Date:   Thu, 3 Oct 2019 17:37:23 +0000
From:   Sanjay R Mehta <sanmehta@....com>
To:     Vinod Koul <vkoul@...nel.org>
CC:     "Hook, Gary" <Gary.Hook@....com>,
        "S-k, Shyam-sundar" <Shyam-sundar.S-k@....com>,
        "Shah, Nehal-bakulchandra" <Nehal-bakulchandra.Shah@....com>,
        "Kumar, Rajesh" <Rajesh1.Kumar@....com>,
        "mchehab+samsung@...nel.org" <mchehab+samsung@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "robh@...nel.org" <robh@...nel.org>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>
Subject: Re: [PATCH 1/4] dma: Add PTDMA Engine driver support


On 9/25/2019 12:42 AM, Vinod Koul wrote:
> [CAUTION: External Email]
>
> On 24-09-19, 07:31, Mehta, Sanju wrote:
>> From: Sanjay R Mehta <sanju.mehta@....com>
>>
>> This is the driver for the AMD passthrough DMA Engine
> Please fix threading for your series, they are all over my inbox :(
This will be taken care in next version of patch set.
>
>> +#include "ptdma.h"
>> +
>> +/* Union to define the function field (cmd_reg1/dword0) */
>> +union pt_function {
>> +     struct {
>> +             u16 byteswap:2;
>> +             u16 bitwise:3;
>> +             u16 reflect:2;
>> +             u16 rsvd:8;
>> +     } pt;
>> +     u16 raw;
>> +};
> So IIUC you are using this to write to hw registers, what is wrong with
> defining bit fields for registers using BIT and GENMASK and then write
> the settings to the hardware. That IMHO looks much neater!
Agreed. This will be taken care in next version of patch set.
>
>> +static inline u32 low_address(unsigned long addr)
>> +{
>> +     return (u64)addr & 0x0ffffffff;
>> +}
>> +
>> +static inline u32 high_address(unsigned long addr)
>> +{
>> +     return ((u64)addr >> 32) & 0x00000ffff;
>> +}
> Use lower_32_bits() and upper_32_bits() please. Also check the APIs in
> kernel and don't invent your own!
Agreed. This will be taken care in next version of patch set.
>
>> +int pt_core_perform_passthru(struct pt_op *op)
>> +{
>> +     struct ptdma_desc desc;
>> +     union pt_function function;
>> +     struct pt_dma_info *saddr = &op->src.u.dma;
>> +
>> +     memset(&desc, 0, Q_DESC_SIZE);
>> +
>> +     PT_CMD_ENGINE(&desc) = PT_ENGINE_PASSTHRU;
>> +
>> +     PT_CMD_SOC(&desc) = 0;
>> +     PT_CMD_IOC(&desc) = 1;
>> +     PT_CMD_INIT(&desc) = 0;
>> +     PT_CMD_EOM(&desc) = op->eom;
>> +     PT_CMD_PROT(&desc) = 0;
>> +
>> +     function.raw = 0;
>> +     PT_BYTESWAP(&function) = op->passthru.byte_swap;
>> +     PT_BITWISE(&function) = op->passthru.bit_mod;
>> +     PT_CMD_FUNCTION(&desc) = function.raw;
>> +
>> +     PT_CMD_LEN(&desc) = saddr->length;
>> +
>> +     PT_CMD_SRC_LO(&desc) = pt_addr_lo(&op->src.u.dma);
>> +     PT_CMD_SRC_HI(&desc) = pt_addr_hi(&op->src.u.dma);
>> +     PT_CMD_SRC_MEM(&desc) = PT_MEMTYPE_SYSTEM;
>> +
>> +     PT_CMD_DST_LO(&desc) = pt_addr_lo(&op->dst.u.dma);
>> +     PT_CMD_DST_HI(&desc) = pt_addr_hi(&op->dst.u.dma);
>> +     PT_CMD_DST_MEM(&desc) = PT_MEMTYPE_SYSTEM;
> This really looks bad, as I siad please use bits and genmasks. Also see
> how other driver handles registers transparently!
Agreed. This will be taken care in next version of patch set.
>
>> +static irqreturn_t pt_core_irq_handler(int irq, void *data)
>> +{
>> +     struct pt_device *pt = (struct pt_device *)data;
>> +
>> +     pt_core_disable_queue_interrupts(pt);
>> +     tasklet_schedule(&pt->irq_tasklet);
> Why are you not submitting txn in ISR, you are keeping dmaengine idle
> for tasklet!
Agreed. This will be taken care in next version of patch set.
