Automatic merge of rsync://rsync.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6.git/

5 files changed, 162 insertions, 152 deletions

diff --git a/arch/sparc64/kernel/pci_iommu.c b/arch/sparc64/kernel/pci_iommu.c
index 2929834..f009b1b 100644
--- a/arch/sparc64/kernel/pci_iommu.c
+++ b/arch/sparc64/kernel/pci_iommu.c
@@ -8,6 +8,7 @@
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
+#include <linux/delay.h>
 
 #include <asm/pbm.h>
 
@@ -379,6 +380,54 @@ bad:
 	return PCI_DMA_ERROR_CODE;
 }
 
+static void pci_strbuf_flush(struct pci_strbuf *strbuf, struct pci_iommu *iommu, u32 vaddr, unsigned long ctx, unsigned long npages)
+{
+	int limit;
+
+	PCI_STC_FLUSHFLAG_INIT(strbuf);
+	if (strbuf->strbuf_ctxflush &&
+	    iommu->iommu_ctxflush) {
+		unsigned long matchreg, flushreg;
+
+		flushreg = strbuf->strbuf_ctxflush;
+		matchreg = PCI_STC_CTXMATCH_ADDR(strbuf, ctx);
+
+		limit = 10000;
+		do {
+			pci_iommu_write(flushreg, ctx);
+			udelay(10);
+			limit--;
+			if (!limit)
+				break;
+		} while(((long)pci_iommu_read(matchreg)) < 0L);
+		if (!limit)
+			printk(KERN_WARNING "pci_strbuf_flush: ctx flush "
+			       "timeout vaddr[%08x] ctx[%lx]\n",
+			       vaddr, ctx);
+	} else {
+		unsigned long i;
+
+		for (i = 0; i < npages; i++, vaddr += IO_PAGE_SIZE)
+			pci_iommu_write(strbuf->strbuf_pflush, vaddr);
+	}
+
+	pci_iommu_write(strbuf->strbuf_fsync, strbuf->strbuf_flushflag_pa);
+	(void) pci_iommu_read(iommu->write_complete_reg);
+
+	limit = 10000;
+	while (!PCI_STC_FLUSHFLAG_SET(strbuf)) {
+		limit--;
+		if (!limit)
+			break;
+		udelay(10);
+		membar("#LoadLoad");
+	}
+	if (!limit)
+		printk(KERN_WARNING "pci_strbuf_flush: flushflag timeout "
+		       "vaddr[%08x] ctx[%lx] npages[%ld]\n",
+		       vaddr, ctx, npages);
+}
+
 /* Unmap a single streaming mode DMA translation. */
 void pci_unmap_single(struct pci_dev *pdev, dma_addr_t bus_addr, size_t sz, int direction)
 {
@@ -386,7 +435,7 @@ void pci_unmap_single(struct pci_dev *pdev, dma_addr_t bus_addr, size_t sz, int
 	struct pci_iommu *iommu;
 	struct pci_strbuf *strbuf;
 	iopte_t *base;
-	unsigned long flags, npages, i, ctx;
+	unsigned long flags, npages, ctx;
 
 	if (direction == PCI_DMA_NONE)
 		BUG();
@@ -414,29 +463,8 @@ void pci_unmap_single(struct pci_dev *pdev, dma_addr_t bus_addr, size_t sz, int
 		ctx = (iopte_val(*base) & IOPTE_CONTEXT) >> 47UL;
 
