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| author |   Russell King <rmk+kernel@arm.linux.org.uk> | 2010-12-22 17:59:16 +0000 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2011-01-05 16:58:53 +0000 |
| commit | 38d624361b2a82d6317c379aebf81b1b28210bb0 (patch) | |
| tree | fca8b4acdba29a8550fc7e7d19de2d2228c36be8 /drivers/serial | |
| parent | ARM: PL011: Add support for transmit DMA (diff) | |
| download | linux-dev-38d624361b2a82d6317c379aebf81b1b28210bb0.tar.xz linux-dev-38d624361b2a82d6317c379aebf81b1b28210bb0.zip | |
ARM: PL011: add DMA burst threshold support for ST variants
ST Micro variants has some specific dma burst threshold compensation,
which allows them to make better use of a DMA controller. Add support
to set this up.
Based on a patch from Linus Walleij.
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'drivers/serial')
| -rw-r--r-- | drivers/serial/amba-pl011.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/serial/amba-pl011.c b/drivers/serial/amba-pl011.c index ab025dc52fa4..e76d7d000128 100644 --- a/drivers/serial/amba-pl011.c +++ b/drivers/serial/amba-pl011.c @@ -74,6 +74,7 @@ struct vendor_data { unsigned int lcrh_tx; unsigned int lcrh_rx; bool oversampling; + bool dma_threshold; }; static struct vendor_data vendor_arm = { @@ -82,6 +83,7 @@ static struct vendor_data vendor_arm = { .lcrh_tx = UART011_LCRH, .lcrh_rx = UART011_LCRH, .oversampling = false, + .dma_threshold = false, }; static struct vendor_data vendor_st = { @@ -90,6 +92,7 @@ static struct vendor_data vendor_st = { .lcrh_tx = ST_UART011_LCRH_TX, .lcrh_rx = ST_UART011_LCRH_RX, .oversampling = true, + .dma_threshold = true, }; /* Deals with DMA transactions */ @@ -527,6 +530,15 @@ static void pl011_dma_startup(struct uart_amba_port *uap) /* Turn on DMA error (RX/TX will be enabled on demand) */ uap->dmacr |= UART011_DMAONERR; writew(uap->dmacr, uap->port.membase + UART011_DMACR); + + /* + * ST Micro variants has some specific dma burst threshold + * compensation. Set this to 16 bytes, so burst will only + * be issued above/below 16 bytes. + */ + if (uap->vendor->dma_threshold) + writew(ST_UART011_DMAWM_RX_16 | ST_UART011_DMAWM_TX_16, + uap->port.membase + ST_UART011_DMAWM); } static void pl011_dma_shutdown(struct uart_amba_port *uap) |