>
>> +     cmd_q->qidx = 0;
>> +     /* Preset some register values and masks that are queue
>> +      * number dependent
>> +      */
> kernel style is
> /*
>  * this is a multi line comment
>  * notice first and last line
>  */
>
>> +     cmd_q->reg_control = pt->io_regs + CMD_Q_STATUS_INCR;
>> +     cmd_q->reg_tail_lo = cmd_q->reg_control + CMD_Q_TAIL_LO_BASE;
>> +     cmd_q->reg_head_lo = cmd_q->reg_control + CMD_Q_HEAD_LO_BASE;
>> +     cmd_q->reg_int_enable = cmd_q->reg_control +
>> +                             CMD_Q_INT_ENABLE_BASE;
>> +     cmd_q->reg_interrupt_status = cmd_q->reg_control +
>> +                                   CMD_Q_INTERRUPT_STATUS_BASE;
>> +     cmd_q->reg_status = cmd_q->reg_control + CMD_Q_STATUS_BASE;
>> +     cmd_q->reg_int_status = cmd_q->reg_control +
>> +                             CMD_Q_INT_STATUS_BASE;
>> +     cmd_q->reg_dma_status = cmd_q->reg_control +
>> +                             CMD_Q_DMA_STATUS_BASE;
>> +     cmd_q->reg_dma_read_status = cmd_q->reg_control +
>> +                                  CMD_Q_DMA_READ_STATUS_BASE;
>> +     cmd_q->reg_dma_write_status = cmd_q->reg_control +
>> +                                   CMD_Q_DMA_WRITE_STATUS_BASE;
>> +
>> +     init_waitqueue_head(&cmd_q->int_queue);
>> +
>> +     dev_dbg(dev, "queue available\n");
> Noise
This will be taken care in next version of patch set.
>
>> +
>> +     /* Turn off the queues and disable interrupts until ready */
>> +     pt_core_disable_queue_interrupts(pt);
>> +
>> +     cmd_q->qcontrol = 0; /* Start with nothing */
>> +     iowrite32(cmd_q->qcontrol, cmd_q->reg_control);
>> +
>> +     ioread32(cmd_q->reg_int_status);
>> +     ioread32(cmd_q->reg_status);
>> +
>> +     /* Clear the interrupt status */
>> +     iowrite32(SUPPORTED_INTERRUPTS, cmd_q->reg_interrupt_status);
>> +
>> +     dev_dbg(dev, "Requesting an IRQ...\n");
>> +     /* Request an irq */
>> +     ret = request_irq(pt->pt_irq, pt_core_irq_handler, 0, "pt", pt);
>> +     if (ret) {
>> +             dev_err(dev, "unable to allocate an IRQ\n");
>> +             goto e_pool;
>> +     }
>> +     /* Initialize the ISR tasklet */
>> +     tasklet_init(&pt->irq_tasklet, pt_core_irq_bh,
>> +                  (unsigned long)pt);
>> +
>> +     dev_dbg(dev, "Configuring virtual queues...\n");
>> +     /* Configure size of each virtual queue accessible to host */
>> +
>> +     cmd_q->qcontrol &= ~(CMD_Q_SIZE << CMD_Q_SHIFT);
>> +     cmd_q->qcontrol |= QUEUE_SIZE_VAL << CMD_Q_SHIFT;
>> +
>> +     cmd_q->qdma_tail = cmd_q->qbase_dma;
>> +     dma_addr_lo = low_address(cmd_q->qdma_tail);
>> +     iowrite32((u32)dma_addr_lo, cmd_q->reg_tail_lo);
>> +     iowrite32((u32)dma_addr_lo, cmd_q->reg_head_lo);
>> +
>> +     dma_addr_hi = high_address(cmd_q->qdma_tail);
>> +     cmd_q->qcontrol |= (dma_addr_hi << 16);
>> +     iowrite32(cmd_q->qcontrol, cmd_q->reg_control);
>> +
>> +     dev_dbg(dev, "Starting threads...\n");
>> +     /* Create a kthread for command queue */
>> +
>> +     kthread = kthread_create(pt_cmd_queue_thread, cmd_q, "pt-q");
> Why do you need a thread, you already have a tasklet?
Agreed. This will be taken care in next version of patch set.
>
>
> Okay am stopping here. There are **tons** of style issues with the
> series. For this patch alone checkpatch tells me:
>
> total: 184 errors, 12 warnings, 31 checks, 1593 lines checked
It appears that MS exchange reformatted the patch and the errors are because of Special characters. Now that I am aware of the issue, this will be addressed in next version of patch set.
>
> 1. Please **FIX** the errors
> 2. I suspect tab spaces are wrong (we use 8)
> 3. Read Documentation/process/coding-style.rst, if done, re read it
> again
> 4. Use dmaengine APIs and virtual dma layer
> 5. Dont invent your own stuff, kernel already has stuff to deal with
> most common thngs, no your case is not unique.
> 6. Check other drivers on how to do things
> 7. Make sure you send a series as athread, if in doubt send to yourself!
Sure. All of your suggestion will be addressed in next version of patch set.
>
> Thanks
> --
> ~Vinod

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