 	/* Step 1: Kick data out of streaming buffers if necessary. */
-	if (strbuf->strbuf_enabled) {
-		u32 vaddr = bus_addr;
-
-		PCI_STC_FLUSHFLAG_INIT(strbuf);
-		if (strbuf->strbuf_ctxflush &&
-		    iommu->iommu_ctxflush) {
-			unsigned long matchreg, flushreg;
-
-			flushreg = strbuf->strbuf_ctxflush;
-			matchreg = PCI_STC_CTXMATCH_ADDR(strbuf, ctx);
-			do {
-				pci_iommu_write(flushreg, ctx);
-			} while(((long)pci_iommu_read(matchreg)) < 0L);
-		} else {
-			for (i = 0; i < npages; i++, vaddr += IO_PAGE_SIZE)
-				pci_iommu_write(strbuf->strbuf_pflush, vaddr);
-		}
-
-		pci_iommu_write(strbuf->strbuf_fsync, strbuf->strbuf_flushflag_pa);
-		(void) pci_iommu_read(iommu->write_complete_reg);
-		while (!PCI_STC_FLUSHFLAG_SET(strbuf))
-			membar("#LoadLoad");
-	}
+	if (strbuf->strbuf_enabled)
+		pci_strbuf_flush(strbuf, iommu, bus_addr, ctx, npages);
 
 	/* Step 2: Clear out first TSB entry. */
 	iopte_make_dummy(iommu, base);
@@ -647,29 +675,8 @@ void pci_unmap_sg(struct pci_dev *pdev, struct scatterlist *sglist, int nelems,
 		ctx = (iopte_val(*base) & IOPTE_CONTEXT) >> 47UL;
 
 	/* Step 1: Kick data out of streaming buffers if necessary. */
-	if (strbuf->strbuf_enabled) {
-		u32 vaddr = (u32) bus_addr;
-
-		PCI_STC_FLUSHFLAG_INIT(strbuf);
-		if (strbuf->strbuf_ctxflush &&
-		    iommu->iommu_ctxflush) {
-			unsigned long matchreg, flushreg;
-
-			flushreg = strbuf->strbuf_ctxflush;
-			matchreg = PCI_STC_CTXMATCH_ADDR(strbuf, ctx);
-			do {
-				pci_iommu_write(flushreg, ctx);
-			} while(((long)pci_iommu_read(matchreg)) < 0L);
-		} else {
-			for (i = 0; i < npages; i++, vaddr += IO_PAGE_SIZE)
-				pci_iommu_write(strbuf->strbuf_pflush, vaddr);
-		}
-
-		pci_iommu_write(strbuf->strbuf_fsync, strbuf->strbuf_flushflag_pa);
-		(void) pci_iommu_read(iommu->write_complete_reg);
-		while (!PCI_STC_FLUSHFLAG_SET(strbuf))
-			membar("#LoadLoad");
-	}
+	if (strbuf->strbuf_enabled)
+		pci_strbuf_flush(strbuf, iommu, bus_addr, ctx, npages);
 
 	/* Step 2: Clear out first TSB entry. */
 	iopte_make_dummy(iommu, base);
@@ -715,28 +722,7 @@ void pci_dma_sync_single_for_cpu(struct pci_dev *pdev, dma_addr_t bus_addr, size
 	}
 
 	/* Step 2: Kick data out of streaming buffers. */
-	PCI_STC_FLUSHFLAG_INIT(strbuf);
-	if (iommu->iommu_ctxflush &&
-	    strbuf->strbuf_ctxflush) {
-		unsigned long matchreg, flushreg;
-
-		flushreg = strbuf->strbuf_ctxflush;
-		matchreg = PCI_STC_CTXMATCH_ADDR(strbuf, ctx);
-		do {
-			pci_iommu_write(flushreg, ctx);
-		} while(((long)pci_iommu_read(matchreg)) < 0L);
-	} else {
-		unsigned long i;
-
-		for (i = 0; i < npages; i++, bus_addr += IO_PAGE_SIZE)
-			pci_iommu_write(strbuf->strbuf_pflush, bus_addr);
-	}
-
-	/* Step 3: Perform flush synchronization sequence. */
-	pci_iommu_write(strbuf->strbuf_fsync, strbuf->strbuf_flushflag_pa);
-	(void) pci_iommu_read(iommu->write_complete_reg);
-	while (!PCI_STC_FLUSHFLAG_SET(strbuf))
-		membar("#LoadLoad");
+	pci_strbuf_flush(strbuf, iommu, bus_addr, ctx, npages);
 
