[v2,1/6] ARM: tegra: export apb dma readl/writel

Commit Message

Peter De Schrijver Dec. 24, 2013, 1:32 p.m. UTC

Export APB DMA readl and writel. These are needed because we can't access
the fuses directly on Tegra20 without potentially causing a system hang.

Signed-off-by: Peter De Schrijver <[e-mail]>
---
 arch/arm/mach-tegra/apbio.c |   51 ++++++++++++++++++++++++++----------------
 include/linux/tegra-soc.h   |   16 +++++++++++++
 2 files changed, 47 insertions(+), 20 deletions(-)

Comments

Stephen Warren Jan. 6, 2014, 8:07 p.m. UTC | #1

On 12/24/2013 06:32 AM, Peter De Schrijver wrote:
> Export APB DMA readl and writel. These are needed because we can't access
> the fuses directly on Tegra20 without potentially causing a system hang.

This does a lot more than just export the functions; it also changes the
prototypes. I'm not sure why the prototype change was required/useful.
This needs to be mentioned in the commit description/subject, and the
reasoning explained too.

> diff --git a/include/linux/tegra-soc.h b/include/linux/tegra-soc.h

> +#if defined(CONFIG_TEGRA20_APB_DMA)
> +void tegra_apb_io_init(void);

This seems to be an internal function; why is this one publicly
prototyped and/or stubbed?

Peter De Schrijver Jan. 7, 2014, 12:54 p.m. UTC | #2

On Mon, Jan 06, 2014 at 09:07:26PM +0100, Stephen Warren wrote:
> On 12/24/2013 06:32 AM, Peter De Schrijver wrote:
> > Export APB DMA readl and writel. These are needed because we can't access
> > the fuses directly on Tegra20 without potentially causing a system hang.
> 
> This does a lot more than just export the functions; it also changes the
> prototypes. I'm not sure why the prototype change was required/useful.
> This needs to be mentioned in the commit description/subject, and the
> reasoning explained too.
> 
> > diff --git a/include/linux/tegra-soc.h b/include/linux/tegra-soc.h
> 
> > +#if defined(CONFIG_TEGRA20_APB_DMA)
> > +void tegra_apb_io_init(void);
> 
> This seems to be an internal function; why is this one publicly
> prototyped and/or stubbed?
> 

Ah. this might be a leftover from a previous iteration... Need to check.

Patch

diff --git a/arch/arm/mach-tegra/apbio.c b/arch/arm/mach-tegra/apbio.c
index bc47197..e0bf49d 100644
--- a/arch/arm/mach-tegra/apbio.c
+++ b/arch/arm/mach-tegra/apbio.c
@@ -32,8 +32,8 @@  static u32 *tegra_apb_bb;
 static dma_addr_t tegra_apb_bb_phys;
 static DECLARE_COMPLETION(tegra_apb_wait);
 
-static u32 tegra_apb_readl_direct(unsigned long offset);
-static void tegra_apb_writel_direct(u32 value, unsigned long offset);
+static int tegra_apb_readl_direct(unsigned long offset, u32 *value);
+static int tegra_apb_writel_direct(u32 value, unsigned long offset);
 
 static struct dma_chan *tegra_apb_dma_chan;
 static struct dma_slave_config dma_sconfig;
@@ -128,58 +128,64 @@  static int do_dma_transfer(unsigned long apb_add,
 	return 0;
 }
 
-static u32 tegra_apb_readl_using_dma(unsigned long offset)
+int tegra_apb_readl_using_dma(unsigned long offset, u32 *value)
 {
 	int ret;
 
 	if (!tegra_apb_dma_chan && !tegra_apb_dma_init())
-		return tegra_apb_readl_direct(offset);
+		return tegra_apb_readl_direct(offset, value);
 
 	mutex_lock(&tegra_apb_dma_lock);
 	ret = do_dma_transfer(offset, DMA_DEV_TO_MEM);
-	if (ret < 0) {
+	if (ret < 0)
 		pr_err("error in reading offset 0x%08lx using dma\n", offset);
-		*(u32 *)tegra_apb_bb = 0;
-	}
+	else
+		*value = *tegra_apb_bb;
+
 	mutex_unlock(&tegra_apb_dma_lock);
-	return *((u32 *)tegra_apb_bb);
+
+	return ret;
 }
 
