177e4SLinus Torvalds * When releasing them, first release the DMA, then release the IRQ. 351da177e4SLinus Torvalds * If you don't, you may cause allocation requests to fail unnecessarily. 361da177e4SLinus Torvalds * This doesn't really matter now, but it will once we get real semaphores 371da177e4SLinus Torvalds * in the kernel. 381da177e4SLinus Torvalds */ 391da177e4SLinus Torvalds 401da177e4SLinus Torvalds 411da177e4SLinus Torvalds DEFINE_SPINLOCK(dma_spin_lock); 421da177e4SLinus Torvalds 431da177e4SLinus Torvalds /* 441da177e4SLinus Torvalds * If our port doesn't define this it has no PC like DMA 451da177e4SLinus Torvalds */ 461da177e4SLinus Torvalds 471da177e4SLinus Torvalds #ifdef MAX_DMA_CHANNELS 481da177e4SLinus Torvalds 491da177e4SLinus Torvalds 501da177e4SLinus Torvalds /* Channel n is busy iff dma_chan_busy[n].lock != 0. 511da177e4SLinus Torvalds * DMA0 used to be reserved for DRAM refresh, but apparently not any more... 521da177e4SLinus Torvalds * DMA4 is reserved for cascading. 531da177e4SLinus Torvalds */ 541da177e4SLinus Torvalds 551da177e4SLinus Torvalds struct dma_chan { 561da177e4SLinus Torvalds int lock; 571da177e4SLinus Torvalds const char *device_id; 581da177e4SLinus Torvalds }; 591da177e4SLinus Torvalds 601da177e4SLinus Torvalds static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = { 611da177e4SLinus Torvalds [4] = { 1, "cascade" }, 621da177e4SLinus Torvalds }; 631da177e4SLinus Torvalds 641da177e4SLinus Torvalds 65eed34d0fSRandy Dunlap /** 66eed34d0fSRandy Dunlap * request_dma - request and reserve a system DMA channel 67eed34d0fSRandy Dunlap * @dmanr: DMA channel number 68eed34d0fSRandy Dunlap * @device_id: reserving device ID string, used in /proc/dma 69eed34d0fSRandy Dunlap */ 701da177e4SLinus Torvalds int request_dma(unsigned int dmanr, const char * device_id) 711da177e4SLinus Torvalds { 721da177e4SLinus Torvalds if (dmanr >= MAX_DMA_CHANNELS) 731da177e4SLinus Torvalds return -EINVAL; 741da177e4SLinus Torvalds 751da177e4SLinus Torvalds if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0) 761da177e4SLinus Torvalds return -EBUSY; 771da177e4SLinus Torvalds 781da177e4SLinus Torvalds dma_chan_busy[dmanr].device_id = device_id; 791da177e4SLinus Torvalds 801da177e4SLinus Torvalds /* old flag was 0, now contains 1 to indicate busy */ 811da177e4SLinus Torvalds return 0; 821da177e4SLinus Torvalds } /* request_dma */ 831da177e4SLinus Torvalds 84eed34d0fSRandy Dunlap /** 85eed34d0fSRandy Dunlap * free_dma - free a reserved system DMA channel 86eed34d0fSRandy Dunlap * @dmanr: DMA channel number 87eed34d0fSRandy Dunlap */ 881da177e4SLinus Torvalds void free_dma(unsigned int dmanr) 891da177e4SLinus Torvalds { 901da177e4SLinus Torvalds if (dmanr >= MAX_DMA_CHANNELS) { 911da177e4SLinus Torvalds printk(KERN_WARNING "Trying to free DMA%d\n", dmanr); 921da177e4SLinus Torvalds return; 931da177e4SLinus Torvalds } 941da177e4SLinus Torvalds 951da177e4SLinus Torvalds if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) { 961da177e4SLinus Torvalds printk(KERN_WARNING "Trying to free free DMA%d\n", dmanr); 971da177e4SLinus Torvalds return; 981da177e4SLinus Torvalds } 991da177e4SLinus Torvalds 1001da177e4SLinus Torvalds } /* free_dma */ 1011da177e4SLinus Torvalds 1021da177e4SLinus Torvalds #else 1031da177e4SLinus Torvalds 1041da177e4SLinus Torvalds int request_dma(unsigned int dmanr, const char *device_id) 1051da177e4SLinus Torvalds { 1061da177e4SLinus Torvalds return -EINVAL; 1071da177e4SLinus Torvalds } 1081da177e4SLinus Torvalds 1091da177e4SLinus Torvalds void free_dma(unsigned int dmanr) 1101da177e4SLinus Torvalds { 1111da177e4SLinus Torvalds } 1121da177e4SLinus Torvalds 1131da177e4SLinus Torvalds #endif 1141da177e4SLinus Torvalds 1151da177e4SLinus Torvalds #ifdef CONFIG_PROC_FS 1161da177e4SLinus Torvalds 1171da177e4SLinus Torvalds #ifdef MAX_DMA_CHANNELS 1181da177e4SLinus Torvalds static int proc_dma_show(struct seq_file *m, void *v) 1191da177e4SLinus Torvalds { 1201da177e4SLinus Torvalds int i; 1211da177e4SLinus Torvalds 1221da177e4SLinus Torvalds for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) { 1231da177e4SLinus Torvalds if (dma_chan_busy[i].lock) { 1241da177e4SLinus Torvalds seq_printf(m, "%2d: %s\n", i, 1251da177e4SLinus Torvalds dma_chan_busy[i].device_id); 1261da177e4SLinus Torvalds } 1271da177e4SLinus Torvalds } 1281da177e4SLinus Torvalds return 0; 1291da177e4SLinus Torvalds } 1301da177e4SLinus Torvalds #else 1311da177e4SLinus Torvalds static int proc_dma_show(struct seq_file *m, void *v) 1321da177e4SLinus Torvalds { 1331da177e4SLinus Torvalds seq_puts(m, "No DMA\n"); 1341da177e4SLinus Torvalds return 0; 1351da177e4SLinus Torvalds } 1361da177e4SLinus Torvalds #endif /* MAX_DMA_CHANNELS */ 1371da177e4SLinus Torvalds 1381da177e4SLinus Torvalds static int proc_dma_open(struct inode *inode, struct file *file) 1391da177e4SLinus Torvalds { 1401da177e4SLinus Torvalds return single_open(file, proc_dma_show, NULL); 1411da177e4SLinus Torvalds } 1421da177e4SLinus Torvalds 14315ad7cdcSHelge Deller static const struct file_operations proc_dma_operations = { 1441da177e4SLinus Torvalds .open = proc_dma_open, 1451da177e4SLinus Torvalds .read = seq_read, 1461da177e4SLinus Torvalds .llseek = seq_lseek, 1471da177e4SLinus Torvalds .release = single_release, 1481da177e4SLinus Torvalds }; 1491da177e4SLinus Torvalds 1501da177e4SLinus Torvalds static int __init proc_dma_init(void) 1511da177e4SLinus Torvalds { 152c33fff0aSDenis V. Lunev proc_create("dma", 0, NULL, &proc_dma_operations); 1531da177e4SLinus Torvalds return 0; 1541da177e4SLinus Torvalds } 1551da177e4SLinus Torvalds 1561da177e4SLinus Torvalds __initcall(proc_dma_init); 1571da177e4SLinus Torvalds #endif 1581da177e4SLinus Torvalds 1591da177e4SLinus Torvalds EXPORT_SYMBOL(request_dma); 1601da177e4SLinus Torvalds EXPORT_SYMBOL(free_dma); 1611da177e4SLinus Torvalds EXPORT_SYMBOL(dma_spin_lock); 162