The i3c abstraction excepts u8 buffers, but some controllers have a bus
width of 32-bits and don't support flagging valid bytes, so it is
required to read/write long words and to use memcpy on the remainder of
the number of bytes by 32-bits to not write/read outside the buffer
bounds.

Signed-off-by: Jorge Marques <jorge.marques@analog.com>
---
 drivers/i3c/internals.h | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
index 433f6088b7cec8c77288ee24dbee8b18338aa1eb..88887b12122efafac81bcfdd093d943259e13a08 100644
--- a/drivers/i3c/internals.h
+++ b/drivers/i3c/internals.h
@@ -22,4 +22,41 @@ int i3c_dev_enable_ibi_locked(struct i3c_dev_desc *dev);
 int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev,
 			       const struct i3c_ibi_setup *req);
 void i3c_dev_free_ibi_locked(struct i3c_dev_desc *dev);
+
+/**
+ * i3c_master_writesl- Write bytes to long memory region from byte array
+ * @addr: Register to write to
+ * @bytes: Pointer to the data bytes to write
+ * @nbytes: Number of bytes to write
+ */
+static inline void i3c_writel_fifo(void __iomem *addr, const void *bytes,
+				   int nbytes)
+{
+	writesl(addr, bytes, nbytes / 4);
+	if (nbytes & 3) {
+		u32 tmp = 0;
+
+		memcpy(&tmp, bytes + (nbytes & ~3), nbytes & 3);
+		writel(tmp, addr);
+	}
+}
+
+/**
+ * i3c_master_readsl - Read bytes from long memory region to byte array
+ * @addr: Register to read from
+ * @bytes: Pointer to the buffer to store read bytes
+ * @nbytes: Number of bytes to read
+ */
+static inline void i3c_readl_fifo(const void __iomem *addr, void *bytes,
+				  int nbytes)
+{
+	readsl(addr, bytes, nbytes / 4);
+	if (nbytes & 3) {
+		u32 tmp;
+
+		tmp = readl(addr);
+		memcpy(bytes + (nbytes & ~3), &tmp, nbytes & 3);
+	}
+}
+
 #endif /* I3C_INTERNAL_H */

-- 
2.49.0

On Sun, Jun 22, 2025 at 11:18:58AM +0200, Jorge Marques wrote:
> The i3c abstraction excepts u8 buffers, but some controllers have a bus
> width of 32-bits and don't support flagging valid bytes, so it is
> required to read/write long words and to use memcpy on the remainder of
> the number of bytes by 32-bits to not write/read outside the buffer
> bounds.
> 
> Signed-off-by: Jorge Marques <jorge.marques@analog.com>

Despite Frank's valid comments, I tested this code with the Renesas
driver and it worked so far. Thanks!

Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

On Sun, Jun 22, 2025 at 11:18:58AM +0200, Jorge Marques wrote:
> The i3c abstraction excepts u8 buffers, but some controllers have a bus
                      ^ expects?

> width of 32-bits and don't support flagging valid bytes, so it is
> required to read/write long words and to use memcpy on the remainder of
> the number of bytes by 32-bits to not write/read outside the buffer
> bounds.

The I3C abstraction expects u8 buffers, but some controllers operate with
a 32-bit bus width FIFO and cannot flag valid bytes individually. To avoid
reading or writing outside the buffer bounds, use 32-bit accesses where
possible and apply memcpy for any remaining bytes.

Frank
>
> Signed-off-by: Jorge Marques <jorge.marques@analog.com>
> ---
>  drivers/i3c/internals.h | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
> index 433f6088b7cec8c77288ee24dbee8b18338aa1eb..88887b12122efafac81bcfdd093d943259e13a08 100644
> --- a/drivers/i3c/internals.h
> +++ b/drivers/i3c/internals.h
> @@ -22,4 +22,41 @@ int i3c_dev_enable_ibi_locked(struct i3c_dev_desc *dev);
>  int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev,
>  			       const struct i3c_ibi_setup *req);
>  void i3c_dev_free_ibi_locked(struct i3c_dev_desc *dev);
> +
> +/**
> + * i3c_master_writesl- Write bytes to long memory region from byte array

i3c_writel_fifo - Write data buffer to 32bit FIFO

> + * @addr: Register to write to

FIFO address

> + * @bytes: Pointer to the data bytes to write

bytes and nbytes is too similar, can you rename bytes to buf?

Check read_fifo also.

