Re: [PATCH] hwmon: xgene: access mailbox as RAM

[Hoan Tran]

On Fri, Sep 9, 2016 at 9:58 AM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> Hi Arnd,
>
> On Fri, Sep 09, 2016 at 05:38:58PM +0200, Arnd Bergmann wrote:
>> The newly added hwmon driver fails to build in an allmodconfig
>> kernel:
>>
>>       1  ERROR: "memblock_is_memory" [drivers/hwmon/xgene-hwmon.ko] undefined!
>>
>> According to comments in the code, the mailbox is a shared memory region,
>> not a set of MMIO registers, so we should use memremap() for mapping it
>> instead of ioremap or acpi_os_ioremap, and pointer dereferences instead
>> of readl/writel.
>>
>> The driver already uses plain kernel pointers, so it's a bit unusual
>> to work with functions that operate on __iomem pointers, and this
>> fixes that part too.
>>
>> I'm using READ_ONCE/WRITE_ONCE here to keep the existing behavior
>> regarding the ordering of the accesses from the CPU, but note that
>> there are no barriers (also unchanged from before).
>>
>> I'm also keeping the endianess behavior, though I'm unsure whether
>> the message data was supposed to be in LE32 format in the first
>> place, it's possible this was meant to be interpreted as a byte
>> stream instead.
>>
>> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
>>
>
> Thanks a lot for looking into this.
>
> I'll apply this patch to address the build problem. Much better than
> my rude "depends on BROKEN". It would be great to get a Tested-by:
> from someone with access to the hardware.
>

Hi Arnd and Guenter,

Thanks for the patch. I'm testing it out.

Hoan

> Guenter
>
>> diff --git a/drivers/hwmon/xgene-hwmon.c b/drivers/hwmon/xgene-hwmon.c
>> index bc78a5d10182..e834dfb3acca 100644
>> --- a/drivers/hwmon/xgene-hwmon.c
>> +++ b/drivers/hwmon/xgene-hwmon.c
>> @@ -34,7 +34,8 @@
>>  #include <linux/module.h>
>>  #include <linux/of.h>
>>  #include <linux/platform_device.h>
>> -#include <acpi/acpi_io.h>
>> +#include <linux/io.h>
>> +
>>  #include <acpi/pcc.h>
>>
>>  /* SLIMpro message defines */
>> @@ -126,10 +127,10 @@ static u16 xgene_word_tst_and_clr(u16 *addr, u16 mask)
>>  {
>>       u16 ret, val;
>>
>> -     val = readw_relaxed(addr);
>> +     val = le16_to_cpu(READ_ONCE(*addr));
>>       ret = val & mask;
>>       val &= ~mask;
>> -     writew_relaxed(val, addr);
>> +     WRITE_ONCE(*addr, cpu_to_le16(val));
>>
>>       return ret;
>>  }
>> @@ -137,7 +138,7 @@ static u16 xgene_word_tst_and_clr(u16 *addr, u16 mask)
>>  static int xgene_hwmon_pcc_rd(struct xgene_hwmon_dev *ctx, u32 *msg)
>>  {
>>       struct acpi_pcct_shared_memory *generic_comm_base = ctx->pcc_comm_addr;
>> -     void *ptr = generic_comm_base + 1;
>> +     u32 *ptr = (void*)(generic_comm_base + 1);
>>       int rc, i;
>>       u16 val;
>>
>> @@ -146,21 +147,21 @@ static int xgene_hwmon_pcc_rd(struct xgene_hwmon_dev *ctx, u32 *msg)
>>       ctx->resp_pending = true;
>>
>>       /* Write signature for subspace */
>> -     writel_relaxed(PCC_SIGNATURE_MASK | ctx->mbox_idx,
>> -                    &generic_comm_base->signature);
>> +     WRITE_ONCE(generic_comm_base->signature,
>> +                cpu_to_le32(PCC_SIGNATURE_MASK | ctx->mbox_idx));
>>
>>       /* Write to the shared command region */
>> -     writew_relaxed(MSG_TYPE(msg[0]) | PCCC_GENERATE_DB_INT,
>> -                    &generic_comm_base->command);
>> +     WRITE_ONCE(generic_comm_base->command,
>> +                cpu_to_le16(MSG_TYPE(msg[0]) | PCCC_GENERATE_DB_INT));
>>
>>       /* Flip CMD COMPLETE bit */
>> -     val = readw_relaxed(&generic_comm_base->status);
>> +     val = le16_to_cpu(READ_ONCE(generic_comm_base->status));
>>       val &= ~PCCS_CMD_COMPLETE;
>> -     writew_relaxed(val, &generic_comm_base->status);
>> +     WRITE_ONCE(generic_comm_base->status, cpu_to_le16(val));
>>
>>       /* Copy the message to the PCC comm space */
>>       for (i = 0; i < sizeof(struct slimpro_resp_msg) / 4; i++)
>> -             writel_relaxed(msg[i], ptr + i * 4);
>> +             WRITE_ONCE(ptr[i], cpu_to_le32(msg[i]));
>>
>>       /* Ring the doorbell */
>>       rc = mbox_send_message(ctx->mbox_chan, msg);
>> @@ -652,9 +653,9 @@ static int xgene_hwmon_probe(struct platform_device *pdev)
>>                */
>>               ctx->comm_base_addr = cppc_ss->base_address;
>>               if (ctx->comm_base_addr) {
>> -                     ctx->pcc_comm_addr =
>> -                                     acpi_os_ioremap(ctx->comm_base_addr,
>> -                                                     cppc_ss->length);
>> +                     ctx->pcc_comm_addr = memremap(ctx->comm_base_addr,
>> +                                                     cppc_ss->length,
>> +                                                     MEMREMAP_WT);
>>               } else {
>>                       dev_err(&pdev->dev, "Failed to get PCC comm region\n");
>>                       rc = -ENODEV;
>>