 	spin_unlock_irqrestore(&iommu->lock, flags);
 }
@@ -749,7 +735,8 @@ void pci_dma_sync_sg_for_cpu(struct pci_dev *pdev, struct scatterlist *sglist, i
 	struct pcidev_cookie *pcp;
 	struct pci_iommu *iommu;
 	struct pci_strbuf *strbuf;
-	unsigned long flags, ctx;
+	unsigned long flags, ctx, npages, i;
+	u32 bus_addr;
 
 	pcp = pdev->sysdata;
 	iommu = pcp->pbm->iommu;
@@ -772,36 +759,14 @@ void pci_dma_sync_sg_for_cpu(struct pci_dev *pdev, struct scatterlist *sglist, i
 	}
 
 	/* Step 2: Kick data out of streaming buffers. */
-	PCI_STC_FLUSHFLAG_INIT(strbuf);
-	if (iommu->iommu_ctxflush &&
-	    strbuf->strbuf_ctxflush) {
-		unsigned long matchreg, flushreg;
-
-		flushreg = strbuf->strbuf_ctxflush;
-		matchreg = PCI_STC_CTXMATCH_ADDR(strbuf, ctx);
-		do {
-			pci_iommu_write(flushreg, ctx);
-		} while (((long)pci_iommu_read(matchreg)) < 0L);
-	} else {
-		unsigned long i, npages;
-		u32 bus_addr;
-
-		bus_addr = sglist[0].dma_address & IO_PAGE_MASK;
-
-		for(i = 1; i < nelems; i++)
-			if (!sglist[i].dma_length)
-				break;
-		i--;
-		npages = (IO_PAGE_ALIGN(sglist[i].dma_address + sglist[i].dma_length) - bus_addr) >> IO_PAGE_SHIFT;
-		for (i = 0; i < npages; i++, bus_addr += IO_PAGE_SIZE)
-			pci_iommu_write(strbuf->strbuf_pflush, bus_addr);
-	}
-
-	/* Step 3: Perform flush synchronization sequence. */
-	pci_iommu_write(strbuf->strbuf_fsync, strbuf->strbuf_flushflag_pa);
-	(void) pci_iommu_read(iommu->write_complete_reg);
-	while (!PCI_STC_FLUSHFLAG_SET(strbuf))
-		membar("#LoadLoad");
+	bus_addr = sglist[0].dma_address & IO_PAGE_MASK;
+	for(i = 1; i < nelems; i++)
+		if (!sglist[i].dma_length)
+			break;
+	i--;
+	npages = (IO_PAGE_ALIGN(sglist[i].dma_address + sglist[i].dma_length)
+		  - bus_addr) >> IO_PAGE_SHIFT;
+	pci_strbuf_flush(strbuf, iommu, bus_addr, ctx, npages);
 
 	spin_unlock_irqrestore(&iommu->lock, flags);
 }
diff --git a/arch/sparc64/kernel/sbus.c b/arch/sparc64/kernel/sbus.c
index 14d9c3a..d3eca98 100644
--- a/arch/sparc64/kernel/sbus.c
+++ b/arch/sparc64/kernel/sbus.c
@@ -117,19 +117,34 @@ static void iommu_flush(struct sbus_iommu *iommu, u32 base, unsigned long npages
 
 #define STRBUF_TAG_VALID	0x02UL
 
-static void strbuf_flush(struct sbus_iommu *iommu, u32 base, unsigned long npages)
+static void sbus_strbuf_flush(struct sbus_iommu *iommu, u32 base, unsigned long npages)
 {
+	unsigned long n;
+	int limit;
+
 	iommu->strbuf_flushflag = 0UL;
-	while (npages--)
-		upa_writeq(base + (npages << IO_PAGE_SHIFT),
+	n = npages;
+	while (n--)
+		upa_writeq(base + (n << IO_PAGE_SHIFT),
 			   iommu->strbuf_regs + STRBUF_PFLUSH);
 