Frank
> + * @nbytes: Number of bytes to write
> + */
> +static inline void i3c_writel_fifo(void __iomem *addr, const void *bytes,
> +				   int nbytes)
> +{
> +	writesl(addr, bytes, nbytes / 4);
> +	if (nbytes & 3) {
> +		u32 tmp = 0;
> +
> +		memcpy(&tmp, bytes + (nbytes & ~3), nbytes & 3);
> +		writel(tmp, addr);
> +	}
> +}
> +
> +/**
> + * i3c_master_readsl - Read bytes from long memory region to byte array
> + * @addr: Register to read from
> + * @bytes: Pointer to the buffer to store read bytes
> + * @nbytes: Number of bytes to read
> + */
> +static inline void i3c_readl_fifo(const void __iomem *addr, void *bytes,
> +				  int nbytes)
> +{
> +	readsl(addr, bytes, nbytes / 4);
> +	if (nbytes & 3) {
> +		u32 tmp;
> +
> +		tmp = readl(addr);
> +		memcpy(bytes + (nbytes & ~3), &tmp, nbytes & 3);
> +	}
> +}
> +
>  #endif /* I3C_INTERNAL_H */
>
> --
> 2.49.0
>
>

On Mon, Jun 23, 2025 at 11:43:19AM -0400, Frank Li wrote:
> On Sun, Jun 22, 2025 at 11:18:58AM +0200, Jorge Marques wrote:
> > The i3c abstraction excepts u8 buffers, but some controllers have a bus
>                       ^ expects?
> 
> > width of 32-bits and don't support flagging valid bytes, so it is
> > required to read/write long words and to use memcpy on the remainder of
> > the number of bytes by 32-bits to not write/read outside the buffer
> > bounds.
> 
> The I3C abstraction expects u8 buffers, but some controllers operate with
> a 32-bit bus width FIFO and cannot flag valid bytes individually. To avoid
> reading or writing outside the buffer bounds, use 32-bit accesses where
> possible and apply memcpy for any remaining bytes.
Hi Frank,

gotcha,
> 
> Frank
> >
> > Signed-off-by: Jorge Marques <jorge.marques@analog.com>
> > ---
> >  drivers/i3c/internals.h | 37 +++++++++++++++++++++++++++++++++++++
> >  1 file changed, 37 insertions(+)
> >
> > diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
> > index 433f6088b7cec8c77288ee24dbee8b18338aa1eb..88887b12122efafac81bcfdd093d943259e13a08 100644
> > --- a/drivers/i3c/internals.h
> > +++ b/drivers/i3c/internals.h
> > @@ -22,4 +22,41 @@ int i3c_dev_enable_ibi_locked(struct i3c_dev_desc *dev);
> >  int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev,
> >  			       const struct i3c_ibi_setup *req);
> >  void i3c_dev_free_ibi_locked(struct i3c_dev_desc *dev);
> > +
> > +/**
> > + * i3c_master_writesl- Write bytes to long memory region from byte array
> 
> i3c_writel_fifo - Write data buffer to 32bit FIFO
> 
> > + * @addr: Register to write to
> 
> FIFO address
> 
> > + * @bytes: Pointer to the data bytes to write
> 
> bytes and nbytes is too similar, can you rename bytes to buf?
Yep
> 
> Check read_fifo also.
Ack
> 
> Frank

Regards,
Jorge
> > + * @nbytes: Number of bytes to write
> > + */
> > +static inline void i3c_writel_fifo(void __iomem *addr, const void *bytes,
> > +				   int nbytes)
> > +{
> > +	writesl(addr, bytes, nbytes / 4);
> > +	if (nbytes & 3) {
> > +		u32 tmp = 0;
> > +
> > +		memcpy(&tmp, bytes + (nbytes & ~3), nbytes & 3);
> > +		writel(tmp, addr);
> > +	}
> > +}
> > +
> > +/**
> > + * i3c_master_readsl - Read bytes from long memory region to byte array
> > + * @addr: Register to read from
> > + * @bytes: Pointer to the buffer to store read bytes
> > + * @nbytes: Number of bytes to read
> > + */
> > +static inline void i3c_readl_fifo(const void __iomem *addr, void *bytes,
> > +				  int nbytes)
> > +{
> > +	readsl(addr, bytes, nbytes / 4);
> > +	if (nbytes & 3) {
> > +		u32 tmp;
> > +
> > +		tmp = readl(addr);
> > +		memcpy(bytes + (nbytes & ~3), &tmp, nbytes & 3);
> > +	}
> > +}
> > +
> >  #endif /* I3C_INTERNAL_H */
> >
> > --
> > 2.49.0
> >
> >