-static void tegra_apb_writel_using_dma(u32 value, unsigned long offset)
+int tegra_apb_writel_using_dma(u32 value, unsigned long offset)
 {
 	int ret;
 
-	if (!tegra_apb_dma_chan && !tegra_apb_dma_init()) {
-		tegra_apb_writel_direct(value, offset);
-		return;
-	}
+	if (!tegra_apb_dma_chan && !tegra_apb_dma_init())
+		return tegra_apb_writel_direct(value, offset);
 
 	mutex_lock(&tegra_apb_dma_lock);
 	*((u32 *)tegra_apb_bb) = value;
 	ret = do_dma_transfer(offset, DMA_MEM_TO_DEV);
+	mutex_unlock(&tegra_apb_dma_lock);
 	if (ret < 0)
 		pr_err("error in writing offset 0x%08lx using dma\n", offset);
-	mutex_unlock(&tegra_apb_dma_lock);
+
+	return ret;
 }
 #else
 #define tegra_apb_readl_using_dma tegra_apb_readl_direct
 #define tegra_apb_writel_using_dma tegra_apb_writel_direct
 #endif
 
-typedef u32 (*apbio_read_fptr)(unsigned long offset);
-typedef void (*apbio_write_fptr)(u32 value, unsigned long offset);
+typedef int (*apbio_read_fptr)(unsigned long offset, u32 *value);
+typedef int (*apbio_write_fptr)(u32 value, unsigned long offset);
 
 static apbio_read_fptr apbio_read;
 static apbio_write_fptr apbio_write;
 
-static u32 tegra_apb_readl_direct(unsigned long offset)
+static int tegra_apb_readl_direct(unsigned long offset, u32 *value)
 {
-	return readl(IO_ADDRESS(offset));
+	*value = readl(IO_ADDRESS(offset));
+
+	return 0;
 }
 
-static void tegra_apb_writel_direct(u32 value, unsigned long offset)
+static int tegra_apb_writel_direct(u32 value, unsigned long offset)
 {
 	writel(value, IO_ADDRESS(offset));
+
+	return 0;
 }
 
 void tegra_apb_io_init(void)
@@ -197,7 +203,12 @@  void tegra_apb_io_init(void)
 
 u32 tegra_apb_readl(unsigned long offset)
 {
-	return apbio_read(offset);
+	u32 val;
+
+	if (apbio_read(offset, &val) < 0)
+		return 0;
+	else
+		return val;
 }
 
 void tegra_apb_writel(u32 value, unsigned long offset)
diff --git a/include/linux/tegra-soc.h b/include/linux/tegra-soc.h
index 95f611d..f53fe9c 100644
--- a/include/linux/tegra-soc.h
+++ b/include/linux/tegra-soc.h
@@ -19,4 +19,20 @@ 
 
 u32 tegra_read_chipid(void);
 
+
+#if defined(CONFIG_TEGRA20_APB_DMA)
+void tegra_apb_io_init(void);
+int tegra_apb_readl_using_dma(unsigned long offset, u32 *value);
+int tegra_apb_writel_using_dma(u32 value, unsigned long offset);
+#else
+static inline void tegra_apb_io_init(void) {}
+static inline int tegra_apb_readl_using_dma(unsigned long offset, u32 *value)
+{
+	return -EINVAL;
+}
+static inline int tegra_apb_writel_using_dma(u32 value, unsigned long offset)
+{
+	return -EINVAL;
+}
+#endif
 #endif /* __LINUX_TEGRA_SOC_H_ */