 	/* Whoopee cushion! */
 	upa_writeq(__pa(&iommu->strbuf_flushflag),
 		   iommu->strbuf_regs + STRBUF_FSYNC);
 	upa_readq(iommu->sbus_control_reg);
-	while (iommu->strbuf_flushflag == 0UL)
+
+	limit = 10000;
+	while (iommu->strbuf_flushflag == 0UL) {
+		limit--;
+		if (!limit)
+			break;
+		udelay(10);
 		membar("#LoadLoad");
+	}
+	if (!limit)
+		printk(KERN_WARNING "sbus_strbuf_flush: flushflag timeout "
+		       "vaddr[%08x] npages[%ld]\n",
+		       base, npages);
 }
 
 static iopte_t *alloc_streaming_cluster(struct sbus_iommu *iommu, unsigned long npages)
@@ -406,7 +421,7 @@ void sbus_unmap_single(struct sbus_dev *sdev, dma_addr_t dma_addr, size_t size,
 
 	spin_lock_irqsave(&iommu->lock, flags);
 	free_streaming_cluster(iommu, dma_base, size >> IO_PAGE_SHIFT);
-	strbuf_flush(iommu, dma_base, size >> IO_PAGE_SHIFT);
+	sbus_strbuf_flush(iommu, dma_base, size >> IO_PAGE_SHIFT);
 	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
@@ -569,7 +584,7 @@ void sbus_unmap_sg(struct sbus_dev *sdev, struct scatterlist *sg, int nents, int
 	iommu = sdev->bus->iommu;
 	spin_lock_irqsave(&iommu->lock, flags);
 	free_streaming_cluster(iommu, dvma_base, size >> IO_PAGE_SHIFT);
-	strbuf_flush(iommu, dvma_base, size >> IO_PAGE_SHIFT);
+	sbus_strbuf_flush(iommu, dvma_base, size >> IO_PAGE_SHIFT);
 	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
@@ -581,7 +596,7 @@ void sbus_dma_sync_single_for_cpu(struct sbus_dev *sdev, dma_addr_t base, size_t
 	size = (IO_PAGE_ALIGN(base + size) - (base & IO_PAGE_MASK));
 
 	spin_lock_irqsave(&iommu->lock, flags);
-	strbuf_flush(iommu, base & IO_PAGE_MASK, size >> IO_PAGE_SHIFT);
+	sbus_strbuf_flush(iommu, base & IO_PAGE_MASK, size >> IO_PAGE_SHIFT);
 	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
@@ -605,7 +620,7 @@ void sbus_dma_sync_sg_for_cpu(struct sbus_dev *sdev, struct scatterlist *sg, int
 	size = IO_PAGE_ALIGN(sg[i].dma_address + sg[i].dma_length) - base;
 
 	spin_lock_irqsave(&iommu->lock, flags);
-	strbuf_flush(iommu, base, size >> IO_PAGE_SHIFT);
+	sbus_strbuf_flush(iommu, base, size >> IO_PAGE_SHIFT);
 	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
diff --git a/drivers/sbus/char/aurora.c b/drivers/sbus/char/aurora.c
index e5fa170..650d5e9 100644
--- a/drivers/sbus/char/aurora.c
+++ b/drivers/sbus/char/aurora.c
@@ -81,10 +81,6 @@ unsigned char irqs[4] = {
 int irqhit=0;
 #endif
 
