Aero controllers support balanced performance mode through the ability to
configure queues with different properties.

Reply queues with interrupt coalescing enabled are called "high iops reply
queues" and reply queues with interrupt coalescing disabled are called "low
latency reply queues".

The driver configures a combination of high iops and low latency reply
queues if:

 - HBA is an AERO controller;

 - MSI-X vectors supported by the HBA is 128;

 - Total CPU count in the system more than high iops queue count;

 - Driver is loaded with default max_msix_vectors module parameter; and

 - System booted in non-kdump mode.
Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Added driver support to allow passthrough MPI toolbox type MFI commands to
firmware based on firmware capability.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

For RAID5/RAID6 volumes configured behind Aero, driver will be doing 64bit
division operations on behalf of firmware as controller's ARM CPU is very
slow in this division. Later, driver calculates Q-ARM, P-ARM and Log-ARM and
passes those values to firmware by writing these values to RAID_CONTEXT.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

RAID1 PCI bandwidth limit algorithm is not applicable to Aero as it's PCIe
Gen4 adapter.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Issue: This issue is applicable to scenario when JBOD sequence map is
unavailable (memory allocation for JBOD sequence map failed) to driver but
feature is supported by firmware.  If the driver sends a JBOD IO by not
adding 255 (MAX_PHYSICAL_DEVICES - 1) to device ID when underlying firmware
supports JBOD sequence map, it will lead to the IO failure.

Fix: For JBOD IOs, driver will not use the RAID map to fetch the devhandle
if JBOD sequence map is unavailable. Driver will set Devhandle to 0xffff
and Target ID to 'device ID + 255 (MAX_PHYSICAL_DEVICES - 1)'.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Firmware does not expect FastPath IO sent through Region Lock Bypass queue.
Though firmware never exposes such settings when fastpath IO can be sent to
RL bypass queue but it's safer to remove dead code which directs fastpath
IO to RL Bypass queue.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Issue: Under certain conditions, controller goes in FAULT state after IOC
INIT fired to firmware. Such Fault can be recovered through controller
reset.

Fix: In driver probe context, if firmware fault is observed post IOC INIT,
driver would do controller reset followed by retry logic for IOC INIT
command.
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Issue: There is possibility of few DCMDs timing out with 'reset_mutex' lock
held. As part of DCMD timeout handling, driver calls function
megasas_reset_fusion which also tries to acquire same lock 'reset_mutex'
and end up with deadlock.

Fix: Upon timeout of DCMDs (which are fired with 'reset_mutex' lock held),
driver will release 'reset_mutex' before calling OCR function and will
acquire lock again after OCR function returns.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

On PowerPC architecture, calling disable_irq_nosync from IRQ context is not
providing the required effect.

In current megaraid_sas driver, disable_irq_nosync is being called from IRQ
context before enabling IRQ poll. But due to the issue seen on PPC, after
IRQ poll disable and legacy ISR is enabled, we are not seeing our ISR
getting called.

Fix: Call disable_irq from IRQ poll thread context instead of IRQ context.
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

This patch will add support for non-secure Aero adapter PCI IDs.  Driver
will throw an error message when a non-secure type controller is
detected. Purpose of this interface is to avoid interacting with any
firmware which is not secured/signed by Broadcom. Any tampering on Firmware
component will be detected by hardware and it will be communicated to the
driver to avoid any further interaction with that component.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Aero adapters provides Atomic Request Descriptor as an alternative method
for posting an entry onto a request queue. The posting of an Atomic Request
Descriptor is an atomic operation, providing a safe mechanism for multiple
processors on the host to post requests without synchronization. This
Atomic Request Descriptor format is identical to first 32 bits of Default
Request Descriptor and uses only 32 bits.

If Aero adapters support Atomic descriptor, driver should use it for
posting IOs and DCMDs to firmware.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Added the logic for collecting IOP log respective to event log size.
Signed-off-by: Deepak Ukey <deepak.ukey@microchip.com>
Signed-off-by: Viswas G <Viswas.G@microchip.com>
Reviewed-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Added support to read event log size from MPI configuration table and
export through sysfs.
Signed-off-by: Deepak Ukey <deepak.ukey@microchip.com>
Signed-off-by: Viswas G <Viswas.G@microchip.com>
Reviewed-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Enable msix load balance only when combined reply queue mode is disabled on
the SAS3 and above generation HBA devices.

Earlier msix load balance used to enable if the number of online cpus is
greater than the number of MSI-X vectors enabled on the HBA.  Combined reply
queue mode will be disabled only on those HBA which works in shared
resources mode. I.e. on SAS3 HBAs it will be <= 8 and on SAS35 HBA devices
it will be <= 16.

