dmaengine: uniphier-xdmac: Add UniPhier external DMA controller driver

Hello Kunihiko Hayashi,

The patch 667b9251440b: "dmaengine: uniphier-xdmac: Add UniPhier external DMA controller driver" from Feb 21, 2020, leads to the following static checker warning:

drivers/dma/uniphier-xdmac.c:212 uniphier_xdmac_chan_stop()
warn: sleeping in atomic context

drivers/dma/uniphier-xdmac.c

    197 static int uniphier_xdmac_chan_stop(struct uniphier_xdmac_chan *xc)
    198 {
    199 	u32 val;
    200 
    201 	/* disable interrupt */
    202 	val = readl(xc->reg_ch_base + XDMAC_IEN);
    203 	val &= ~(XDMAC_IEN_ENDIEN | XDMAC_IEN_ERRIEN);
    204 	writel(val, xc->reg_ch_base + XDMAC_IEN);
    205 
    206 	/* stop XDMAC */
    207 	val = readl(xc->reg_ch_base + XDMAC_TSS);
    208 	val &= ~XDMAC_TSS_REQ;
    209 	writel(0, xc->reg_ch_base + XDMAC_TSS);
    210 
    211 	/* wait until transfer is stopped */
--> 212 	return readl_poll_timeout(xc->reg_ch_base + XDMAC_STAT, val,
    213 				  !(val & XDMAC_STAT_TENF), 100, 1000);
                                                                    ^^^

This 100 means it can sleep. The function is always called with a spin_lock held.

    214 }

regards,
dan carpenter