linux-kernel - [PATCH 2/2] media: verisilicon: change confusingly named relaxed register access

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Message-Id: <20230616144854.3818934-2-arnd@kernel.org>
Date:   Fri, 16 Jun 2023 16:48:48 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] media: verisilicon: change confusingly named relaxed register access

From: Arnd Bergmann <arnd@...db.de>

The register abstraction has wrappers around both the normal writel()
and its writel_relaxed() counterpart, but this has led to a lot of users
ending up with the relaxed version.

There is sometimes a need to intentionally pick the relaxed accessor for
performance critical functions, but I noticed that each hantro_reg_write()
call also contains a non-relaxed readl(), which is typically much more
expensive than a writel, so there is little benefit here but an added
risk of missing a serialization against DMA.

To make this behave like other interfaces, use the normal accessor by
default and only provide the relaxed version as an alternative for
performance critical code. hantro_postproc.c is the only place that
used both the relaxed and normal writel, but this does not seem
cricital either, so change it all to the normal ones.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
I did not look whether there is an actual bug here, just noticed this
when I debugged the excessive stack usage.
---
 drivers/media/platform/verisilicon/hantro.h          |  6 +++---
 drivers/media/platform/verisilicon/hantro_postproc.c | 12 ++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/media/platform/verisilicon/hantro.h b/drivers/media/platform/verisilicon/hantro.h
index 6c5e56ce5b351..a481d957fef93 100644
--- a/drivers/media/platform/verisilicon/hantro.h
+++ b/drivers/media/platform/verisilicon/hantro.h
@@ -441,14 +441,14 @@ static __always_inline void hantro_reg_write(struct hantro_dev *vpu,
 				    const struct hantro_reg *reg,
 				    u32 val)
 {
-	vdpu_write_relaxed(vpu, vdpu_read_mask(vpu, reg, val), reg->base);
+	vdpu_write(vpu, vdpu_read_mask(vpu, reg, val), reg->base);
 }
 
-static __always_inline void hantro_reg_write_s(struct hantro_dev *vpu,
+static __always_inline void hantro_reg_write_relaxed(struct hantro_dev *vpu,
 				      const struct hantro_reg *reg,
 				      u32 val)
 {
-	vdpu_write(vpu, vdpu_read_mask(vpu, reg, val), reg->base);
+	vdpu_write_relaxed(vpu, vdpu_read_mask(vpu, reg, val), reg->base);
 }
 
 void *hantro_get_ctrl(struct hantro_ctx *ctx, u32 id);
diff --git a/drivers/media/platform/verisilicon/hantro_postproc.c b/drivers/media/platform/verisilicon/hantro_postproc.c
index c977d64105b18..0224ff68ab3fc 100644
--- a/drivers/media/platform/verisilicon/hantro_postproc.c
+++ b/drivers/media/platform/verisilicon/hantro_postproc.c
@@ -21,11 +21,11 @@
 			 val); \
 }
 
-#define HANTRO_PP_REG_WRITE_S(vpu, reg_name, val) \
+#define HANTRO_PP_REG_WRITE_RELAXED(vpu, reg_name, val) \
 { \
-	hantro_reg_write_s(vpu, \
-			   &hantro_g1_postproc_regs.reg_name, \
-			   val); \
+	hantro_reg_write_relaxed(vpu, \
+				 &hantro_g1_postproc_regs.reg_name, \
+				 val); \
 }
 
 #define VPU_PP_IN_YUYV			0x0
@@ -72,7 +72,7 @@ static void hantro_postproc_g1_enable(struct hantro_ctx *ctx)
 	dma_addr_t dst_dma;
 
 	/* Turn on pipeline mode. Must be done first. */
-	HANTRO_PP_REG_WRITE_S(vpu, pipeline_en, 0x1);
+	HANTRO_PP_REG_WRITE(vpu, pipeline_en, 0x1);
 
 	src_pp_fmt = VPU_PP_IN_NV12;
 
@@ -242,7 +242,7 @@ static void hantro_postproc_g1_disable(struct hantro_ctx *ctx)
 {
 	struct hantro_dev *vpu = ctx->dev;
 
-	HANTRO_PP_REG_WRITE_S(vpu, pipeline_en, 0x0);
+	HANTRO_PP_REG_WRITE(vpu, pipeline_en, 0x0);
 }
 
 static void hantro_postproc_g2_disable(struct hantro_ctx *ctx)
-- 
2.39.2