 - Before this patch if system has 256 logical CPUs and HBA exposes 128
   MSI-X vectors, driver will enable msix load balance.

 - After this patch if system has 256 logical CPUs and HBA exposes 128
   MSI-X vectors, driver will disable msix load balance.

 - After this patch if system has 256 logical CPUs and HBA exposes 16 MSI-X
   vectors (due to combined reply queue mode being off in HW), driver will
   enable msix load balance.
Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Even though 'smp_affinity_enable' module parameter is enabled, if the
number of online CPUs is bigger than the number of msix vectors enabled on
that HBA, then smp affinity settings should be disabled only for this HBA.

But currently the smp affinity setting is disabled globally and hence smp
affinity will be disabled for subsequent HBAs even though number of msix
vectors enabled for this HBA matches the number of online CPU.

To fix this, define a per HBA variable smp_affinity_enable.  Initially this
variable is initialized with smp_affinity_enable module parameter value. If
this HBA has less number of msix vectors configured when compared to number
of online cpus, then only this HBA's variable smp_affinity_enable is set to
zero.
Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

When enabling high iops queues, the driver should use the HBA's configured
PCIe link speed instead of looking for the maximum link speed.

I.e. enable high iops queues only if Aero/Sea HBA's configured PCIe link
speed is set to 16GT/s.
Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Currently default perf_mode is set to 'balanced' on Intel architecture
machines and on other machines default perf_mode is set to 'latency' mode.

This CPU architecture check is removed and the default perf_mode mode is
set to 'balanced' mode on all machines.

User can choose the required performance mode using perf_mode module
parameter.
Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

The ufs-tool stable release v1.0 is available at:

	https://github.com/westerndigitalcorporation/ufs-tool

Feedback and bug reports, as always, are welcomed.
Signed-off-by: Arthur Simchaev <Arthur.Simchaev@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

If cb_arg alloc failed, we can't release the struct orig_io_req refcount
before we take its refcount. As Saurav said, move the srr_err label down
to avoid unnecessary refcount release and nullptr free.
Signed-off-by: Lin Yi <teroincn@163.com>
Acked-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

If cb_arg alloc failed, we can't release the struct orig_io_req refcount
before we take its refcount. As Saurav said, move the rec_err label down
to avoid unnecessary refcount release and nullptr free.
Signed-off-by: Lin Yi <teroincn@163.com>
Acked-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Update the driver version to 2.12.10.
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

 - Reduce the sg_tablesize to 255.

 - Reduce the MAX BDs firmware can handle to 255.

 - Return IO to ML if BD goes more then 255 after split.

 - Correct the size of each BD split to 0xffff.
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

If firmware sends either cleanup or abort completion, it means other won't
be sent. Clean out flags for other as well.
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Separate out abort and cleanup flag and completion, to have better
understaning of what is getting processed.
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

In certain tests where the SCSI error handler issues an abort that is
already outstanding, we will cleanup the command so that the SCSI error
handler can proceed.  In some of these cases we were seeing a command
mismatch:

