Commit 50d7d5bf authored Nov 12, 2008 by Jean-Christophe Lallemand Committed by Linus Torvalds Nov 12, 2008

atmel_spi: work-around required for new HW bug in AT91SAM9263 Rev.B SPI controller



We're working with an AT91SAM9263 Rev B in our design and I experienced
some inconsistency in spi-based touchscreen usage between our board and
the Atmel evaluation kit we have that runs on a Rev A chip.

The data was apparently delayed by 1 byte and got ridiculous data out of
the touchscreen driver, very strange.  As everything looked normal in
the spi, touchscreen and dma logs, I contacted the Atmel support and
they triggered me on a new HW bug that appeared in the Rev B SPI
controller.

The problem is that the SPI controller on the Rev B needs that the
software reset is performed two times so that it's performed correctly.

Applying the patch below solves the issue on my Rev B board.  I've tested
it as well on my Rev A evaluation kit and it has apparently no unwanted
side effect, things continue to work as expected.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 79b92f2b

drivers/spi/atmel_spi.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -766,6 +766,7 @@ static int __init atmel_spi_probe(struct platform_device *pdev)
		/* Initialize the hardware */
		clk_enable(clk);
		spi_writel(as, CR, SPI_BIT(SWRST));
		spi_writel(as, CR, SPI_BIT(SWRST)); /* AT91SAM9263 Rev B workaround */
		spi_writel(as, MR, SPI_BIT(MSTR) \| SPI_BIT(MODFDIS));
		spi_writel(as, PTCR, SPI_BIT(RXTDIS) \| SPI_BIT(TXTDIS));
		spi_writel(as, CR, SPI_BIT(SPIEN));
		@@ -782,6 +783,7 @@ static int __init atmel_spi_probe(struct platform_device *pdev)

		out_reset_hw:
		spi_writel(as, CR, SPI_BIT(SWRST));
		spi_writel(as, CR, SPI_BIT(SWRST)); /* AT91SAM9263 Rev B workaround */
		clk_disable(clk);
		free_irq(irq, master);
		out_unmap_regs:
		@@ -805,6 +807,7 @@ static int __exit atmel_spi_remove(struct platform_device *pdev)
		spin_lock_irq(&as->lock);
		as->stopping = 1;
		spi_writel(as, CR, SPI_BIT(SWRST));
		spi_writel(as, CR, SPI_BIT(SWRST)); /* AT91SAM9263 Rev B workaround */
		spi_readl(as, SR);
		spin_unlock_irq(&as->lock);

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