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 */
--
2.49.0On 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
> >
> >
© 2016 - 2025 Red Hat, Inc.