 kernel: scsi host2: bnx2fc: xid:0x42b eh_abort - refcnt = 2
 kernel: bnx2fc: eh_abort: io_req (xid = 0x42b) already in abts processing
 kernel: scsi host2: bnx2fc: xid:0x42b Entered bnx2fc_initiate_cleanup
 kernel: scsi host2: bnx2fc: xid:0x42b CLEANUP io_req xid = 0x80b
 kernel: scsi host2: bnx2fc: xid:0x80b cq_compl- cleanup resp rcvd
 kernel: scsi host2: bnx2fc: xid:0x42b complete - rx_state = 9
 kernel: scsi host2: bnx2fc: xid:0x42b Entered process_cleanup_compl refcnt = 2, cmd_type = 1
 kernel: scsi host2: bnx2fc: xid:0x42b scsi_done. err_code = 0x7
 kernel: scsi host2: bnx2fc: xid:0x42b sc=ffff8807f93dfb80, result=0x7, retries=0, allowed=5
 kernel: ------------[ cut here ]------------
 kernel: WARNING: at /root/rpmbuild/BUILD/netxtreme2-7.14.43/obj/default/bnx2fc-2.12.1/driver/bnx2fc_io.c:1347 bnx2fc_eh_abort+0x56f/0x680 [bnx2fc]()
 kernel: xid=0x42b refcount=-1
 kernel: Modules linked in:
 kernel: nls_utf8 isofs sr_mod cdrom tcp_lp dm_round_robin xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 tun bridge ebtable_filter ebtables fuse ip6table_filter ip6_tables iptable_filter bnx2fc(OE) cnic(OE) uio fcoe libfcoe 8021q libfc garp mrp scsi_transport_fc stp llc scsi_tgt vfat fat dm_service_time intel_powerclamp coretemp intel_rapl iosf_mbi kvm_intel kvm irqbypass crc32_pclmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd ses enclosure ipmi_ssif i2c_core hpilo hpwdt wmi sg ipmi_devintf pcspkr ipmi_si ipmi_msghandler shpchp acpi_power_meter dm_multipath nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs sd_mod crc_t10dif
 kernel: crct10dif_generic bnx2x(OE) crct10dif_pclmul crct10dif_common crc32c_intel mdio ptp pps_core libcrc32c smartpqi scsi_transport_sas fjes uas usb_storage dm_mirror dm_region_hash dm_log dm_mod
 kernel: CPU: 9 PID: 2012 Comm: scsi_eh_2 Tainted: G        W  OE  ------------   3.10.0-514.el7.x86_64 #1
 kernel: Hardware name: HPE Synergy 480 Gen10/Synergy 480 Gen10 Compute Module, BIOS I42 03/21/2018
 kernel: ffff8807f25a3d98 0000000015e7fa0c ffff8807f25a3d50 ffffffff81685eac
 kernel: ffff8807f25a3d88 ffffffff81085820 ffff8807f8e39000 ffff880801ff7468
 kernel: ffff880801ff7610 0000000000002002 ffff8807f8e39014 ffff8807f25a3df0
 kernel: Call Trace:
 kernel: [<ffffffff81685eac>] dump_stack+0x19/0x1b
 kernel: [<ffffffff81085820>] warn_slowpath_common+0x70/0xb0
 kernel: [<ffffffff810858bc>] warn_slowpath_fmt+0x5c/0x80
 kernel: [<ffffffff8168d842>] ? _raw_spin_lock_bh+0x12/0x50
 kernel: [<ffffffffa0549e6f>] bnx2fc_eh_abort+0x56f/0x680 [bnx2fc]
 kernel: [<ffffffff814570af>] scsi_error_handler+0x59f/0x8b0
 kernel: [<ffffffff81456b10>] ? scsi_eh_get_sense+0x250/0x250
 kernel: [<ffffffff810b052f>] kthread+0xcf/0xe0
 kernel: [<ffffffff810b0460>] ? kthread_create_on_node+0x140/0x140
 kernel: [<ffffffff81696418>] ret_from_fork+0x58/0x90
 kernel: [<ffffffff810b0460>] ? kthread_create_on_node+0x140/0x140
 kernel: ---[ end trace 42deb88f2032b111 ]---

The reason that there was a mismatch is that the SCSI command is actual
returned from the cleanup handler.  In previous testing, the type of
cleanup notification we'd get from the CQE did not trigger the code that
returned the SCSI command.  To overcome the previous behavior we would put
a reference in bnx2fc_abts_cleanup() to account for the SCSI command.
However, in cases where the SCSI command is actually off, we end up with an
extra put.

The fix for this is to only take the extra put in bnx2fc_abts_cleanup if
the completion for the cleanup times out.
Signed-off-by: Chad Dupuis <cdupuis@marvell.com>
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

For bnx2fc, the source FCoE MAC is stored in the fcoe_port struct in the
data_src_mac field.  Currently this is set in fcoe_ctlr_recv_flogi which
ends up setting it by simply using fc_fcoe_set_mac() which only uses the
default FCF-MAC.  We still want to store the source FCoE MAC in
port->data_src_mac but we want to snoop the FLOGI response payload so as to
set it in the following method:

1. If a granted_mac is found, use that.

2. If not granted_mac is there but there is a FCF-MAP from the FCF then
   create the MAC from the FCF-MAP and the destination ID from the frame.

3. If there is no FCF-MAP the use the spec. default FCF-MAP and the
   destination ID from the frame.
Signed-off-by: Chad Dupuis <cdupuis@marvell.com>
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Add more Intel PCI IDs.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

In the case of UPIU/DME request execution failed in UFS device,
ufs_bsg_request() will complete the failed bsg job by calling
bsg_job_done(). Meanwhile, it returns this error status to blk-mq layer,
then triggers blk-mq completing this request again, this will cause the
following panic.

