fbdev: sh_mobile_lcdc: Don't acknowlege interrupts unintentionally

The LDINTR register caries both interrupt enable and interrupt status
bits. When setting or clearing interrupt enable bits, write all status
bits to 1 to avoid acknowledging interrupts by mistake.

When acknowledging interrupts, write 1 to all non-triggered interrupt
bits to avoid losing interrupts.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 8 insertions, 12 deletions

diff --git a/drivers/video/sh_mobile_lcdcfb.c b/drivers/video/sh_mobile_lcdcfb.c
index 84504d574986..99656f593de4 100644
--- a/drivers/video/sh_mobile_lcdcfb.c
+++ b/drivers/video/sh_mobile_lcdcfb.c
@@ -318,19 +318,13 @@ static irqreturn_t sh_mobile_lcdc_irq(int irq, void *data)
 {
         struct sh_mobile_lcdc_priv *priv = data;
         struct sh_mobile_lcdc_chan *ch;
-        unsigned long tmp;
         unsigned long ldintr;
         int is_sub;
         int k;
 
-        /* acknowledge interrupt */
-        ldintr = tmp = lcdc_read(priv, _LDINTR);
-        /*
-         * disable further VSYNC End IRQs, preserve all other enabled IRQs,
-         * write 0 to bits 0-6 to ack all triggered IRQs.
-         */
-        tmp &= ~LDINTR_STATUS_MASK & ~LDINTR_VEE;
-        lcdc_write(priv, _LDINTR, tmp);
+        /* Acknowledge interrupts and disable further VSYNC End IRQs. */
+        ldintr = lcdc_read(priv, _LDINTR);
+        lcdc_write(priv, _LDINTR, (ldintr ^ LDINTR_STATUS_MASK) & ~LDINTR_VEE);
 
         /* figure out if this interrupt is for main or sub lcd */
         is_sub = (lcdc_read(priv, _LDSR) & LDSR_MSS) ? 1 : 0;
@@ -342,7 +336,7 @@ static irqreturn_t sh_mobile_lcdc_irq(int irq, void *data)
                 if (!ch->enabled)
                         continue;
 
-                /* Frame Start */
+                /* Frame End */
                 if (ldintr & LDINTR_FS) {
                         if (is_sub == lcdc_chan_is_sublcd(ch)) {
                                 ch->frame_end = 1;
@@ -971,9 +965,11 @@ static int sh_mobile_wait_for_vsync(struct fb_info *info)
         unsigned long ldintr;
         int ret;
 
-        /* Enable VSync End interrupt */
+        /* Enable VSync End interrupt and be careful not to acknowledge any
+         * pending interrupt.
+         */
         ldintr = lcdc_read(ch->lcdc, _LDINTR);
-        ldintr |= LDINTR_VEE;
+        ldintr |= LDINTR_VEE | LDINTR_STATUS_MASK;
         lcdc_write(ch->lcdc, _LDINTR, ldintr);
 
         ret = wait_for_completion_interruptible_timeout(&ch->vsync_completion,