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>

diff --git a/drivers/video/sh_mobile_lcdcfb.c b/drivers/video/sh_mobile_lcdcfb.c
index 84504d5749860a6473b3f07d08e57aad96dc1fd4..99656f593de480140c27ca3ac01a45210dc8b9f5 100644 (file)
--- 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,