gpu: host1x: Syncpoint interrupt performance optimization

Optimize performance of syncpoint interrupt handling by reading
the status register in 64-bit chunks when possible, and skipping
processing when the read value is zero.

Signed-off-by: Mikko Perttunen <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

drivers/gpu/host1x/dev.c

···
 	return readl(sync_regs + r);
 }
 
+#ifdef CONFIG_64BIT
+u64 host1x_sync_readq(struct host1x *host1x, u32 r)
+{
+	void __iomem *sync_regs = host1x->regs + host1x->info->sync_offset;
+
+	return readq(sync_regs + r);
+}
+#endif
+
 void host1x_ch_writel(struct host1x_channel *ch, u32 v, u32 r)
 {
 	writel(v, ch->regs + r);

drivers/gpu/host1x/dev.h

···
 u32 host1x_hypervisor_readl(struct host1x *host1x, u32 r);
 void host1x_sync_writel(struct host1x *host1x, u32 v, u32 r);
 u32 host1x_sync_readl(struct host1x *host1x, u32 r);
+#ifdef CONFIG_64BIT
+u64 host1x_sync_readq(struct host1x *host1x, u32 r);
+#endif
 void host1x_ch_writel(struct host1x_channel *ch, u32 v, u32 r);
 u32 host1x_ch_readl(struct host1x_channel *ch, u32 r);
 

drivers/gpu/host1x/hw/intr_hw.c

···
 #include "../intr.h"
 #include "../dev.h"
 
+static void process_32_syncpts(struct host1x *host, unsigned long val, u32 reg_offset)
+{
+	unsigned int id;
+
+	if (!val)
+		return;
+
+	host1x_sync_writel(host, val, HOST1X_SYNC_SYNCPT_THRESH_INT_DISABLE(reg_offset));
+	host1x_sync_writel(host, val, HOST1X_SYNC_SYNCPT_THRESH_CPU0_INT_STATUS(reg_offset));
+
+	for_each_set_bit(id, &val, 32)
+		host1x_intr_handle_interrupt(host, reg_offset * 32 + id);
+}
+
 static irqreturn_t syncpt_thresh_isr(int irq, void *dev_id)
 {
 	struct host1x_intr_irq_data *irq_data = dev_id;
 	struct host1x *host = irq_data->host;
 	unsigned long reg;
-	unsigned int i, id;
+	unsigned int i;
 
+#if !defined(CONFIG_64BIT)
 	for (i = irq_data->offset; i < DIV_ROUND_UP(host->info->nb_pts, 32);
 	     i += host->num_syncpt_irqs) {
 		reg = host1x_sync_readl(host,
 			HOST1X_SYNC_SYNCPT_THRESH_CPU0_INT_STATUS(i));
 
-		host1x_sync_writel(host, reg,
-			HOST1X_SYNC_SYNCPT_THRESH_INT_DISABLE(i));
-		host1x_sync_writel(host, reg,
+		process_32_syncpts(host, reg, i);
+	}
+#elif HOST1X_HW == 6 || HOST1X_HW == 7
+	/*
+	 * Tegra186 and Tegra194 have the first INT_STATUS register not 64-bit aligned,
+	 * and only have one interrupt line.
+	 */
+	reg = host1x_sync_readl(host, HOST1X_SYNC_SYNCPT_THRESH_CPU0_INT_STATUS(0));
+	process_32_syncpts(host, reg, 0);
+
+	for (i = 1; i < (host->info->nb_pts / 32) - 1; i += 2) {
+		reg = host1x_sync_readq(host,
 			HOST1X_SYNC_SYNCPT_THRESH_CPU0_INT_STATUS(i));
 
-		for_each_set_bit(id, &reg, 32)
-			host1x_intr_handle_interrupt(host, i * 32 + id);
+		process_32_syncpts(host, lower_32_bits(reg), i);
+		process_32_syncpts(host, upper_32_bits(reg), i + 1);
 	}
+
+	reg = host1x_sync_readl(host, HOST1X_SYNC_SYNCPT_THRESH_CPU0_INT_STATUS(i));
+	process_32_syncpts(host, reg, i);
+#else
+	/* All 64-bit capable SoCs have number of syncpoints divisible by 64 */
+	for (i = irq_data->offset; i < DIV_ROUND_UP(host->info->nb_pts, 64);
+	     i += host->num_syncpt_irqs) {
+		reg = host1x_sync_readq(host,
+			HOST1X_SYNC_SYNCPT_THRESH_CPU0_INT_STATUS(i * 2));
+
+		process_32_syncpts(host, lower_32_bits(reg), i * 2 + 0);
+		process_32_syncpts(host, upper_32_bits(reg), i * 2 + 1);
+	}
+#endif
 
 	return IRQ_HANDLED;
 }
···
 
 	/*
 	 * Program threshold interrupt destination among 8 lines per VM,
-	 * per syncpoint. For each group of 32 syncpoints (corresponding to one
-	 * interrupt status register), direct to one interrupt line, going
+	 * per syncpoint. For each group of 64 syncpoints (corresponding to two
+	 * interrupt status registers), direct to one interrupt line, going
 	 * around in a round robin fashion.
 	 */
 	for (id = 0; id < host->info->nb_pts; id++) {
-		u32 reg_offset = id / 32;
+		u32 reg_offset = id / 64;
 		u32 irq_index = reg_offset % host->num_syncpt_irqs;
 
 		host1x_sync_writel(host, irq_index, HOST1X_SYNC_SYNCPT_INTR_DEST(id));