Anantha Subramanyam wrote:
This patch adds ATAPI DMA support for HT1000 (aka BCM5785) & HT1100
(aka BCM11000) SATA Controller.
Signed-off-by: Anantha Subramanyam <[EMAIL PROTECTED]>
Thanks much for your patience. Feedback:
Engineering process issues:
1) patch is word-wrapped, and cannot be applied by automatic tools. In
Linux, email is second only to the C compiler as a tool critical to
development work. It might take some time to get things set up
correctly -- but that's a one-time cost.
2) several occurences of "whitespace mangling": tabs were converted to
spaces, again making our automated tools unable to apply the patch.
Consistency (with other Linux drivers) issues:
1) avoid C++ comments. The rest of the driver exclusively uses /* style
(and 95% of the rest of the kernel does too). You should follow the
existing coding style whenever modifying existing code.
2) don't define a struct twice, once for each endian
(_k2_sata_cmd_desc_s). We use a very specific style, which the "sparse"
source code checking tool knows and checks:
a) define a single version of the struct
b) use C types that indicate endianness: __le32, __be16, etc.
c) in the source code, add endian conversions:
foo->prd_tbl_base_lo = cpu_to_le32(address);
These endian conversions are automatically optimized out
on like-endian platforms, and are heavily optimized on
unlike-endian platforms.
3) use POSIX-style struct definitions:
OK:
struct foo {
...
};
Not OK:
typedef struct _foo {
...
} foo_t;
4) avoid what we call "StudlyCaps" :) The preferred Linux style used in
the vast majority of code is lower case, with underscores separating words:
OK:
prd_tbl_hi
prd_cnt
prd_tbl_lo
Not OK:
sl_PrdTblBaseLow
sw_PrdCount
sw_PrdTblBaseHigh
5) similarly, avoid Hungarian notation, where the type is indicated in
the variable/member name.
OK: prd_tbl_lo
Not OK: sl_prd_tbl_lo
6) No need to add an extra indentation level after a 'return' statement:
static int k2_sata_check_atapi_dma(struct ata_queued_cmd *qc) { + u8
command = qc->scsicmd->cmnd[0]; + if (qc->ap->flags &
K2_FLAG_NO_ATAPI_DMA) return -1; /* ATAPI DMA not supported */ + else
+ {
7) static inline functions are preferred over cpp macros, because they
are far more type-safe.
+#define K2_IS_SATA_STS_GOOD(sata_sts) \ + (((sata_sts &
K2_SATA_DET_MASK) == K2_DEV_DET_PHY_RDY) && (((sata_sts &
K2_SATA_INTF_MASK)>>8) == K2_SATA_INFT_ACTIVE))
The C compiler is smart enough to ensure there is no penalty for using a
function rather than a macro.
8) in k2_ht1x_port_start(), use the standard Linux 'goto unwind' method
of error handling:
pspi = kmalloc(sizeof(k2_sata_port_info), GFP_KERNEL);
if (!pspi)
goto err_out;
pspi->pcmd_desc = dma_alloc_coherent(dev, ...);
if (!pspi->pcmd_desc)
goto err_out_pspi;
pspi->pcdb_cpybuf = dma_alloc_coherent(dev, ...);
if (!pspi->pcdb_cpybuf)
goto err_out_pcmd;
/* ... etc ... */
return 0;
err_out_pcmd:
dma_free_coherent(pspi->pcmd_desc);
err_out_pspi:
kfree(pspi);
err_out:
return rc;
9) don't add unnecessary casts from a void pointer:
k2_sata_port_info* pspi = (k2_sata_port_info*)ap->private_data;
10) remove redundant comment... by definition this statement is always
true, since your patch will be merged into a kernel later than 2.6.18.
+/*
+later version of libata (kernel 2.6.18 & later) have a elaborate
+error handling mech that includes multilevel of resets (soft, hard,
post...)
+so we plug into that
+
+*/
11) K2_SATA_WAIT_MDIO_DONE() should be a function, not a macro
12) overall, make sure your patch passes 'sparse' (see
Documentation/sparse.txt) and 'checkpatch' (see scripts/checkpatch.pl)
checks before submission. There are other minor issues I did not bother
to outline here.
Operational issues:
1) Use of 'volatile' is almost always the wrong thing to do:
int k2_ht1x_qdma_pause(struct ata_port *ap, int pause)
+{
+ k2_sata_port_info* pspi = (k2_sata_port_info*)ap->private_data;
+ u32 qsr;
+ volatile int i = 0;
In Linux, if you feel you need 'volatile', then really you most likely
need (a) to remove it, (b) to use a barrier(), or (c) use a spinlock.
'volatile' across SMP machines is rather useless, and ill-defined in the
C specifications.
2) remove redundant initialization of static var. Static variables are,
by definition, initialized to zero. Explicit initialization simply
wastes space in the initialized variable area.
- static int printed_version;
+ static int printed_version = 0;
3) we try _very_ hard to avoid all dependencies on the state produced by
BIOS. The three main reasons:
a) the driver may be used on non-x86 platforms, where
x86 BIOS code simply cannot be executed
b) during suspend/resume, the driver must be able to
initialize the controller fully after transition
from PCI D3 to PCI D0
c) PCI controller hotplug
Thus, I would like to avoid the need for the 'skip_init' module
parameter. Users and automated Linux install tools will be completely
unaware of skip_init, and will not have enough knowledge to use it. It
is best to simply Do The Right Thing in all cases.
4) don't use udelay/mdelay when you can sleep:
+inline void k2_lnx_sleep( u32 usec_delay)
+{
+ (usec_delay > 1000) ? mdelay(usec_delay/1000 + 1):
udelay(usec_delay);
+}
5) is it reasonable to use QDMA for ATA also?
6) use spin_lock() rather than spin_lock_irqsave() in
k2_ht1x_interrupt(). You're not competing with other interrupts AFAICS.
7) in k2_ht1x_qdma_intr(), ap->hsm_task_state generally refers to PIO
state. ditto for the use of ata_hsm_move() in k2_ht1x_handle_qdma_error().
Can you explain the need, there?
It is more likely that you should override ->qc_issue and handle things
at a top level, rather than overriding specific pieces of the ATAPI host
state machine. The HSM was not really designed to be overridden piecemeal.
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