From 451fd82dc148bd5ac9ed5b19b6915a1afe32b9cb Mon Sep 17 00:00:00 2001 From: Peter Ujfalusi Date: Thu, 3 Jun 2010 07:39:33 +0300 Subject: OMAP3: McBSP: Change the way how the FIFO is handled Use the actual FIFO size in words as buffer_size on OMAP3. Change the threshold configuration to use 1 based numbering, when specifying the allowed threshold maximum or the McBSP threshold value. Set the default maximum threshold to (buffer_size - 0x10) intialy. >From users of McBSP, now it is expected to use this method. Asking for threshold 1 means that the value written to threshold registers are going to be 0, which means 1 word threshold. Signed-off-by: Peter Ujfalusi Acked-by: Jarkko Nikula Acked-by: Mark Brown Acked-by: Tony Lindgren Signed-off-by: Liam Girdwood --- arch/arm/plat-omap/mcbsp.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) (limited to 'arch/arm/plat-omap/mcbsp.c') diff --git a/arch/arm/plat-omap/mcbsp.c b/arch/arm/plat-omap/mcbsp.c index 8bab0b2..4ef4604 100644 --- a/arch/arm/plat-omap/mcbsp.c +++ b/arch/arm/plat-omap/mcbsp.c @@ -481,9 +481,9 @@ int omap_st_is_enabled(unsigned int id) EXPORT_SYMBOL(omap_st_is_enabled); /* - * omap_mcbsp_set_tx_threshold configures how to deal - * with transmit threshold. the threshold value and handler can be - * configure in here. + * omap_mcbsp_set_rx_threshold configures the transmit threshold in words. + * The threshold parameter is 1 based, and it is converted (threshold - 1) + * for the THRSH2 register. */ void omap_mcbsp_set_tx_threshold(unsigned int id, u16 threshold) { @@ -498,14 +498,15 @@ void omap_mcbsp_set_tx_threshold(unsigned int id, u16 threshold) } mcbsp = id_to_mcbsp_ptr(id); - MCBSP_WRITE(mcbsp, THRSH2, threshold); + if (threshold && threshold <= mcbsp->max_tx_thres) + MCBSP_WRITE(mcbsp, THRSH2, threshold - 1); } EXPORT_SYMBOL(omap_mcbsp_set_tx_threshold); /* - * omap_mcbsp_set_rx_threshold configures how to deal - * with receive threshold. the threshold value and handler can be - * configure in here. + * omap_mcbsp_set_rx_threshold configures the receive threshold in words. + * The threshold parameter is 1 based, and it is converted (threshold - 1) + * for the THRSH1 register. */ void omap_mcbsp_set_rx_threshold(unsigned int id, u16 threshold) { @@ -520,7 +521,8 @@ void omap_mcbsp_set_rx_threshold(unsigned int id, u16 threshold) } mcbsp = id_to_mcbsp_ptr(id); - MCBSP_WRITE(mcbsp, THRSH1, threshold); + if (threshold && threshold <= mcbsp->max_rx_thres) + MCBSP_WRITE(mcbsp, THRSH1, threshold - 1); } EXPORT_SYMBOL(omap_mcbsp_set_rx_threshold); @@ -1697,8 +1699,16 @@ static inline void __devinit omap34xx_device_init(struct omap_mcbsp *mcbsp) { mcbsp->dma_op_mode = MCBSP_DMA_MODE_ELEMENT; if (cpu_is_omap34xx()) { - mcbsp->max_tx_thres = max_thres(mcbsp); - mcbsp->max_rx_thres = max_thres(mcbsp); + /* + * Initially configure the maximum thresholds to a safe value. + * The McBSP FIFO usage with these values should not go under + * 16 locations. + * If the whole FIFO without safety buffer is used, than there + * is a possibility that the DMA will be not able to push the + * new data on time, causing channel shifts in runtime. + */ + mcbsp->max_tx_thres = max_thres(mcbsp) - 0x10; + mcbsp->max_rx_thres = max_thres(mcbsp) - 0x10; /* * REVISIT: Set dmap_op_mode to THRESHOLD as default * for mcbsp2 instances. -- cgit v1.1