mmc_spi: Fix mmc-over-spi regression (460cd058) · Commits · 戴 / test

drivers/mmc/host/mmc_spi.c

+33 −19

Original line number	Diff line number	Diff line
		@@ -1165,6 +1165,23 @@ mmc_spi_detect_irq(int irq, void *mmc)
		return IRQ_HANDLED;
		}

		struct count_children {
		unsigned n;
		struct bus_type *bus;
		};

		static int maybe_count_child(struct device dev, void c)
		{
		struct count_children *ccp = c;

		if (dev->bus == ccp->bus) {
		if (ccp->n)
		return -EBUSY;
		ccp->n++;
		}
		return 0;
		}

		static int mmc_spi_probe(struct spi_device *spi)
		{
		void *ones;
		@@ -1188,33 +1205,30 @@ static int mmc_spi_probe(struct spi_device *spi)
		return status;
		}

		/* We can use the bus safely iff nobody else will interfere with
		* us. That is, either we have the experimental exclusive access
		* primitives ... or else there's nobody to share it with.
		/* We can use the bus safely iff nobody else will interfere with us.
		* Most commands consist of one SPI message to issue a command, then
		* several more to collect its response, then possibly more for data
		* transfer. Clocking access to other devices during that period will
		* corrupt the command execution.
		*
		* Until we have software primitives which guarantee non-interference,
		* we'll aim for a hardware-level guarantee.
		*
		* REVISIT we can't guarantee another device won't be added later...
		*/
		if (spi->master->num_chipselect > 1) {
		struct device *parent = spi->dev.parent;
		struct count_children cc;

		/* If there are multiple devices on this bus, we
		* can't proceed.
		*/
		spin_lock(&parent->klist_children.k_lock);
		if (parent->klist_children.k_list.next
		!= parent->klist_children.k_list.prev)
		status = -EMLINK;
		else
		status = 0;
		spin_unlock(&parent->klist_children.k_lock);
		cc.n = 0;
		cc.bus = spi->dev.bus;
		status = device_for_each_child(spi->dev.parent, &cc,
		maybe_count_child);
		if (status < 0) {
		dev_err(&spi->dev, "can't share SPI bus\n");
		return status;
		}

		/* REVISIT we can't guarantee another device won't
		* be added later. It's uncommon though ... for now,
		* work as if this is safe.
		*/
		dev_warn(&spi->dev, "ASSUMING unshared SPI bus!\n");
		dev_warn(&spi->dev, "ASSUMING SPI bus stays unshared!\n");
		}

		/* We need a supply of ones to transmit. This is the only time

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