-#ifndef MIN
-#define MIN(a,b) ((a) < (b) ? (a) : (b))
-#endif
-
 static struct tty_driver *aurora_driver;
 static struct Aurora_board aurora_board[AURORA_NBOARD] = {
 	{0,},
@@ -594,7 +590,7 @@ static void aurora_transmit(struct Aurora_board const * bp, int chip)
 					    &bp->r[chip]->r[CD180_TDR]);
 				port->COR2 &= ~COR2_ETC;
 			}
-			count = MIN(port->break_length, 0xff);
+			count = min(port->break_length, 0xff);
 			sbus_writeb(CD180_C_ESC,
 				    &bp->r[chip]->r[CD180_TDR]);
 			sbus_writeb(CD180_C_DELAY,
@@ -1575,7 +1571,7 @@ static int aurora_write(struct tty_struct * tty,
 	save_flags(flags);
 	while (1) {
 		cli();
-		c = MIN(count, MIN(SERIAL_XMIT_SIZE - port->xmit_cnt - 1,
+		c = min(count, min(SERIAL_XMIT_SIZE - port->xmit_cnt - 1,
 				   SERIAL_XMIT_SIZE - port->xmit_head));
 		if (c <= 0) {
 			restore_flags(flags);
diff --git a/drivers/serial/sunsab.c b/drivers/serial/sunsab.c
index 39b788d..10e2990 100644
--- a/drivers/serial/sunsab.c
+++ b/drivers/serial/sunsab.c
@@ -61,6 +61,16 @@ struct uart_sunsab_port {
 	unsigned char			pvr_dtr_bit;	/* Which PVR bit is DTR */
 	unsigned char			pvr_dsr_bit;	/* Which PVR bit is DSR */
 	int				type;		/* SAB82532 version	*/
+
+	/* Setting configuration bits while the transmitter is active
+	 * can cause garbage characters to get emitted by the chip.
+	 * Therefore, we cache such writes here and do the real register
+	 * write the next time the transmitter becomes idle.
+	 */
+	unsigned int			cached_ebrg;
+	unsigned char			cached_mode;
+	unsigned char			cached_pvr;
+	unsigned char			cached_dafo;
 };
 
 /*
@@ -236,6 +246,7 @@ receive_chars(struct uart_sunsab_port *up,
 }
 
 static void sunsab_stop_tx(struct uart_port *, unsigned int);
+static void sunsab_tx_idle(struct uart_sunsab_port *);
 
 static void transmit_chars(struct uart_sunsab_port *up,
 			   union sab82532_irq_status *stat)
@@ -258,6 +269,7 @@ static void transmit_chars(struct uart_sunsab_port *up,
 		return;
 
 	set_bit(SAB82532_XPR, &up->irqflags);
+	sunsab_tx_idle(up);
 
 	if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
 		up->interrupt_mask1 |= SAB82532_IMR1_XPR;
@@ -397,21 +409,21 @@ static void sunsab_set_mctrl(struct uart_port *port, unsigned int mctrl)
 	struct uart_sunsab_port *up = (struct uart_sunsab_port *) port;
 
 	if (mctrl & TIOCM_RTS) {
-		writeb(readb(&up->regs->rw.mode) & ~SAB82532_MODE_FRTS,
-		       &up->regs->rw.mode);
-		writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_RTS,
-		       &up->regs->rw.mode);
+		up->cached_mode &= ~SAB82532_MODE_FRTS;
+		up->cached_mode |= SAB82532_MODE_RTS;
 	} else {
-		writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_FRTS,
-		       &up->regs->rw.mode);
-		writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_RTS,
-		       &up->regs->rw.mode);
+		up->cached_mode |= (SAB82532_MODE_FRTS |
+				    SAB82532_MODE_RTS);
 	}
 	if (mctrl & TIOCM_DTR) {
-		writeb(readb(&up->regs->rw.pvr) & ~(up->pvr_dtr_bit), &up->regs->rw.pvr);
+		up->cached_pvr &= ~(up->pvr_dtr_bit);
 	} else {
-		writeb(readb(&up->regs->rw.pvr) | up->pvr_dtr_bit, &up->regs->rw.pvr);
+		up->cached_pvr |= up->pvr_dtr_bit;
 	}
+
+	set_bit(SAB82532_REGS_PENDING, &up->irqflags);
+	if (test_bit(SAB82532_XPR, &up->irqflags))
+		sunsab_tx_idle(up);
 }
 
 /* port->lock is not held.  */
@@ -450,6 +462,25 @@ static void sunsab_stop_tx(struct uart_port *port, unsigned int tty_stop)
 }
 
