Dear Eric,

Some nit picks where stuff contradicts the coding style.

Am Freitag, den 13.10.2017, 17:12 -0700 schrieb Eric Anholt:

VC4's DSI1 has a bug where the AXI connection is broken for 32-bit writes from the CPU, so we use the DMA engine to DMA 32-bit values into registers instead. That sleeps, so we can't do it from the top half.

As a solution, use an interrupt thread so that all our writes happen when sleeping is is allowed.

v2: Use IRQF_ONESHOT (suggested by Boris)

Signed-off-by: Eric Anholt eric@anholt.net

Boris, that cleanup ended up working and it looks great. Thanks!

drivers/gpu/drm/vc4/vc4_dsi.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c index 554605af344e..3b74fda5662d 100644 --- a/drivers/gpu/drm/vc4/vc4_dsi.c +++ b/drivers/gpu/drm/vc4/vc4_dsi.c @@ -1360,6 +1360,25 @@ static void dsi_handle_error(struct vc4_dsi *dsi, *ret = IRQ_HANDLED; }

+/* Initial handler for port 1 where we need the reg_dma workaround.

• • The register DMA writes sleep, so we can't do it in the top half.
• • Instead we use IRQF_ONESHOT so that the IRQ gets disabled in the
• • parent interrupt contrller until our interrupt thread is done.
• */

There should be a “blank comment line” at the beginning [1].

The preferred style for long (multi-line) comments is:

/*

• This is the preferred style for multi-line
• comments in the Linux kernel source code.
• Please use it consistently.
• Description: A column of asterisks on the left side,
• with beginning and ending almost-blank lines.

*/

+static irqreturn_t vc4_dsi_irq_defer_to_thread_handler(int irq, void *data) +{

• struct vc4_dsi *dsi = data;
• u32 stat = DSI_PORT_READ(INT_STAT);
• if (!stat)

• return IRQ_NONE;
  

• return IRQ_WAKE_THREAD;

+}

+/* Normal IRQ handler for port 0, or the threaded IRQ handler for port

• • 1 where we need the reg_dma workaround.
• */

static irqreturn_t vc4_dsi_irq_handler(int irq, void *data) { struct vc4_dsi *dsi = data; @@ -1539,8 +1558,16 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data) /* Clear any existing interrupt state. */ DSI_PORT_WRITE(INT_STAT, DSI_PORT_READ(INT_STAT));

• ret = devm_request_irq(dev, platform_get_irq(pdev, 0),

• 	       vc4_dsi_irq_handler, 0, "vc4 dsi", dsi);
  

• if (dsi->reg_dma_mem) {

• ret = devm_request_threaded_irq(dev, platform_get_irq(pdev, 0),
  

• 				vc4_dsi_irq_defer_to_thread_handler,
  

• 				vc4_dsi_irq_handler,
  

• 				IRQF_ONESHOT,
  

• 				"vc4 dsi", dsi);
  

• } else {

• ret = devm_request_irq(dev, platform_get_irq(pdev, 0),
  

• 		       vc4_dsi_irq_handler, 0, "vc4 dsi", dsi);
  

• }

The braces should be removed [2].

Do not unnecessarily use braces where a single statement will do.

if (ret) { if (ret != -EPROBE_DEFER) dev_err(dev, "Failed to get interrupt: %d\n", ret);

Thanks,

Paul

[1] https://www.kernel.org/doc/html/v4.13/process/coding-style.html#commenting [2] https://www.kernel.org/doc/html/v4.13/process/coding-style.html#placing-brac...