linux-kernel - Re: [PATCH v3 1/3] i3c: master: Add inline i3c_readl_fifo() and i3c_writel

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Message-ID: <aFrpra9j69OkkMbL@lizhi-Precision-Tower-5810>
Date: Tue, 24 Jun 2025 14:08:45 -0400
From: Frank Li <Frank.li@....com>
To: Jorge Marques <jorge.marques@...log.com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Przemysław Gaj <pgaj@...ence.com>,
	linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] i3c: master: Add inline i3c_readl_fifo() and
 i3c_writel_fifo()

On Tue, Jun 24, 2025 at 11:06:04AM +0200, Jorge Marques wrote:
> 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
>
> Signed-off-by: Jorge Marques <jorge.marques@...log.com>

Reviewed-by: Frank Li <Frank.Li@....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..6a11437fee47bd1d19354e983d4a561a4356b08d 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_writel_fifo - Write data buffer to 32bit FIFO
> + * @addr: FIFO Address to write to
> + * @buf: Pointer to the data bytes to write
> + * @nbytes: Number of bytes to write
> + */
> +static inline void i3c_writel_fifo(void __iomem *addr, const void *buf,
> +				   int nbytes)
> +{
> +	writesl(addr, buf, nbytes / 4);
> +	if (nbytes & 3) {
> +		u32 tmp = 0;
> +
> +		memcpy(&tmp, buf + (nbytes & ~3), nbytes & 3);
> +		writel(tmp, addr);
> +	}
> +}
> +
> +/**
> + * i3c_readl_fifo - Read data buffer from 32bit FIFO
> + * @addr: FIFO Address to read from
> + * @buf: 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 *buf,
> +				  int nbytes)
> +{
> +	readsl(addr, buf, nbytes / 4);
> +	if (nbytes & 3) {
> +		u32 tmp;
> +
> +		tmp = readl(addr);
> +		memcpy(buf + (nbytes & ~3), &tmp, nbytes & 3);
> +	}
> +}
> +
>  #endif /* I3C_INTERNAL_H */
>
> --
> 2.49.0
>