From e8ee6c8cb61b676f1a2d6b942329e98224bd8ee9 Mon Sep 17 00:00:00 2001 From: Serge Semin Date: Fri, 31 Jul 2020 23:08:26 +0300 Subject: dmaengine: dw: Add DMA-channels mask cell support DW DMA IP-core provides a way to synthesize the DMA controller with channels having different parameters like maximum burst-length, multi-block support, maximum data width, etc. Those parameters both explicitly and implicitly affect the channels performance. Since DMA slave devices might be very demanding to the DMA performance, let's provide a functionality for the slaves to be assigned with DW DMA channels, which performance according to the platform engineer fulfill their requirements. After this patch is applied it can be done by passing the mask of suitable DMA-channels either directly in the dw_dma_slave structure instance or as a fifth cell of the DMA DT-property. If mask is zero or not provided, then there is no limitation on the channels allocation. For instance Baikal-T1 SoC is equipped with a DW DMAC engine, which first two channels are synthesized with max burst length of 16, while the rest of the channels have been created with max-burst-len=4. It would seem that the first two channels must be faster than the others and should be more preferable for the time-critical DMA slave devices. In practice it turned out that the situation is quite the opposite. The channels with max-burst-len=4 demonstrated a better performance than the channels with max-burst-len=16 even when they both had been initialized with the same settings. The performance drop of the first two DMA-channels made them unsuitable for the DW APB SSI slave device. No matter what settings they are configured with, full-duplex SPI transfers occasionally experience the Rx FIFO overflow. It means that the DMA-engine doesn't keep up with incoming data pace even though the SPI-bus is enabled with speed of 25MHz while the DW DMA controller is clocked with 50MHz signal. There is no such problem has been noticed for the channels synthesized with max-burst-len=4. Signed-off-by: Serge Semin Link: https://lore.kernel.org/r/20200731200826.9292-6-Sergey.Semin@baikalelectronics.ru Signed-off-by: Vinod Koul --- include/linux/platform_data/dma-dw.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/platform_data/dma-dw.h b/include/linux/platform_data/dma-dw.h index fbbeb2f6189b..b34a094b2258 100644 --- a/include/linux/platform_data/dma-dw.h +++ b/include/linux/platform_data/dma-dw.h @@ -26,6 +26,7 @@ struct device; * @dst_id: dst request line * @m_master: memory master for transfers on allocated channel * @p_master: peripheral master for transfers on allocated channel + * @channels: mask of the channels permitted for allocation (zero value means any) * @hs_polarity:set active low polarity of handshake interface */ struct dw_dma_slave { @@ -34,6 +35,7 @@ struct dw_dma_slave { u8 dst_id; u8 m_master; u8 p_master; + u8 channels; bool hs_polarity; }; -- cgit v1.2.3 From 145fbd1e82e6654398ace321432e3a803b8a2be4 Mon Sep 17 00:00:00 2001 From: Peter Ujfalusi Date: Fri, 28 Aug 2020 11:41:41 +0300 Subject: dmaengine: Remove unused define for dma_request_slave_channel_reason() No users left in the kernel, it can be removed. Signed-off-by: Peter Ujfalusi Link: https://lore.kernel.org/r/20200828084141.14902-1-peter.ujfalusi@ti.com Signed-off-by: Vinod Koul --- include/linux/dmaengine.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index 6fbd5c99e30c..011371b7f081 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -1527,8 +1527,6 @@ static inline int dma_get_slave_caps(struct dma_chan *chan, } #endif -#define dma_request_slave_channel_reason(dev, name) dma_request_chan(dev, name) - static inline int dmaengine_desc_set_reuse(struct dma_async_tx_descriptor *tx) { struct dma_slave_caps caps; -- cgit v1.2.3 From 7547dbd3b198f309aaff54e3528898a8a196faff Mon Sep 17 00:00:00 2001 From: Peter Ujfalusi Date: Fri, 28 Aug 2020 14:05:07 +0300 Subject: dmaengine: Mark dma_request_slave_channel() deprecated New drivers should use dma_request_chan() instead dma_request_slave_channel() dma_request_slave_channel() is a simple wrapper for dma_request_chan() eating up the error code for channel request failure and makes deferred probing impossible. Move the dma_request_slave_channel() into the header as inline function, mark it as deprecated. Signed-off-by: Peter Ujfalusi Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/20200828110507.22407-1-peter.ujfalusi@ti.com Signed-off-by: Vinod Koul --- include/linux/dmaengine.h | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'include/linux') diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index 011371b7f081..dd357a747780 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -1472,7 +1472,6 @@ void dma_issue_pending_all(void); struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param, struct device_node *np); -struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name); struct dma_chan *dma_request_chan(struct device *dev, const char *name); struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask); @@ -1502,11 +1501,6 @@ static inline struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask, { return NULL; } -static inline struct dma_chan *dma_request_slave_channel(struct device *dev, - const char *name) -{ - return NULL; -} static inline struct dma_chan *dma_request_chan(struct device *dev, const char *name) { @@ -1575,6 +1569,15 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx); #define dma_request_channel(mask, x, y) \ __dma_request_channel(&(mask), x, y, NULL) +/* Deprecated, please use dma_request_chan() directly */ +static inline struct dma_chan * __deprecated +dma_request_slave_channel(struct device *dev, const char *name) +{ + struct dma_chan *ch = dma_request_chan(dev, name); + + return IS_ERR(ch) ? NULL : ch; +} + static inline struct dma_chan *dma_request_slave_channel_compat(const dma_cap_mask_t mask, dma_filter_fn fn, void *fn_param, -- cgit v1.2.3