 /* port->lock held by caller.  */
+static void sunsab_tx_idle(struct uart_sunsab_port *up)
+{
+	if (test_bit(SAB82532_REGS_PENDING, &up->irqflags)) {
+		u8 tmp;
+
+		clear_bit(SAB82532_REGS_PENDING, &up->irqflags);
+		writeb(up->cached_mode, &up->regs->rw.mode);
+		writeb(up->cached_pvr, &up->regs->rw.pvr);
+		writeb(up->cached_dafo, &up->regs->w.dafo);
+
+		writeb(up->cached_ebrg & 0xff, &up->regs->w.bgr);
+		tmp = readb(&up->regs->rw.ccr2);
+		tmp &= ~0xc0;
+		tmp |= (up->cached_ebrg >> 2) & 0xc0;
+		writeb(tmp, &up->regs->rw.ccr2);
+	}
+}
+
+/* port->lock held by caller.  */
 static void sunsab_start_tx(struct uart_port *port, unsigned int tty_start)
 {
 	struct uart_sunsab_port *up = (struct uart_sunsab_port *) port;
@@ -517,12 +548,16 @@ static void sunsab_break_ctl(struct uart_port *port, int break_state)
 
 	spin_lock_irqsave(&up->port.lock, flags);
 
-	val = readb(&up->regs->rw.dafo);
+	val = up->cached_dafo;
 	if (break_state)
 		val |= SAB82532_DAFO_XBRK;
 	else
 		val &= ~SAB82532_DAFO_XBRK;
-	writeb(val, &up->regs->rw.dafo);
+	up->cached_dafo = val;
+
+	set_bit(SAB82532_REGS_PENDING, &up->irqflags);
+	if (test_bit(SAB82532_XPR, &up->irqflags))
+		sunsab_tx_idle(up);
 
 	spin_unlock_irqrestore(&up->port.lock, flags);
 }
@@ -566,8 +601,9 @@ static int sunsab_startup(struct uart_port *port)
 	       SAB82532_CCR2_TOE, &up->regs->w.ccr2);
 	writeb(0, &up->regs->w.ccr3);
 	writeb(SAB82532_CCR4_MCK4 | SAB82532_CCR4_EBRG, &up->regs->w.ccr4);
-	writeb(SAB82532_MODE_RTS | SAB82532_MODE_FCTS |
-	       SAB82532_MODE_RAC, &up->regs->w.mode);
+	up->cached_mode = (SAB82532_MODE_RTS | SAB82532_MODE_FCTS |
+			   SAB82532_MODE_RAC);
+	writeb(up->cached_mode, &up->regs->w.mode);
 	writeb(SAB82532_RFC_DPS|SAB82532_RFC_RFTH_32, &up->regs->w.rfc);
 	
 	tmp = readb(&up->regs->rw.ccr0);
@@ -598,7 +634,6 @@ static void sunsab_shutdown(struct uart_port *port)
 {
 	struct uart_sunsab_port *up = (struct uart_sunsab_port *) port;
 	unsigned long flags;
-	unsigned char tmp;
 
 	spin_lock_irqsave(&up->port.lock, flags);
 
@@ -609,14 +644,13 @@ static void sunsab_shutdown(struct uart_port *port)
 	writeb(up->interrupt_mask1, &up->regs->w.imr1);
 
 	/* Disable break condition */
-	tmp = readb(&up->regs->rw.dafo);
-	tmp &= ~SAB82532_DAFO_XBRK;
-	writeb(tmp, &up->regs->rw.dafo);
+	up->cached_dafo = readb(&up->regs->rw.dafo);
+	up->cached_dafo &= ~SAB82532_DAFO_XBRK;
+	writeb(up->cached_dafo, &up->regs->rw.dafo);
 
