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From: Adrian Ratiu <adrian.ratiu@collabora.com>
To: Ezequiel Garcia <ezequiel@collabora.com>,
	Philipp Zabel <p.zabel@pengutronix.de>
Cc: Fruehberger Peter <Peter.Fruehberger@de.bosch.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org,
	Mark Brown <broonie@kernel.org>,
	kuhanh.murugasen.krishnan@intel.com,
	Daniel Vetter <daniel@ffwll.ch>,
	kernel@collabora.com, linux-media@vger.kernel.org
Subject: [PATCH 07/18] regmap: mmio: add config option to allow relaxed MMIO accesses
Date: Mon, 12 Oct 2020 23:59:46 +0300
Message-ID: <20201012205957.889185-8-adrian.ratiu@collabora.com> (raw)
In-Reply-To: <20201012205957.889185-1-adrian.ratiu@collabora.com>

On some platforms (eg armv7 due to the CONFIG_ARM_DMA_MEM_BUFFERABLE)
MMIO R/W operations always add memory barriers which can increase load,
decrease battery life or in general reduce performance unnecessarily
on devices which access a lot of configuration registers and where
ordering does not matter (eg. media accelerators like the Verisilicon /
Hantro video decoders).

Drivers used to call the relaxed MMIO variants directly but since they
are now accessing the MMIO registers via regmaps (to compensate for
for different VPU HW reg layouts via regmap fields), there is a need
for a relaxed API / config to preserve their existing behaviour.

Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
---
 drivers/base/regmap/regmap-mmio.c | 34 +++++++++++++++++++++++++++----
 include/linux/regmap.h            |  5 +++++
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/drivers/base/regmap/regmap-mmio.c b/drivers/base/regmap/regmap-mmio.c
index af967d8f975e..21193ef2a923 100644
--- a/drivers/base/regmap/regmap-mmio.c
+++ b/drivers/base/regmap/regmap-mmio.c
@@ -16,6 +16,7 @@
 struct regmap_mmio_context {
 	void __iomem *regs;
 	unsigned val_bytes;
+	bool relaxed_mmio;
 
 	bool attached_clk;
 	struct clk *clk;
@@ -72,14 +73,20 @@ static void regmap_mmio_write8(struct regmap_mmio_context *ctx,
 				unsigned int reg,
 				unsigned int val)
 {
-	writeb(val, ctx->regs + reg);
+	if (ctx->relaxed_mmio)
+		writeb_relaxed(val, ctx->regs + reg);
+	else
+		writeb(val, ctx->regs + reg);
 }
 
 static void regmap_mmio_write16le(struct regmap_mmio_context *ctx,
 				  unsigned int reg,
 				  unsigned int val)
 {
-	writew(val, ctx->regs + reg);
+	if (ctx->relaxed_mmio)
+		writew_relaxed(val, ctx->regs + reg);
+	else
+		writew(val, ctx->regs + reg);
 }
 
 static void regmap_mmio_write16be(struct regmap_mmio_context *ctx,
@@ -93,7 +100,10 @@ static void regmap_mmio_write32le(struct regmap_mmio_context *ctx,
 				  unsigned int reg,
 				  unsigned int val)
 {
-	writel(val, ctx->regs + reg);
+	if (ctx->relaxed_mmio)
+		writel_relaxed(val, ctx->regs + reg);
+	else
+		writel(val, ctx->regs + reg);
 }
 
 static void regmap_mmio_write32be(struct regmap_mmio_context *ctx,
@@ -108,7 +118,10 @@ static void regmap_mmio_write64le(struct regmap_mmio_context *ctx,
 				  unsigned int reg,
 				  unsigned int val)
 {
-	writeq(val, ctx->regs + reg);
+	if (ctx->relaxed_mmio)
+		writeq_relaxed(val, ctx->regs + reg);
+	else
+		writeq(val, ctx->regs + reg);
 }
 #endif
 
@@ -134,12 +147,18 @@ static int regmap_mmio_write(void *context, unsigned int reg, unsigned int val)
 static unsigned int regmap_mmio_read8(struct regmap_mmio_context *ctx,
 				      unsigned int reg)
 {
+	if (ctx->relaxed_mmio)
+		return readb_relaxed(ctx->regs + reg);
+
 	return readb(ctx->regs + reg);
 }
 
 static unsigned int regmap_mmio_read16le(struct regmap_mmio_context *ctx,
 				         unsigned int reg)
 {
+	if (ctx->relaxed_mmio)
+		return readw_relaxed(ctx->regs + reg);
+
 	return readw(ctx->regs + reg);
 }
 
@@ -152,6 +171,9 @@ static unsigned int regmap_mmio_read16be(struct regmap_mmio_context *ctx,
 static unsigned int regmap_mmio_read32le(struct regmap_mmio_context *ctx,
 				         unsigned int reg)
 {
+	if (ctx->relaxed_mmio)
+		return readl_relaxed(ctx->regs + reg);
+
 	return readl(ctx->regs + reg);
 }
 
