[PATCH v6 1/3] dmaengine: imx-sdma: add clock ratio 1:1 check

From: Angus Ainslie (Purism)
Date: Mon Jan 28 2019 - 12:20:12 EST


On i.mx8 mscale B0 chip, AHB/SDMA clock ratio 2:1 can't be supportted,
since SDMA clock ratio has to be increased to 250Mhz, AHB can't reach
to 500Mhz, so use 1:1 instead.

Based on NXP commit MLK-16841-1 by Robin Gong <yibin.gong@xxxxxxx>

Signed-off-by: Angus Ainslie (Purism) <angus@xxxxxxxx>
Reviewed-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
---
drivers/dma/imx-sdma.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index 0b3a67ff8e82..757fad2fbfae 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -440,6 +440,8 @@ struct sdma_engine {
unsigned int irq;
dma_addr_t bd0_phys;
struct sdma_buffer_descriptor *bd0;
+ /* clock ratio for AHB:SDMA core. 1:1 is 1, 2:1 is 0*/
+ bool clk_ratio;
};

static int sdma_config_write(struct dma_chan *chan,
@@ -662,8 +664,11 @@ static int sdma_run_channel0(struct sdma_engine *sdma)
dev_err(sdma->dev, "Timeout waiting for CH0 ready\n");

/* Set bits of CONFIG register with dynamic context switching */
- if (readl(sdma->regs + SDMA_H_CONFIG) == 0)
- writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG);
+ reg = readl(sdma->regs + SDMA_H_CONFIG);
+ if ((reg & SDMA_H_CONFIG_CSM) == 0) {
+ reg |= SDMA_H_CONFIG_CSM;
+ writel_relaxed(reg, sdma->regs + SDMA_H_CONFIG);
+ }

return ret;
}
@@ -1840,6 +1845,9 @@ static int sdma_init(struct sdma_engine *sdma)
if (ret)
goto disable_clk_ipg;

+ if (clk_get_rate(sdma->clk_ahb) == clk_get_rate(sdma->clk_ipg))
+ sdma->clk_ratio = 1;
+
/* Be sure SDMA has not started yet */
writel_relaxed(0, sdma->regs + SDMA_H_C0PTR);

@@ -1880,8 +1888,10 @@ static int sdma_init(struct sdma_engine *sdma)
writel_relaxed(0x4050, sdma->regs + SDMA_CHN0ADDR);

/* Set bits of CONFIG register but with static context switching */
- /* FIXME: Check whether to set ACR bit depending on clock ratios */
- writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
+ if (sdma->clk_ratio)
+ writel_relaxed(SDMA_H_CONFIG_ACR, sdma->regs + SDMA_H_CONFIG);
+ else
+ writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);

writel_relaxed(ccb_phys, sdma->regs + SDMA_H_C0PTR);

--
2.17.1