Call trace:
ll_sc___cmpxchg_case_acq_32+0x4/0x20
complete+0x28/0x70
blk_end_sync_rq+0x24/0x30
blk_mq_end_request+0xb8/0x118
bsg_job_put+0x4c/0x58
bsg_complete+0x20/0x30
blk_done_softirq+0xb4/0xe8
do_softirq+0x154/0x3f0
run_ksoftirqd+0x4c/0x68
smpboot_thread_fn+0x22c/0x268
kthread+0x130/0x138
ret_from_fork+0x10/0x1c
Code: f84107fe d65f03c0 d503201f f9800011 (885ffc10)
---[ end trace d92825bff6326e66 ]---
Kernel panic - not syncing: Fatal exception in interrupt

This patch is to fix this issue. The solution is to complete the ufs-bsg
job only if no error happened.

[mkp: commit description tweak]

Fixes: df032bf2 (scsi: ufs: Add a bsg endpoint that supports UPIUs)
Signed-off-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Correct dev_dbg to dev_err, so as to print out the error information in
case of DME command failed.
Signed-off-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

The 'affinity_hint_set' is not used any longer since commit
0d9f0a52 ("virtio_scsi: use virtio IRQ affinity").
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Use existing macros.  No functional change.

[mkp: typo]
Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Acked-by: Suganath Prabu <suganath-prabu.subramani@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Support is easier with all driver parameters visible in sysfs.  Also I've
replaced a constant with an octal permission.
Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Acked-by: Suganath Prabu <suganath-prabu.subramani@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

New Qualcomm AArch64 based laptops are now available which use UFS as their
primary data storage medium.  These devices are supplied with ACPI support
out of the box.  This patch ensures the Qualcomm UFS driver will be bound
when the "QCOM24A5" H/W device is advertised as present.
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with
memory for some number of elements for that array. For example:

struct MR_PD_CFG_SEQ_NUM_SYNC {
	...
        struct MR_PD_CFG_SEQ seq[1];
} __packed;

Make use of the struct_size() helper instead of an open-coded version in
order to avoid any potential type mistakes.

So, replace the following form:

sizeof(struct MR_PD_CFG_SEQ_NUM_SYNC) + (sizeof(struct MR_PD_CFG_SEQ) * (MAX_PHYSICAL_DEVICES - 1))

with:

struct_size(pd_sync, seq, MAX_PHYSICAL_DEVICES - 1)

This code was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

A system bus error during a PDMA send operation can result in bytes being
lost. Theoretically that could cause the target to remain in DATA OUT phase
and the initiator (expecting a phase change) would time-out waiting for the
Last Byte Sent flag. Should that happen, fail the transfer so the core
driver will stop using PDMA with this target.

Cc: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Add support for Apple's custom "SCSI DMA" chip. This patch doesn't make use
of its DMA capability. Just the PDMA capability is sufficient to improve
sequential read throughput by a factor of 5.

Cc: Michael Schmitz <schmitzmic@gmail.com>
Cc: Joshua Thompson <funaho@jurai.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

A system bus error during a PDMA transfer can mess up the calculation of
the transfer residual (the PDMA handshaking hardware lacks a byte
counter). This results in data corruption.

The algorithm in this patch anticipates a bus error by starting each
transfer with a MOVE.B instruction. If a bus error is caught the transfer
will be retried. If a bus error is caught later in the transfer (for a
MOVE.W instruction) the transfer gets failed and subsequent requests for
that target will use PIO instead of PDMA.

This avoids the "!REQ and !ACK" error so the severity level of that message
is reduced to KERN_DEBUG.

Cc: Michael Schmitz <schmitzmic@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@vger.kernel.org # v4.14+
Fixes: 3a0f64bf ("mac_scsi: Fix pseudo DMA implementation")
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reported-by: Chris Jones <chris@martin-jones.com>
Tested-by: Stan Johnson <userm57@yahoo.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Some targets introduce delays when handshaking the response to certain
commands. For example, a disk may send a 96-byte response to an INQUIRY
command (or a 24-byte response to a MODE SENSE command) too slowly.

Apparently the first 12 or 14 bytes are handshaked okay but then the system
bus error timeout is reached while transferring the next word.

Since the scsi bus phase hasn't changed, the driver then sets the target
borken flag to prevent further PDMA transfers. The driver also logs the
warning, "switching to slow handshake".

Raise the PDMA threshold to 512 bytes so that PIO transfers will be used
for these commands. This default is sufficiently low that PDMA will still
be used for READ and WRITE commands.

The existing threshold (16 bytes) was chosen more or less at random.
However, best performance requires the threshold to be as low as possible.
Those systems that don't need the PIO workaround at all may benefit from
mac_scsi.setup_use_pdma=1

Cc: Michael Schmitz <schmitzmic@gmail.com>
Cc: stable@vger.kernel.org # v4.14+
Fixes: 3a0f64bf ("mac_scsi: Fix pseudo DMA implementation")
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>