 	/* Disable Receiver */	
-	tmp = readb(&up->regs->rw.mode);
-	tmp &= ~SAB82532_MODE_RAC;
-	writeb(tmp, &up->regs->rw.mode);
+	up->cached_mode &= ~SAB82532_MODE_RAC;
+	writeb(up->cached_mode, &up->regs->rw.mode);
 
 	/*
 	 * XXX FIXME
@@ -685,7 +719,6 @@ static void sunsab_convert_to_sab(struct uart_sunsab_port *up, unsigned int cfla
 				  unsigned int iflag, unsigned int baud,
 				  unsigned int quot)
 {
-	unsigned int ebrg;
 	unsigned char dafo;
 	int bits, n, m;
 
@@ -714,10 +747,11 @@ static void sunsab_convert_to_sab(struct uart_sunsab_port *up, unsigned int cfla
 	} else {
 		dafo |= SAB82532_DAFO_PAR_EVEN;
 	}
+	up->cached_dafo = dafo;
 
 	calc_ebrg(baud, &n, &m);
 
-	ebrg = n | (m << 6);
+	up->cached_ebrg = n | (m << 6);
 
 	up->tec_timeout = (10 * 1000000) / baud;
 	up->cec_timeout = up->tec_timeout >> 2;
@@ -770,16 +804,13 @@ static void sunsab_convert_to_sab(struct uart_sunsab_port *up, unsigned int cfla
 	uart_update_timeout(&up->port, cflag,
 			    (up->port.uartclk / (16 * quot)));
 
-	/* Now bang the new settings into the chip.  */
-	sunsab_cec_wait(up);
-	sunsab_tec_wait(up);
-	writeb(dafo, &up->regs->w.dafo);
-	writeb(ebrg & 0xff, &up->regs->w.bgr);
-	writeb((readb(&up->regs->rw.ccr2) & ~0xc0) | ((ebrg >> 2) & 0xc0),
-	       &up->regs->rw.ccr2);
-
-	writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_RAC, &up->regs->rw.mode);
-
+	/* Now schedule a register update when the chip's
+	 * transmitter is idle.
+	 */
+	up->cached_mode |= SAB82532_MODE_RAC;
+	set_bit(SAB82532_REGS_PENDING, &up->irqflags);
+	if (test_bit(SAB82532_XPR, &up->irqflags))
+		sunsab_tx_idle(up);
 }
 
 /* port->lock is not held.  */
@@ -1084,11 +1115,13 @@ static void __init sunsab_init_hw(void)
 			up->pvr_dsr_bit = (1 << 3);
 			up->pvr_dtr_bit = (1 << 2);
 		}
-		writeb((1 << 1) | (1 << 2) | (1 << 4), &up->regs->w.pvr);
-		writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_FRTS,
-		       &up->regs->rw.mode);
-		writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_RTS,
-		       &up->regs->rw.mode);
+		up->cached_pvr = (1 << 1) | (1 << 2) | (1 << 4);
+		writeb(up->cached_pvr, &up->regs->w.pvr);
+		up->cached_mode = readb(&up->regs->rw.mode);
+		up->cached_mode |= SAB82532_MODE_FRTS;
+		writeb(up->cached_mode, &up->regs->rw.mode);
+		up->cached_mode |= SAB82532_MODE_RTS;
+		writeb(up->cached_mode, &up->regs->rw.mode);
 
 		up->tec_timeout = SAB82532_MAX_TEC_TIMEOUT;
 		up->cec_timeout = SAB82532_MAX_CEC_TIMEOUT;
diff --git a/drivers/serial/sunsab.h b/drivers/serial/sunsab.h
index 686086f..b78e1f7 100644
--- a/drivers/serial/sunsab.h
+++ b/drivers/serial/sunsab.h
@@ -126,6 +126,7 @@ union sab82532_irq_status {
 /* irqflags bits */
 #define SAB82532_ALLS			0x00000001
 #define SAB82532_XPR			0x00000002
+#define SAB82532_REGS_PENDING		0x00000004
 
 /* RFIFO Status Byte */
 #define SAB82532_RSTAT_PE		0x80