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authorMaciej W. Rozycki <macro@orcam.me.uk>2023-01-09 00:56:52 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-01-20 15:12:00 +0300
commit6640727fc55b7f0b561e927bc9c5b9d4c459fd8e (patch)
tree963db3fe3b386c4d35e5ddf573c15e7426ea1f33
parentf01dda1cb85e14a1d51c3cedad0feaaf71a93b4b (diff)
downloadlinux-6640727fc55b7f0b561e927bc9c5b9d4c459fd8e.tar.xz
parport_pc: Let chipset drivers mask ECR bits on writes
Provide an `ecr_writable' parameter to `__parport_pc_probe_port' so that callers can specify a mask of bits to modify on ECR writes. To avoid the need for separate bit set and bit clear masks always set bit 0 whenever a non-zero mask has been set, as all the currently known cases where a mask is required, that is Oxford Semiconductor devices, do require this bit to be set. If further cases are discovered where the bit is required to be clear, we can update code accordingly, but chances are very low as the bit is supposed to be read-only[1]. Skip ECR probing, which can be problematic as the Oxford Semiconductor OX12PCI840 part has been reported to lock up on setting bit 2, whenever a non-zero mask has been requested by a port subdriver, assuming that the ECR must be there if the subdriver has requested a specific way to access it. References: [1] "Extended Capabilities Port Protocol and ISA Interface Standard", Microsoft Corporation, Revision: 1.14, July 14, 1993, Table 14 "Extended Control Register" Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk> Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com> Link: https://lore.kernel.org/r/20230108215656.6433-3-sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/parport/parport_pc.c46
-rw-r--r--include/linux/parport_pc.h3
2 files changed, 32 insertions, 17 deletions
diff --git a/drivers/parport/parport_pc.c b/drivers/parport/parport_pc.c
index 9daaaaa305e6..ad49fd356c7b 100644
--- a/drivers/parport/parport_pc.c
+++ b/drivers/parport/parport_pc.c
@@ -106,15 +106,22 @@ static int pnp_registered_parport;
static void frob_econtrol(struct parport *pb, unsigned char m,
unsigned char v)
{
+ const struct parport_pc_private *priv = pb->physport->private_data;
+ unsigned char ecr_writable = priv->ecr_writable;
unsigned char ectr = 0;
+ unsigned char new;
if (m != 0xff)
ectr = inb(ECONTROL(pb));
- pr_debug("frob_econtrol(%02x,%02x): %02x -> %02x\n",
- m, v, ectr, (ectr & ~m) ^ v);
+ new = (ectr & ~m) ^ v;
+ if (ecr_writable)
+ /* All known users of the ECR mask require bit 0 to be set. */
+ new = (new & ecr_writable) | 1;
- outb((ectr & ~m) ^ v, ECONTROL(pb));
+ pr_debug("frob_econtrol(%02x,%02x): %02x -> %02x\n", m, v, ectr, new);
+
+ outb(new, ECONTROL(pb));
}
static inline void frob_set_mode(struct parport *p, int mode)
@@ -1479,21 +1486,24 @@ static int parport_ECR_present(struct parport *pb)
struct parport_pc_private *priv = pb->private_data;
unsigned char r = 0xc;
- outb(r, CONTROL(pb));
- if ((inb(ECONTROL(pb)) & 0x3) == (r & 0x3)) {
- outb(r ^ 0x2, CONTROL(pb)); /* Toggle bit 1 */
+ if (!priv->ecr_writable) {
+ outb(r, CONTROL(pb));
+ if ((inb(ECONTROL(pb)) & 0x3) == (r & 0x3)) {
+ outb(r ^ 0x2, CONTROL(pb)); /* Toggle bit 1 */
- r = inb(CONTROL(pb));
- if ((inb(ECONTROL(pb)) & 0x2) == (r & 0x2))
- goto no_reg; /* Sure that no ECR register exists */
- }
+ r = inb(CONTROL(pb));
+ if ((inb(ECONTROL(pb)) & 0x2) == (r & 0x2))
+ /* Sure that no ECR register exists */
+ goto no_reg;
+ }
- if ((inb(ECONTROL(pb)) & 0x3) != 0x1)
- goto no_reg;
+ if ((inb(ECONTROL(pb)) & 0x3) != 0x1)
+ goto no_reg;
- ECR_WRITE(pb, 0x34);
- if (inb(ECONTROL(pb)) != 0x35)
- goto no_reg;
+ ECR_WRITE(pb, 0x34);
+ if (inb(ECONTROL(pb)) != 0x35)
+ goto no_reg;
+ }
priv->ecr = 1;
outb(0xc, CONTROL(pb));
@@ -2005,7 +2015,8 @@ static struct parport *__parport_pc_probe_port(unsigned long int base,
int irq, int dma,
struct device *dev,
int irqflags,
- unsigned int mode_mask)
+ unsigned int mode_mask,
+ unsigned char ecr_writable)
{
struct parport_pc_private *priv;
struct parport_operations *ops;
@@ -2054,6 +2065,7 @@ static struct parport *__parport_pc_probe_port(unsigned long int base,
priv->ctr = 0xc;
priv->ctr_writable = ~0x10;
priv->ecr = 0;
+ priv->ecr_writable = ecr_writable;
priv->fifo_depth = 0;
priv->dma_buf = NULL;
priv->dma_handle = 0;
@@ -2256,7 +2268,7 @@ struct parport *parport_pc_probe_port(unsigned long int base,
int irqflags)
{
return __parport_pc_probe_port(base, base_hi, irq, dma,
- dev, irqflags, 0);
+ dev, irqflags, 0, 0);
}
EXPORT_SYMBOL(parport_pc_probe_port);
diff --git a/include/linux/parport_pc.h b/include/linux/parport_pc.h
index 3d6fc576d6a1..f1ec5c10c3b3 100644
--- a/include/linux/parport_pc.h
+++ b/include/linux/parport_pc.h
@@ -26,6 +26,9 @@ struct parport_pc_private {
/* Whether or not there's an ECR. */
int ecr;
+ /* Bitmask of writable ECR bits. */
+ unsigned char ecr_writable;
+
/* Number of PWords that FIFO will hold. */
int fifo_depth;