Commit 91ec84f8 authored Feb 21, 2025 by Niklas Cassel

ata: libata-eh: Do not use ATAPI DMA for a device limited to PIO mode



atapi_eh_request_sense() currently uses ATAPI DMA if the SATA controller
has ATA_FLAG_PIO_DMA (PIO cmds via DMA) set.

However, ATA_FLAG_PIO_DMA is a flag that can be set by a low-level driver
on a port at initialization time, before any devices are scanned.

If a controller detects a connected device that only supports PIO, we set
the flag ATA_DFLAG_PIO.

Modify atapi_eh_request_sense() to not use ATAPI DMA if the connected
device only supports PIO.

Reported-by: Philip Pemberton <lists@philpem.me.uk>
Closes: https://lore.kernel.org/linux-ide/c6722ee8-5e21-4169-af59-cbbae9edc02f@philpem.me.uk/


Tested-by: Philip Pemberton <lists@philpem.me.uk>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20250221015422.20687-2-cassel@kernel.org


Signed-off-by: Niklas Cassel <cassel@kernel.org>

parent 08a04e20

drivers/ata/libata-eh.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -1542,8 +1542,15 @@ unsigned int atapi_eh_request_sense(struct ata_device *dev,
		tf.flags \|= ATA_TFLAG_ISADDR \| ATA_TFLAG_DEVICE;
		tf.command = ATA_CMD_PACKET;

		/* is it pointless to prefer PIO for "safety reasons"? */
		if (ap->flags & ATA_FLAG_PIO_DMA) {
		/*
		* Do not use DMA if the connected device only supports PIO, even if the
		* port prefers PIO commands via DMA.
		*
		* Ideally, we should call atapi_check_dma() to check if it is safe for
		* the LLD to use DMA for REQUEST_SENSE, but we don't have a qc.
		* Since we can't check the command, perhaps we should only use pio?
		*/
		if ((ap->flags & ATA_FLAG_PIO_DMA) && !(dev->flags & ATA_DFLAG_PIO)) {
		tf.protocol = ATAPI_PROT_DMA;
		tf.feature \|= ATAPI_PKT_DMA;
		} else {