Re: [PATCH v3 14/15] ata: ahci: add shutdown helpers for AHCI controllers

["Sascha Hauer" <s.hauer@pengutronix.de>]

On 2026-08-02 15:16, Luca Lauro via B4 Relay wrote:
> From: Luca Lauro <famlauro93l@gmail.com>
> 
> Introduce helper functions to stop the DMA engine and FIS receive engine
> before shutdown. These helpers mirror the libata shutdown sequence and
> ensure that no AHCI activity is in progress when the system powers off.
> 
> Signed-off-by: Luca Lauro <famlauro93l@gmail.com>
> ---
>  drivers/ata/ahci.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 60 insertions(+)
> 
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index a9a3f43f21..e9e73069c1 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -21,6 +21,7 @@
>  #include <linux/sizes.h>
>  #include <linux/pci.h>
>  #include <clock.h>
> +#include <poweroff.h>
>  
>  #include "ahci.h"
>  
> @@ -683,6 +684,65 @@ static int ahci_probe(struct device *dev)
>  	return ret;
>  }
>  
> +/* -------------------------------- */
> +/*		AHCI shutdown helpers		*/
> +/* -------------------------------- */
> +
> +/* Stop DMA engine (clear START, wait LIST_ON=0) */
> +static int ahci_stop_engine(struct ahci_port *port)
> +{
> +	u32 cmd;
> +
> +	cmd = ahci_port_read(port, PORT_CMD);
> +
> +	/* Already stopped? */
> +	if (!(cmd & (PORT_CMD_START | PORT_CMD_LIST_ON)))
> +		return 0;
> +
> +	/* Clear START */
> +	cmd &= ~PORT_CMD_START;
> +	ahci_port_write_f(port, PORT_CMD, cmd);
> +
> +	/* Wait for LIST_ON to clear */
> +	return wait_on_timeout(500 * MSECOND,
> +		!(ahci_port_read(port, PORT_CMD) & PORT_CMD_LIST_ON));
> +}
> +
> +/* Stop FIS receive engine (clear FIS_RX, wait FIS_ON=0) */
> +static int ahci_stop_fis_rx(struct ahci_port *port)
> +{
> +	u32 cmd;
> +
> +	cmd = ahci_port_read(port, PORT_CMD);
> +	cmd &= ~PORT_CMD_FIS_RX;
> +	ahci_port_write_f(port, PORT_CMD, cmd);
> +
> +	/* Wait for FIS_ON to clear */
> +	return wait_on_timeout(1000 * MSECOND,
> +		!(ahci_port_read(port, PORT_CMD) & PORT_CMD_FIS_ON));
> +}
> +
> +/* Stop all ports (libata_pci_shutdown_one equivalent) */
> +static void __maybe_unused ahci_shutdown_host(struct ahci_device *ahci)
> +{
> +	int i, n_ports;
> +
> +	n_ports = max_t(int, ahci->n_ports, fls(ahci->port_map));
> +
> +	for (i = 0; i < n_ports; i++) {
> +		struct ahci_port *port = &ahci->ports[i];
> +
> +		if (!(ahci->port_map & (1 << i)))
> +			continue;
> +
> +		/* Stop DMA engine */
> +		ahci_stop_engine(port);
> +
> +		/* Stop FIS receive engine */
> +		ahci_stop_fis_rx(port);
> +	}
> +}

This only adds unused code. If this is used in another patch, please
move it there.

Sascha

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