linux-kernel - [PATCH 1/6] pata_cypress: add a module option to disable BM-DMA

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Date:   Wed, 16 Jun 2021 15:46:53 +0200
From:   Christoph Hellwig <hch@....de>
To:     "David S. Miller" <davem@...emloft.net>,
        Jens Axboe <axboe@...nel.dk>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-ide@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-alpha@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-m68k@...ts.linux-m68k.org
Subject: [PATCH 1/6] pata_cypress: add a module option to disable BM-DMA

Multiple users report that they need to disable DMA on this driver,
so provide an option to do so without affecting all of libata.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/ata/pata_cypress.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/pata_cypress.c b/drivers/ata/pata_cypress.c
index e1486fe298ae..5b3a7a8ebef6 100644
--- a/drivers/ata/pata_cypress.c
+++ b/drivers/ata/pata_cypress.c
@@ -41,6 +41,10 @@ enum {
 	CY82_INDEX_TIMEOUT	= 0x32
 };
 
+static bool enable_dma = true;
+module_param(enable_dma, bool, 0);
+MODULE_PARM_DESC(enable_dma, "Enable bus master DMA operations");
+
 /**
  *	cy82c693_set_piomode	-	set initial PIO mode data
  *	@ap: ATA interface
@@ -124,14 +128,16 @@ static struct ata_port_operations cy82c693_port_ops = {
 
 static int cy82c693_init_one(struct pci_dev *pdev, const struct pci_device_id *id)
 {
-	static const struct ata_port_info info = {
+	static struct ata_port_info info = {
 		.flags = ATA_FLAG_SLAVE_POSS,
 		.pio_mask = ATA_PIO4,
-		.mwdma_mask = ATA_MWDMA2,
 		.port_ops = &cy82c693_port_ops
 	};
 	const struct ata_port_info *ppi[] = { &info, &ata_dummy_port_info };
 
+	if (enable_dma)
+		info.mwdma_mask = ATA_MWDMA2;
+
 	/* Devfn 1 is the ATA primary. The secondary is magic and on devfn2.
 	   For the moment we don't handle the secondary. FIXME */
 
-- 
2.30.2