@@ -165,6 +187,9 @@ static unsigned int regmap_mmio_read32be(struct regmap_mmio_context *ctx,
 static unsigned int regmap_mmio_read64le(struct regmap_mmio_context *ctx,
 				         unsigned int reg)
 {
+	if (ctx->relaxed_mmio)
+		return readq_relaxed(ctx->regs + reg);
+
 	return readq(ctx->regs + reg);
 }
 #endif
@@ -237,6 +262,7 @@ static struct regmap_mmio_context *regmap_mmio_gen_context(struct device *dev,
 
 	ctx->regs = regs;
 	ctx->val_bytes = config->val_bits / 8;
+	ctx->relaxed_mmio = config->use_relaxed_mmio;
 	ctx->clk = ERR_PTR(-ENODEV);
 
 	switch (regmap_get_val_endian(dev, &regmap_mmio, config)) {
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index e7834d98207f..126fe700d1d8 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -315,6 +315,10 @@ typedef void (*regmap_unlock)(void *);
  *                   masks are used.
  * @zero_flag_mask: If set, read_flag_mask and write_flag_mask are used even
  *                   if they are both empty.
+ * @use_relaxed_mmio: If set, MMIO R/W operations will not use memory barriers.
+ *                    This can avoid load on devices which don't require strict
+ *                    orderings, but drivers should carefully add any explicit
+ *                    memory barriers when they may require them.
  * @use_single_read: If set, converts the bulk read operation into a series of
  *                   single read operations. This is useful for a device that
  *                   does not support  bulk read.
@@ -388,6 +392,7 @@ struct regmap_config {
 
 	bool use_single_read;
 	bool use_single_write;
+	bool use_relaxed_mmio;
 	bool can_multi_write;
 
 	enum regmap_endian reg_format_endian;
-- 
2.28.0


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  parent reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-12 20:59 [PATCH 00/18] Add Hantro regmap and VC8000 h264 decode support Adrian Ratiu
2020-10-12 20:59 ` [PATCH 01/18] media: hantro: document all int reg bits up to vc8000 Adrian Ratiu
2020-10-12 20:59 ` [PATCH 02/18] media: hantro: make consistent use of decimal register notation Adrian Ratiu
2020-10-12 20:59 ` [PATCH 03/18] media: hantro: make G1_REG_SOFT_RESET Rockchip specific Adrian Ratiu
2020-10-12 20:59 ` [PATCH 04/18] media: hantro: add reset controller support Adrian Ratiu
2020-10-13  8:11   ` Philipp Zabel
2020-10-12 20:59 ` [PATCH 05/18] media: hantro: prepare clocks before variant inits are run Adrian Ratiu
2020-10-12 20:59 ` [PATCH 06/18] media: hantro: imx8mq: simplify ctrlblk reset logic Adrian Ratiu
2020-10-12 20:59 ` Adrian Ratiu [this message]
2020-10-13 10:26   ` [PATCH 07/18] regmap: mmio: add config option to allow relaxed MMIO accesses Mark Brown
2020-10-14 11:51     ` Adrian Ratiu
2020-10-14 12:12       ` Mark Brown
2020-10-14 13:00         ` Adrian Ratiu
2020-10-12 20:59 ` [PATCH 08/18] media: hantro: add initial MMIO regmap infrastructure Adrian Ratiu
2020-10-12 20:59 ` [PATCH 09/18] media: hantro: default regmap to relaxed MMIO Adrian Ratiu
2020-10-12 20:59 ` [PATCH 10/18] media: hantro: convert G1 h264 decoder to regmap fields Adrian Ratiu
2020-10-12 20:59 ` [PATCH 11/18] media: hantro: convert G1 postproc to regmap Adrian Ratiu
2020-10-12 20:59 ` [PATCH 12/18] media: hantro: add VC8000D h264 decoding Adrian Ratiu
2020-10-12 20:59 ` [PATCH 13/18] media: hantro: add VC8000D postproc support Adrian Ratiu
2020-10-12 20:59 ` [PATCH 14/18] media: hantro: make PP enablement logic a bit smarter Adrian Ratiu
2020-10-12 20:59 ` [PATCH 15/18] media: hantro: add user-selectable, platform-selectable H264 High10 Adrian Ratiu
2020-10-12 20:59 ` [PATCH 16/18] media: hantro: rename h264_dec as it's not G1 specific anymore Adrian Ratiu
2020-10-12 20:59 ` [PATCH 17/18] media: hantro: add dump registers debug option before decode start Adrian Ratiu
2020-10-12 20:59 ` [PATCH 18/18] media: hantro: document encoder reg fields Adrian Ratiu
2020-10-12 23:39 ` [PATCH 00/18] Add Hantro regmap and VC8000 h264 decode support Jonas Karlman
2020-10-13  6:48   ` Adrian Ratiu
2020-10-29 12:38   ` Ezequiel Garcia
2020-10-29 16:21     ` Jonas Karlman
2020-11-03 15:27       ` Ezequiel Garcia
2020-10-29 13:07 ` Ezequiel Garcia
2020-10-29 14:15   ` Robin Murphy
2020-10-29 14:48     ` Mark Brown
2020-10-29 16:27     ` Ezequiel Garcia
2020-10-29 17:59       ` Mark Brown

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